Dr. Rob Dillon, Coordinator





Tuesday, June 22, 2021

The American Galba: Sex, Wrecks, and Multiplex

A couple weeks ago [7June21] we reviewed, in some detail, the worldwide fauna of crappy-little amphibious lymnaeid snails that have been referred to the genus [1] or subgenus Galba or Fossaria, or otherwise lumped together under the adjective, “fossarine.”  Now before we go any further, we really must talk about sex.

Did I catch your attention?  That was a cheap trick, sorry.  What I meant is that the extent to which these populations – any of them  – are selfing or outcrossing is critical to our understanding of their evolutionary relationships.  The FWGNA Project endorses the biological species concept.  Asexual reproduction voids the biological species concept and necessitates a retreat to some sort of typological (usually morphological) species concept fraught with subjectivity.

So in recent years, our colleagues have typically relied on microsatellite DNA analysis to estimate the rate of self-fertilization in pulmonate snails.  I hate to get into the details of the technique here, because it’s a miserably-complicated pain in the ass.  Section 3 of the video above will give you some appreciation.

The important thing to know is that by trial, error, hard work and good technique it is possible to work out sets of primers that will amplify regions of highly-repetitive DNA that vary in their copy number, and hence migrate at different speeds on agarose gels, and hence can serve as genetic markers.  These “microsatellites” are inherited in Mendelian fashion, and can be used to estimate heterozygosity, a measure of self-fertilization.

Microsatellite markers are almost as good as the allozyme variants I resolved by starch gel electrophoresis through most of my career, except microsatellites are much more expensive and time-consuming to develop, and you’ll need at least one or two expendable graduate students.  Microsatellites are also more sensitive.  Highly-repetitive regions of DNA have correspondingly-high mutation rates, and with enough microsatellite loci it is possible to “fingerprint” individual organisms, for paternity testing and so forth.  Such fine-scale genetic resolution may be a good thing.  Or not.

So in 2000 a research group led by Sandrine Trouvé of Lausanne with Sylvie Hurtrez-Boussès and a host of colleagues from Montpellier reported microsatellite analysis of seven populations of Lymnaea (Galba) truncatula sampled from Switzerland [2].  They examined variance at nine microsatellite loci in 7 – 26 individuals per population, with an observed overall heterozygosity Ho = 0.029.  Given the expected heterozygosity He = 0.492, Trouvé and colleagues concluded “a reproduction predominantly through selfing certainly constitutes the main cause.” [3]

In 2017 a second microsatellite analysis was published for snails of the subgenus Galba, this involving 13 populations of Lymnaea cubensis sampled across seven Caribbean and South American countries, for a total of 359 individuals.  A Montpellier research group led by Mannon Lounnas, including Pilar Alda and anchored by Sylvie Hurtrez-Boussès [6] analyzed variance at 15 microsatellite loci, most of which demonstrated only a single allele per population.  But in those five populations of L. cubensis where the hypothesis could be tested, He was very significantly lower than Ho, again strongly suggesting self-fertilization.

Maria Dolores Bargues, Santi Mas-Coma, and our friends in Valencia had previously offered direct, experimental evidence of self-fertilization in laboratory populations of Lymnaea (Galba) schirazensis [7].  And in 2018 Mannon Lounnas, the Montpellier gang and many friends, again anchored by Sylvie Hurtrez-Bousses, published a microsatellite analysis confirming predominant self-fertilization in 18 schirazensis populations sampled from all over the world: Peru, Ecuador, Colombia, Venezuela, USA, Spain and Reunion Island, floating in the Indian Ocean off Madagascar, for heaven sake [8].  Although Lounnas and her colleagues prospected for variance at 22 microsatellite loci, 14 of their 18 schirazensis populations demonstrated only 1 allele per locus.  But in those four populations where any genetic variance was found, no heterozygotes were identified, a significant result.

Worldwide Galba [4] from Hubendick [5]

But wait a minute.  Let’s back up a couple steps.  Didn’t we just learn, in our review of [7June21], that G. schirazensis was described from Iran?  Why did the Montpellier group identify those 18 populations of crappy-little amphibious lymnaeids, sampled from all over the world, with the notable exception of anywhere in the Middle East, as Galba schirazensis?

Indeed, on what authority did the Lounnas group identify the 13 populations they sampled in 2017 as G. cubensis?  Or Trouve’s group identify their G. truncatula way back in 2000?

Both of the Lounnas microsatellite studies were squishy-calibrated by direct sequencing and comparison to sequences in Genbank.  For the schirazensis study, the DNA from some small subsample of individuals from 12 of the 18 populations were sequenced for mitochondrial COI and confirmed by 99-100% homology with Iranian sequences deposited in Genbank.  Not ideal, admittedly, but OK.  For the cubensis study, one or two individuals were sequenced at the (nuclear) ITS-2 region from 9 of the 13 populations (sample size was inadequate for four populations), blasted against GenBank, and confirmed by 99-100% homology to the cloud of previously-deposited cubensis, which may have come from anywhere and everywhere, and were in any case identified by consensus of the clueless.

I suppose that Trouvé and her colleagues did not feel that their 2000 study needed standardization, since truncatula is the only Galba whose range includes Switzerland.  But for the record, Muller’s 1774 type locality was in central Germany, 500 km to the north.

We interrupt the orderly unfolding of our narrative for a brief but fiery sermon on definitions, standards, and controls.  My faithful readership will already be well-acquainted with my fixation on type localities.  When Trouvé selected a Galba population from some (unspecified) locality in Switzerland to develop her microsatellite primers, she introduced a 500 km error from Germany.  When Lounnas mixed samples from two Cuban Galba populations with a sample from Guadeloupe to develop her primers, she introduced a 0.33 x 2,000 km error from Cuba.  And when she selected a Galba population from Colombia to develop her schirazensis primers, she introduced a 13,000 km error from Iran.  The errors introduced by these decisions affect not just the individual studies in which they were made but multiply through all subsequent studies that may be built upon them, as we shall see.

So now let’s broach the subject of cross-species amplification.  In addition to testing their microsatellite markers on seven populations of nominal G. truncatula, Trouvé and colleagues [2] also tested one population of the (more distantly related) Lymnaea ovata (aka Lymnaea peregra, aka Radix balthica [9]), finding two of their seven primer pairs to amplify PCR products.  Fine.  Lymnaea ovata (or peregra or balthica) is well-characterized biologically (although not taxonomically) and is just as distinct and easy to identify in Switzerland as L. truncatula.  Its type locality is, admittedly, in France (or Prussia, or Sweden).  But the lymnaeid populations that everybody calls truncatula in Switzerland and the populations that everybody calls ovata in Switzerland are two entirely different things.  So, I’m not sure what I expected, but let’s accept a 2/7 = 29% cross-species amplification figure as reasonable.

More recently, here in the New World, Lounnas and colleagues [6] tested their cubensis primers for cross-species amplification with three other nominal species.  Their sample of the recently-described G. neotropica came from its type locality in Peru (Commendable!) and returned 100% amplification using all 15 primer pairs tested.  Their other outcross controls were considerably less controlish, however.  Their sample of viator came from Frias, Argentina, about 1,500 km north of the type locality at Viedma [10], returning 6/15 =  40% cross-species amplification.  And (if you can believe it) their sample of nominal truncatula came from Peru, at a site approximately 10,000 km W of Germany.  This drives me nuts.  And (for what it is worth) the cross-amplification was 7/15 = 47%.

Bandar Anzali, Iran [7]

What, pray tell, makes Mannon Lounnas and her colleagues identify a population of crappy-little amphibious lymnaeids collected in 2012 from the middle of Peru as the same species O. F. Muller collected in 1774 from the middle of Germany?  You guessed it: DNA squishy-calibration.  They directly sequenced one or two individuals from their Peru population at the ITS-2 locus and found 99% similarity to an (unspecified-European) truncatula sequence previously deposited in GenBank.

Lounnas and a slightly-different set of colleagues [8] also tested their schirazensis primers for cross-amplification with three other nominal species, truncatula from France, viator from Argentina, and cubensis from I-don’t-know-where.  Again, all three of these species were identified by DNA squishy-calibration, four genes this time: 18S, ITS-1, ITS-2, and CO1.  And quite surprisingly, no cross-amplification was observed using 22 schirazensis primer-pairs on DNA from any of these three other species tested whatsoever, nadda, goose egg, zip, 3(0/22) = 0.0.  Really?

Let me get this straight.  Primers that Trouvé and colleagues developed for L. truncatula showed 29% cross-amplification with the very-different Lymnaea ovata, which isn’t even in the subgenus Galba.  And 22 schirazensis primers don’t cross-amplify with any other Galba, ever?  A couple weeks ago [7June21] we learned that schirazensis populations have a peculiarly-variable radula morphology and a peculiar resistance to trematode infection.  Evidence seems to be accumulating that snails nominally identified as “Lymnaea schirazensis” may be strange.  More such evidence will be forthcoming.

The photo labelled “B” above was snapped on the bank of the Taleb Abad River at Bandar Anzali, one of the two sites in Iran from which Bargues and colleagues [7] collected their samples of Lymnaea schirazensis.  Neither site was especially near Shiraz, but in the right country, anyway.  Note how high up the bank the arrows point, even in a relatively arid environment.  I’ve inserted the Bargues figure up there in an effort, probably vain, to keep your attention in an essay that is already far too long and shows no promise of shortening any time soon.

Boring Table 1, abridged [11]
Because in 2018 Pilar Alda, Sylvie Hurtrez-Boussès, and a host of coauthors, including yours truly, published “A new multiplex PCR assay to distinguish among three cryptic Galba species [11],” an understanding of which will be necessary to fully appreciate step #2 in the three-step screening process that Pilar Alda and her 19 colleagues, including yours truly, used to screen the 161 Galba populations we’re fixing to analyze next month [12].

By 2018, looking back over three previous studies, Pili, Sylvie, and the Montpellier gang had accumulated a sum total of 9 + 15 + 22 = 46 primer pairs to amplify DNA microsatellites in crappy-little amphibious lymnaeids of the subgenus Galba.  With that list sitting on her desk, knowing which primers cross-amplified bands from other species, and the sizes of the microsatellite bands they amplified, Pili designed 11 candidate “primer mixes,” each mix including one apparently specific primer pair for each of the three previously-characterized species, truncatula, cubensis and schirazensis.

These eleven primer mixes were tested on 11 “known standards,” five representing the three previously-characterized positive species and six test-negatives, as listed in our abridged (but nevertheless still boring) Table 1 above.  Only one of the 11 “standards” was collected from its type locality [13], the other ten being identified by DNA squishy-calibration, blasting ITS-1, ITS-2, CO1, and 18S sequences to GenBank.  This introduces multi-error into an already multi-multiplex technique, but I have already decried this sin from my pulpit, so see previous.  Ultimately a primer mix was identified yielding distinctly-different microsatellite bands for cubensis, schirazensis, and truncatula, and no PCR products whatsoever for our home-grown Lymnaea (Galba) humilis, or South American viator, or South American cousini.

Screening with that “multiplex PCR assay” became step #2 in the three-step process we’re going to talk about next month.  Admittedly, it is rapid and efficient, facilitating the characterization of a much larger sample size of crappy-little amphibious lymnaeids than would otherwise have been practical.  A sample size of 1,722 snails from 161 different populations, to be precise.

Boring gel photo [11]

But a vivid drawback in the technique immediately presents itself.  Columns 7 – 12 in the gel figured  above look exactly like column #6, the negative control.  So how do we know those columns labelled viator, cousini, and humilis aren’t just plain screw-ups?

And in a larger sense, how reliable is our multiplex PCR assay?  How many assumptions is it based upon?  When the schirazensis primers (for example) were developed for a population of crappy-little amphibious lymnaeids sampled 16,000 km west of its type locality, and tested on a nominal cubensis population sampled 1,000 km north of its type locality, might those be second-order assumptions?  Assumptions squared?  Is the error 17,000 km or 1.6 x 10^7 km?

And (to take another example) when we screen by requiring no amplification for viator, we are assuming that viator is specifically distinct from cubensis, schirazensis, and truncatula, am I right?  Is that a good assumption?  Tune in next time.


Notes:

[1] The FWGNA Project has adopted the “Hubendick compromise” model for the classification of the Lymnaeidae, recognizing Galba as a subgenus of the worldwide genus Lymnaea.  In the present series of essays we have often, however, referred to the nomen Galba as though it were a genus, following the usage of the authors whose work we are reviewing.  See:

  • The Classification of the Lymnaeidae [28Dec06]

[2] Trouvé, S., Degen, L., Meunier, C., Tirard, C., Hurtrez-Boussès, S., Durand, P., Guegan, J., Goudet, J., and Renaud, F. (2000) Microsatellites in the hermaphroditic snail, Lymnaea truncatula, intermediate host of the liver fluke, Fasciola hepatica. Molecular Ecology 9(10): 1662–1664. doi:10.1046/j.1365-294x.2000.01040-2.x.

[3] Predominant (although not exclusive) self-fertilization was subsequently confirmed by several excellent studies.  See:

  • Trouve, S., L. Degen, F. Renaud and J. Goudet (2003)  Evolutionary implications of a high selfing rate in the freshwater snail Lymnaea truncatula.  Evolution 57: 2303 – 2314.
  • Meunier C., S. Hurtrez-Bousses, R. Jabbour-Zahab, P. Durand, D. Rondelaud and F. Renaud (2004)  Field and experimental evidence of preferential selfing in the freshwater mollusc Lymnaea truncatula (Gastropoda, Pulmonata).  Heredity 9: 316 – 322.

[4] This figure is a cut-and-paste of four figures from Hubendick [5] rescaled uniformly.  Lymnaea (Galba) truncatula is figure 306f from Denmark, viator is figure 324 from Brazil, cubensis is figure 310c from St. Thomas, V.I., and humilis is figure 308g from Maine.

[5] Hubendick, B. (1951)  Recent Lymnaeidae.  Their variation, morphology, taxonomy, nomenclature and distribution.  Kungliga Svenska Vetenskapsakademiens Handlingar Fjarde Serien 3: 1 - 223.

[6] Lounnas, M., Vázquez, A.A., Alda, P., Sartori, K., Pointier, J.-P., David, P., Hurtrez-Boussès, S. (2017) Isolation, characterization and population-genetic analysis of microsatellite loci in the freshwater snail Galba cubensis (Lymnaeidae). J. Molluscan Stud. 83: 63–68.

[7] Bargues, M.D., P. Artigas, M. Khoubbane, R. Flores, P. Glöer, R. Rojas-Garcia, K. Ashrafi, G. Falkner, and S. Mas-Coma (2011)  Lymnaea schirazensis, an overlooked snail distorting fascioliasis data: Genotype, phenotype, ecology, worldwide spread, susceptibility, applicability.  Plos One 6 (9): e24567.

[8] Lounnas, M., Correa, A.C., Alda, P., David, P., Dubois, M-P., Calvopiña, M., Caron, Y., Celi-Erazo, M., Dung, B.T., Jarne, P., Loker, E.S., Noya, O., Rodríguez-Hidalgo, R., Toty, C., Uribe, N., Pointier, J.-P., Hurtrez-Boussès, S. (2018) Population structure and genetic diversity in the invasive freshwater snail Galba schirazensis (Lymnaeidae). Can. J. Zool. 96: 425–435.

[9] Hubendick [5] considered ovatus Draparnaud (1805) a simple junior synonym of peregra Muller (1774) and did not consider that Linne’s (1758) nomen balthica is appropriately applied to a lymnaeid.  Subsequent European authors have disagreed.  I don’t want to get involved.  So since Trouvé identified her snails as “Lymnaea ovata,” that’s what we’ll call them.

[10] D’Orbigny gave the type locality of “Var. A” Lymnoeus viator as “oris Patagonensibus” and “Var. B” Lymnoeus viator as “provincia Limacensi (republica Peruviana).”  This was restricted to the Negro River at Viedma, Argentina by Paraense, W.L.  (1976)  Lymnaea viatrix: a study of topotypic specimens.  Rev. Brasil. Biol. 36: 419 – 428.

[11] Alda, Pilar, M. Lounnas, A. Vázquez, R. Ayaqui, M. Calvopiña, M. Celi-Erazo, R. T. Dillon, P. Jarne, E. Loker, F. Pareja, J. Muzzio-Aroca, A. Nárvaez, O. Noya, L. Robles, R. Rodríguez-Hidalgo, N. Uribe, P. David, J-P. Pointier, & S. Hurtrez-Boussès (2018). A new multiplex PCR assay to distinguish among three cryptic Galba species, intermediate hosts of Fasciola hepatica.  Veterinary Parasitology 251: 101-105.  [html]  [PDF]

[12] Alda, Pilar, M. Lounnas, A.Vázquez, R. Ayaqui, M. Calvopiña, M. Celi-Erazo, R.T. Dillon Jr., L. Gonzalez Ramirez, E. Loker, J. Muzzio-Aroca, A. Nárvaez, O. Noya, A. Pereira, L. Robles, R. Rodríguez-Hidalgo, N. Uribe, P. David, P. Jarne, J-P. Pointier, & S. Hurtrez-Boussès (2021) Systematics and geographical distribution of Galba species, a group of cryptic and worldwide freshwater snails.  Molecular Phylogenetics and Evolution 157: 107035. [PDF] [html]

[13] That would be the New York population of Lymnaea (Galba) humilis, of course.  My faithful readership will need no reminder.  But for the rest of you, see:

  • Malacological Mysteries I: The type locality of Lymnaea humilis [25June08]

Monday, June 7, 2021

The American Galba and The French Connection

I do not understand how the United States of America, the richest nation on earth, has fallen so far behind the rest of the world in organismal biology.  Our NASA and our NIH and all those bomb factories run by the DOE are all first-rate, I feel sure.  But when it comes to the biotic majesties of our purple mountains – all the living things that creep under our rocks and crawl through our waters and crowd each other for light from one of our shining seas to the other – we are clueless as Mercedes-full of Kardashians.  Adjusted by GDP, our malacology is shamed by that of Guatemala.

The French National Centre for Scientific Research (CNRS) is the largest basic science agency in Europe, with an annual budget of 3.3 billion euros.  Prominent among their 1,100 research laboratories is the Centre for Functional Ecology and Evolutionary Biology (CEFE) in Montpellier, where a faculty and staff of 282 conduct research on exactly the kinds of scientific questions that we here in America suck at.  Help us, France, you’re our only hope.

I first met Dr. Philippe Jarne of the CEFE at the Society for the Study of Evolution in Snowbird, Utah back in 1993.  But by that point we had already been corresponding for six years.  I still have in my filing cabinet an old-fashioned letter Philippe sent me in 1987, when he was doing his PhD research on the population genetics of Lymnaea peregra [1].  His research was top notch, is top notch, and always has been top notch – using a variety of freshwater pulmonates (e.g., Bulinus, Biomphalaria, Physa) to address questions about mating systems and sex allocation of great generality and importance.  It was Philippe who sent Amy Wethington and me our sample of Physa acuta from France back in 2000 [2].  And I sent him a sample of Lymnaea (Galba) cubensis from here in the Charleston area in 2009, a sample which ultimately played some small role in a paper he and the Montpellier research group published in 2011 [3].

Below is a photo that my daughter snapped at a lunch we enjoyed in Montpellier back in March of 2012, with (from my left) myself, Philippe Jarne, Patrice David, my lovely wife Shary and my French son-in-law Eric.

So on 8Apr15 Philippe emailed me to propose a new collaboration, to “estimate the selfing rate in as many species (of basommatophoran pulmonates) as possible” using a molecular method called RAD-SEQ [4].  Philippe, Tom Janicke, and their collaborators needed about 50 individuals per population from as diverse and as widespread a sample of pulmonates as possible worldwide, the idea being to correlate selfing rates with inbreeding depression.  I told him that I would be happy to help.  I logged many thousand miles on that project through the spring and summer of 2015, covering ten states, ultimately collecting N>50 individuals from 44 populations of 17 pulmonate species [5].  That research effort did not yield results.

I was disappointed by the failure of the Janicke/Jarne project, of course, and I confess, a little bit sore.  But thank heaven, at the opening of the initiative I was able to negotiate along a related line of research that ultimately did yield publishable results, which have now cast considerable light into one of the darker corners of North American freshwater malacology, those crappy little amphibious lymnaeids we here often called “Fossaria,” but which the rest of the world usually calls Galba [6].

In my enthusiastic reply of 8Apr15 I referenced Lymnaea (Galba) humilis, which I offered as a perfect example of North American ignorance regarding pulmonate self-fertilization.  Philippe then let it drop in his follow-up of 10Apr15 that “a PhD student under the supervision of S. Hurtrez here in Montpellier” (who turned out to be Pilar Alda) was even at that date working on “these small Lymnaea, including the infamous schirazensis.”  And so in an email of 13April15, I seized the opportunity to “brainstorm on a tangent.”

The Alda/Hurtrez project to which Philippe was referring was an extension of the 2011 research I mentioned five paragraphs above [3], focused on the Galba of medical and veterinary importance, primarily sampled from South and Central America and the Caribbean.  So I suggested an expansion through North America to include humilis and all the taxa that Hubendick [7] thought synonymous under humilis, but that Burch [8], following Baker [9], had considered separate.  In addition to collecting humilis/modicella from its type locality in New York, I volunteered to collect obrussa from its type locality in Philadelphia, parva from its type locality in Cincinnati, exigua from its type locality in Tennessee, and similar-looking crappy-little amphibious lymnaeid populations from a broad swath of additional muddy riverbanks across the eastern USA.  And on 5May15, Philippe, together with his colleagues Patrice David and Sylvie Hurtrez, agreed.

L. humilis on the margins of Lake Pymatuning, PA

The results of that research have just been published in the April issue of Molecular Phylogenetics and Evolution – a massive work involving 161 populations of Galba and almost as many coauthors [10].  But before I review our findings, I feel as though I should back up and introduce, or in some cases re-introduce, a cast of amphibious little crap-brown snails that has now grown worldwide in scope.  Most of the specific nomina that have been assigned to the lymnaeid subgenus Galba over the last 200 years will be unfamiliar to my North American readership.  Quite a few of those unfamiliar names will, however, become important in the essay I am planning to post next month.

Buccinum truncatulum was described by O.F. Müller in 1774 from Thangelstedt, a village in central Germany.  Populations of Muller’s crappy-little amphibious lymnaeid, which we now classify as Lymnaea (Galba) truncatula, are native to the muddy margins of ponds, rivers, and lakes across Northern Europe and Asia, reportedly extending over the Bering Land Bridge to Alaska, Yukon, and British Columbia.  The species also seems to have been introduced to South America, currently ranging from Chile through Brazil and Peru to Venezuela.  Lymnaea (Galba) truncatula serves as the intermediate host of the sheep liver fluke, Fasciola, and has been the focus of a great deal of research interest, for many years.  The first-marginal teeth on their radular ribbons bear three cusps.  Reproduction is primarily by self-fertilization [11].

The second crappy-little amphibious lymnaeid to reach description worldwide was our own Lymnaeus humilis, authored by Thomas Say (1822).  Populations of L. humilis inhabit the same sorts of marginal habitats as Old World L. truncatula, ranging throughout the United States and Canada.  I was first drawn into the bigtime world of international Galba research in early 2008, when Prof. Dr. Santiago (“Santi”) Mas-Coma of the University of Valencia contacted me about collecting some L. humilis from their type locality here in South Carolina.  Santi and his wife, Maria Dolores Bargues, together with many collaborators, had even by that early date published over 20 papers on fascioliasis and its gastropod vectors worldwide.

Thomas Say did, indeed, receive samples of crappy-little amphibious lymnaeids from the Charleston area in the early nineteenth century, and it does indeed seem likely that samples from Sullivan’s Island (at the mouth of Charleston Harbor) were before him when he described his Lymnaeus humilis.  But it turns out that all our crappy-little amphibious lymnaeids here in the Charleston area have bicuspid first lateral radular teeth, rather than tricuspid, and would today conventionally be identified as Lymnaea cubensis.  So since Say also mentioned “a variety of” his L. humilis at “Oswego” (Owego), New York, I suggested in an essay published on this blog in the summer of 2008 that Say’s humilis type locality be restricted to New York, where the crappy-little amphibious lymnaeid populations are tricuspid [12].

From Bargues et al [13]
Shortly after posting that 2008 essay I drove up to Owego, collected a topotypic batch of L. humilis, and packed them off to my buddy Santi Mas-Coma. The Valencia group then sequenced five DNA markers (CO1, 16S, 18S, ITS-1 and ITS-2) for eight of the snails I collected at that type locality, plus six cubensis individuals I collected from the Charleston area, and developed a manuscript [13], which was never published [14], which was even at that early date becoming a theme of my experience with European research groups.

But let’s back up a couple hundred years and get a fresh start at our historical narrative.  In 1825 Thomas Say redescribed the “Oswego” population as “Lymnaeus modicelles,” and added obrussa from Philadelphia and the subfossil galbana from New Jersey.  Baker [9] respelled that first nomen “modicella” and shifted it to subspecific status under humilis.

Five years later, way down south, Captain P. P. King [16] described Limnaea diaphana from collections made in the Straits of Magellan area, on the first voyage of The Beagle.  That little snail bears a shell indistinguishable from truncatula and humilis, according to Hubendick [7] and Paraense [17].  But the sequence data seem to suggest that L. diaphana is not a Galba, but rather an “archaic relict” stagnicoline [18].  So, let’s set King’s nomen aside.

The next name published in the worldwide literature of crappy-little amphibious lymnaeids was Lymnoeus viator, described by d’Orbigny in 1835 from two places simultaneously, Patagonia (exact locality unspecified) and Peru (Lima), subsequently restricted to the Negro River at Viedma, Argentina by Paraense [19].  Very similar biologically to all the other lymnaeid populations we have reviewed in this essay, the nominal range of L. viator (as conventionally understood) ranges across the bottom of South America from Chile through Argentina to Uruguay. This seems to be the oldest name [20] attached to any population of the subgenus Galba bearing bicuspid first marginal teeth on the radula.  Populations of L. viator can also serve as the hosts of Fasciola which, in some parts of the New World at least, can infect humans as well as livestock.

Shortly thereafter Pfeiffer (1839) described Limnaea cubensis from Cuba, exact locality unspecified.  Populations of this nominal species are conventionally considered to range across the entirety of South and Central America and the Caribbean, overlapping with L. viator in the south, extending into the southern United States, as touched upon five paragraphs above.  Lymnaea (Galba) cubensis is the most important intermediate host of Fasciola in the New World.  Reproduction seems almost exclusively by self-fertilization [11].  The essay I wrote reviewing Charleston-area lymnaeid populations back in 2008 featured a history of L. cubensis, both natural and otherwise, figuring shell and bicuspid radula [12], if you’re hungry for more.

So welcome back to the USA.  In 1841 our old buddy Isaac Lea [21] described Lymnaea parva from Ohio (Cincinnati), L. rustica from Ohio (Poland), L. exigua from Tennessee (unspecified) and L. bulimoides from Oregon (unspecified).  The first three bear three cusps on their first marginal radular teeth and are indistinguishable from humilis in all respects.  But Lea’s nomen bulimoides seems to be the oldest name homegrown here in the USA for crappy little amphibious lymnaeids that have turned out to bear bicuspid first laterals.
From Fig 3 of Correa et al [2]

The dawn of the 20th century saw an explosion of taxonomic activity in the American Lymnaeidae, with Pilsbry, Dall, Baker and Walker adding dozens of nomina, including perpolita, cockerelli, sonomaensis, dalli, cyclostoma, peninsulae, hendersoni, alberta, perplexa, and vancouverensis.  Baker’s (1911) review listed 30 species and subspecies of crappy-little amphibious lymnaeids from North and Middle America,  which he accumulated into Shrank’s (1803) large and inclusive genus Galba [9].  In 1928 Baker [22] split the littlest Galbas into Fossaria (Westerlund 1885), which he divided into tricuspid and bicuspid subgenera, the system essentially adopted by Burch [8].

Back to the Old World one last time, we cannot overlook, as many subsequent authorities most certainly have, Limnaeus schirazensis, described by Küster in 1862 from Shiraz, Iran.  The “infamous” schirazensis, as Philippe termed it, was resurrected in 2011 by Maria Bargues, Santi Mas-Coma, and their coauthors [23] on the basis of DNA sequence distinctions at 18S, ITS-1, ITS-2, 16S and CO1.  Our good friends in Valencia identified schirazensis populations inhabiting eight countries: Iran, Egypt, Spain, Mexico, Venezuela, Ecuador, Peru, and The Dominican Republic, the last five presumably resulting from artificial introduction.

Lymnaea schirazensis populations seem to reproduce almost exclusively by self-fertilization [11].  In habitat, the Valencia group noted that they seem to demonstrate an unusual preference for the land-side of amphibious over the water-side of amphibious.  The situation with the first marginal radular teeth also seems peculiar, “usually bicuspid” but with a “faint tendency” to appear tricuspid in some populations.  And most importantly, from a human standpoint, populations of L. schirazensis are apparently entirely refractory to Fasciola infection.  The Valencia group concluded by suggesting that confusion between refractory schirazensis and susceptible populations of truncatula, cubensis, and viator might have “distorted” data on the incidence of fascioliasis worldwide.

While Küster’s nomen schirazensis was being merely forgotten, Limnaea pictonica, described from Tierra Del Fuego by Rochebraune & Mabille in 1885, was being really most sincerely forgotten [24].  But continuing on to the present day is Jousseaume’s Limnaea cousini, proposed in 1887 to describe a population of crappy-little amphibious lymnaeids in Quito, Ecuador.  Populations of Lymnaea (Galba) cousini bear shells with an unusually-large body whorl and are not generally considered “cryptic” underneath the other crappy-little amphibious lymnaeid populations of South America.  They are also unusual in that they seem to reproduce primarily by outcrossing.  Their radular ribbons demonstrate tricuspid first laterals.  For morphology see Paraense [25], for genetics ask our friends in Valencia [26].

Detail from Baker [8] Plate VII

There were also a bunch of 20th-century nomina proposed by Pilsbry and colleagues for South American populations of crappy-little amphibious lymnaeids that I am simply not going to mention, synonymized by Hubendick [7], rest in peace, all of them.  Two more recently-described South American taxa, neotropica [27] from Lima, Peru and meridensis [26] from Merida State, Venezuela will however play minor rolls in our review next month.

In 1951 Bengt Hubendick, bless his heart, tried to impose some modern order upon this classical mess, lowering hundreds of lymnaeid nomina into synonymy worldwide [7].  In addition to the Holarctic truncatula he recognized humilis, cubensis, and bulimoides from North and Middle America, plus viator, pictonica and cousini from South America, for a total worldwide fauna of seven species of crappy-little amphibious lymnaeids that anybody today might assign to Galba.  And it was Hubendick’s clean, simple model that the FWGNA project adopted in [28Dec06].

Alas, Hubendick’s signal contribution to our understanding of the worldwide Lymnaeidae has been widely ignored.  Burch [8] advocated a seven-species, ten-subspecies, two-subgenus model for North American “Fossaria” based on the work of F. C. Baker [9, 22], and it has been under the Baker/Burch model that most of the USA has labored for 40 years.

Until now, with the help of our French brethren across the seas.  “Le bonheur de l'Amérique est intimement lié au bonheur de toute l'humanité [28].”  Tune in next time.


Notes:

[1] More recently many of our colleagues in Europe have begun referring to Lymnaea peregra as “Radix balthica.”  That the malacofauna of Europe is better known than ours here in North America does not imply that their taxonomy is more stable.  Just exactly the opposite.

[2] Dillon, R. T., A. R. Wethington, J. M. Rhett and T. P. Smith.  (2002)  Populations of the European freshwater pulmonate Physa acuta are not reproductively isolated from American Physa heterostropha or Physa integra.  Invertebrate Biology 121: 226-234.  [PDF]  For more, see:

  • To Identify a Physa, 2000 [6Dec18]

[3] Correa, A.C., J.S. Escobar, O. Noya, L.E. Velasquez, C. Gonzalez-Ramirez, S. Hurtrez-Bousses & J-P. Pointier (2011)  Morphological and molecular characterization of Neotropic Lymnaeidae (Gastropoda: Lymnaeoidea), vectors of fasciolosis.  Infection, Genetics and Evolution 11: 1978-1988.  For a review, see:

  • The Lymnaeidae 2012: Fossarine Football [7Aug12

[4] Rubin, B.E.R., R.H. Ree, and C.S. Moreau (2012)  Inferring phylogenies from RAD sequence data.  Plos One 7(4): e33394. 

[5] Not including Physa acuta!  No audience better than you, the faithful readership of my footnotes, are equipped to appreciate what a challenge it was to collect N>50 individuals from 44 populations of pulmonate snails across 10 American states, representing 17 species, not to include Physa acuta.  And to understand my frustration when that effort yielded nothing, not even an oral presentation, not even an acknowledgment.  So you want to be a scientist, kid? 

[6] The FWGNA Project has adopted the “Hubendick compromise” model for the classification of the Lymnaeidae, recognizing Galba as a subgenus of the worldwide genus Lymnaea [7].  In the series of essays that follows we will often, however, refer to the nomen Galba as though it were a genus, following the usage of the authors whose work we are reviewing.  See:

  • The Legacy of Frank Collins Baker [20Nov06]
  • The Classification of the Lymnaeidae [28Dec06]

[7] Hubendick, B. (1951)  Recent Lymnaeidae.  Their variation, morphology, taxonomy, nomenclature and distribution.  Kungliga Svenska Vetenskapsakademiens Handlingar Fjarde Serien 3: 1 - 223.

[8] This is a difficult work to cite.  J. B. Burch's North American Freshwater Snails was published in three different ways.  It was initially commissioned as an identification manual by the US EPA and published by the agency in 1982.  It was also serially published in the journal Walkerana (1980, 1982, 1988) and finally as stand-alone volume in 1989 (Malacological Publications, Hamburg, MI).

[9] Baker, F. C. (1911) The Lymnaeidae of North and Middle America, Recent and Fossil. Special Publication, no. 3. Chicago: Chicago Academy of Natural Sciences.

[10] Alda, Pilar, M. Lounnas, A.Vázquez, R. Ayaqui, M. Calvopiña, M. Celi-Erazo, R.T. Dillon Jr., L. González Ramírez,  E. Loker, J. Muzzio-Aroca, A. Nárvaez, O. Noya, A. Pereira, L. Robles, R. Rodríguez-Hidalgo, N. Uribe, P. David, P. Jarne, J-P. Pointier, & S. Hurtrez-Boussès (2021) Systematics and geographical distribution of Galba species, a group of cryptic and world-wide freshwater snails.  Molecular Phylogenetics and Evolution 157: 107035. [pdf] [html]

[11] I am currently drafting a separate essay on the subject of asexual reproduction in crappy-little amphibious lymnaeids of the subgenus Galba, to be posted in the near future.  For now, here are the key references:  Trouvé, S. et al. (2000) Microsatellites in the hermaphroditic snail, Lymnaea truncatula, intermediate host of the liver fluke, Fasciola hepatica. Molecular Ecology 9(10): 1662–1664.  Trouvé, S. et al. (2003)  Evolutionary implications of a high selfing rate in the freshwater snail Lymnaea truncatula.  Evolution 57: 2303 – 2314.  Meunier C. et al. (2004)  Field and experimental evidence of preferential selfing in the freshwater mollusc Lymnaea truncatula (Gastropoda, Pulmonata).  Heredity 9: 316 – 322.  Lounnas, M. et al. (2017) Isolation, characterization and population-genetic analysis of microsatellite loci in the freshwater snail Galba cubensis (Lymnaeidae). J. Molluscan Stud. 83: 63–68.  Lounnas, M. et al. (2018) Population structure and genetic diversity in the invasive freshwater snail Galba schirazensis (Lymnaeidae). Can. J. Zool. 96: 425–435.

[12] For a detailed review of the cubensis/humilis situation here in the Charleston area, with notes on morphology and natural history, see:

  • Malacological Mysteries I: The type locality of Lymnaea humilis [25June08]

[13] Bargues, M.D., P. Artigas, R.T. Dillon, Jr., and S. Mas-Coma (unpubl) Fascioliasis in North America: Multigenic characterization of a major vector and evaluation of the usefulness of rDNA and mtDNA markers for lymnaeids.

[14] Here’s a quote from a Mas-Coma email of 26may11: “You cannot imagine the problems originated by your sending of L. cubensis from Sullivan island to the French Jean- Pierre Pointier!!! He did publish his results before we did! […] They even used our sequences of L. humilis taken from GenBank even if we did not yet publish them. And of course they never mention that these sequences are ours, but write the article in a manner [15] that the reader believes that these sequences were made by them!!”

[15] To be fair.  Correa, Hurtrez-Boussès, Pointier and the Montpellier group did cite the GenBank accession numbers for our humilis sequences from Owego, which if one refers to GenBank, are attributed to Bargues/Mas-Coma.  It is my impression that this is a general problem with the GenBank system – secondary researchers mining and publishing research based on sequences which the primary authors may not have as yet published.

[16] King, P.P. (1830) Description of the Cirripeda, Conchifera and Mollusca in a collection formed by the Officers of the HMS Adventure and Beagle employed between the years 1826 and 1830 in surveying the southern coasts of South America, including the Straits of Magalhaens and the Coast of Tierra del Fuego Zoological Journal 5, Article 47: 332- 349.

[17] Paraense WL 1984. Lymnaea diaphana: a study of topotypic specimens (Pulmonata: Lymnaeidae). Mem Inst Oswaldo Cruz 79: 75-81.

[18] Bargues, M.D., R. L.M. Sierra, P. Artigas, and S. Mas-Coma (2012)  DNA multigene sequencing of topotypic specimens of the fascioliasis vector Lymnaea diaphana and phylogenetic analysis of the genus Pectinidens (Gastropoda).  Mem Inst Oswaldo Cruz 107: 111 – 124.

[19] Paraense, W.L. (1976)  Lymnaea viatrix: a study of topotypic specimens.  Rev. Brasil. Biol. 36: 419 - 428.

[20] Paraense suggested that d’Orbigny’s 1835 nomen be respelled as “viatrix” to agree in gender with the feminine “Lymnaea.”  In March of 2019 I asked our good friend Harry Lee for a ruling on this usage.  Harry replied that d’Orbigny’s specific epithet is not an adjective, rather “it is clear from the Latin (and French; see d'Orbigny, 1837: 340) that ‘viator’ is an appositive (an unambiguous noun; like viatrix) and should not be declined to agree with the gender of any combining generic epithet.”  Harry concluded that Paraense’s respelling is an “unjustified emendation in the language of the Code, and an unavailable name under its provisions. By coincidence, I think the same relationship holds for Lymnaea and Lymnoeus!”

[21] Lea, Isaac (1841) On fresh water and land shells.  Proceedings of the American Philosophical Society 2: 30 – 34.  Proc. Amer. Philos. Soc. II, 30 – 34.

[22] Baker, F.C. (1928)  The Fresh Water Mollusca of Wisconsin, Part I, Gastropoda.  Bulletin 70 of the Wisconsin Geological and Natural History Survey.  507 pp.

[23] Bargues, M.D., P. Artigas, M. Khoubbane, R. Flores, P. Glöer, R. Rojas-Garcia, K. Ashrafi, G. Falkner, and S. Mas-Coma (2011)  Lymnaea schirazensis, an overlooked snail distorting fascioliasis data: Genotype, phenotype, ecology, worldwide spread, susceptibility, applicability.  Plos One 6 (9): e24567.

[24] Lymnaea pictonica (Rochebraune & Mabille 1885) may be a synonym of L. diaphana.  See Bargues et al. (2012) from note [18].

[25] Paraense W.L. 1995. Lymnaea cousini Jousseaume, 1887, from Ecuador (Gastropoda: Lymnaeidae). Mem Inst Oswaldo Cruz 90: 605-609.

[26] Bargues, M.D., Artigas, P., Khoubbane, M., Mas-Coma, S., 2011. DNA sequence characterisation and phylogeography of Lymnaea cousini and related species, vectors of fascioliasis in northern Andean countries, with description of L. meridensis n. sp. (Gastropoda: Lymnaeidae). Parasites & Vectors. 4 (132).

[27] Bargues, M.D., Artigas, P., Mera y Sierra, R., Pointier, J.-P., Mas-Coma, S., 2007. Characterisation of Lymnaea cubensis, L. viatrix and L. neotropica n. sp., the main vectors of Fasciola hepatica in Latin America, by analysis of their ribosomal and mitochondrial DNA. Ann. Tropical Med. Parasitology 101:621–641.

[28] Usually translated as, “The good fortune of America is closely tied to the good fortune of all humanity.”  From a letter written home by the Marquis de Lafayette, as he sailed toward blockaded Charleston in 1777.

Friday, May 7, 2021

Fun with Campeloma!

Editor’s Note: The essay that follows is the third in a three-part series on the systematics and taxonomy of viviparid gastropods.  I’d recommend that you back up and read my essays of [9Mar21] and [5Apr21] before going forward, if you haven’t already.

Hey boys and girls!  Want to match wits with an international team of 16 professional scientists?  Click the picture below and download our keen quiz #1!

The figure shows representative shells from the six species of North American Campeloma sequenced by Dr. Björn Stelbrink and his colleagues for their worldwide viviparid gene tree [1].  If you click it, you can download a pdf circular that also reprints the Burch/Vail dichotomous key [2] that Dr. Björn and his team used to identify the snails that bore those six shells.  How many can you get right?  The answers were hidden in our March essay, posted [9Mar21].

Keen Campeloma Quiz #1

So now kids, do you think you’ve got what it takes for an exciting career in the fast-growing field of freshwater gastropod Malacology?  Are you looking for a role model?  Look no further than the example set by our colleague Dr. Steven G. Johnson, currently Dean of the College of Science at the University of New Orleans [3].  The 13 papers he published on the evolutionary biology of Campeloma 1992 – 2007 are as good as any body of work on any malacological topic anywhere, ever.  I’ve listed my favorites at footnote [4] below.

Over that 16-year period, Dr. Steve brought a variety of techniques – allozyme electrophoresis, flow cytometry, mtDNA sequencing – to bear on the evolutionary relationships among dozens of populations of Campeloma, initially sampled throughout the eastern US, then subsequently focused on a sweeping arc of Atlantic and Gulf drainages from South Carolina to Louisiana.  He documented, quite thoroughly and beautifully, multiple origins of parthenogenesis in these populations – sometimes spontaneously by autodiploidy and sometimes by allotriploidy, through hybridization and backcrossing.

The grayscale background of the figure below shows the study area for a 1999 paper that Dr. Steve published with Eric Bragg [4].  He assigned these particular 31 Campeloma populations [5] to five specific nomina using the same Burch/Vail dichotomous key that you used for Keen Quiz #1, with an eye toward type localities.  So populations inhabiting the Wekiva River drainage must be C. floridense by definition, and populations inhabiting the Ochlockonee must be C. parthenum Campeloma limum was described from South Carolina, so that name would be appropriate for Atlantic drainages, and C. geniculum was described from the Flint River, so appropriate for Gulf drainages [6].  The assignment of Say’s specific nomen Campeloma decisum to populations west of the Mobile Basin was a vanilla call, by shell only.

It is interesting to notice that at no point in no body of water ever sampled by Dr. Steve Johnson during his entire 16 year career did more than a single nominal species of Campeloma occur sympatrically.  Where (sexual) C. limum populations and (sexual) C. geniculum populations have apparently come into contact, he found parthenogenic populations which he identified by a third name, C. parthenum.

Johnson & Bragg Fig 1, Stelbrink mapped in red

So, Johnson & Bragg sequenced the mitochondrial cytB gene for 1 – 5 snails sampled from each of these 31 populations.  Their mtDNA gene tree (maximum parsimony) showed six distinct C. parthenum sequences (and one for C. floridense) scattered haphazardly inside a large C. limum cluster, with C. geniculum on one outside branch and C. decisum on another.  Nominal decisum and nominal geniculum are apparently separated by a big, beautiful discontinuity of some sort at the Mobile Basin, but Dr. Steve’s data did not address whether that barrier is reproductive or merely geographical.

Which brings us back to Dr. Björn Stelbrink’s study of worldwide viviparid phylogeny with which we kicked off this essay [1].  Because Dr. Björn’s little sample of six nominal Campeloma species, marked in red on the map above, was centered on the Mobile Basin and North Alabama, right where Dr. Steve Johnson mapped his mysterious discontinuity.  And although Dr. Björn’s group only analyzed single snails from single populations for each of those six species in the old-school U1S2NMT3 gene tree we reviewed in March, reference back to his team’s supplementary table S1 reveals that sometimes they actually sequenced two.

So the map above shows samples from two populations of C. decisum, two populations of C. decampi, and two populations of C. regulare, as well as singletons for parthenum, geniculum and limum.  All nine of these individual snails were identified using the same Burch/Vail key everybody has used for 40 years and sequenced for three genes [7].  And this suggests a test.

If the morphological characters upon which the Burch/Vail key was based fairly reflect the evolutionary history of the Campeloma populations which bear those shells on their backs, one would expect the two snails that Dr. Björn identified as decisum1 and decisum2 to be the most similar to each other genetically, and ditto for the two snails identified as decampi1 and decampi2, and ditto for regulare1 and regulare2.

The figure below is a simple neighbor-joining network generated by the software inside GenBank, connecting the nine CO1 sequences deposited by Dr. Björn Stelbrink for his six nominal species of Campeloma, with the nearest neighbor for each of the six test snails identified by a red arrow.

Of the six nearest-neighbors, only one matched correctly.  The nearest neighbor of decisum1 was in fact decisum2 (98.5% sequence identity).  But oddly, the nearest neighbor of decisum2 was not decisum1, but rather decampi2, with which it demonstrated 99.1% identity.  And further, the nearest neighbor of decampi2 was not decampi1 (by a long shot), but mutually with decisum2.  The nearest neighbor of decampi1 was decisum1, as was the nearest neighbor of regulare1 as was the nearest neighbor of regulare2.  In fact, of the six CO1 sequences obtained for nominal species pairs, only the one sequence, that of decisum1, correctly matched its sister.

Neighbor-joining network from Stelbrink [1] COI sequences

Turning now to the two nuclear genes sequenced by Dr. Björn’s team, very little variance was apparent among the nine sequences for either, none correlating with the taxonomy.  In the histone H3 data set (328 bp), the pair of decisum sequences matched each other and the singleton parthenum sequence.  That group of three differed by a single A/G transition at position 262 from a group that contained both decampi sequences and both regulare sequences.  The limum sequence and the geniculum sequence were both a bit more distinctive, differing from each other (and from the decisum group) by four transitions.

For 28S data set (1,058 bp) the two decisum sequences were again identical to each other, to the parthenum, and to one of the regulare.  The other regulare differed by a single A/G transition at residue 535 and the geniculum differed by a single C/T transition at residue 833.  The two decampi were also again identical to each other and (this time) to the single C. limum sequence.  That set of three differed from the decisum cluster by a two-nucleotide indel at positions 835-6, which is surprising, especially given the geography, and I think significant.  There most certainly is some genetic structure to this set of 3x9 DNA sequences, but the 19th-century taxonomy is not capturing it.

Hey kids, are you ready for some more fun?  Now’s the time to try Keen Quiz #2, shown on page 3 of that same pdf circular you downloaded at the beginning of this essay.

Can you find the three secret-decoder Campeloma hidden in the weeds?  Now can you identify those three shells using the Burch/Vail key?  Circle each shell and write what you think it is in the spaces provided.  Answers below, no peeking!

Not uncommonly, when I am casting about for larger analogies to apply to the messy evolutionary biology of freshwater gastropods, I find myself looking toward the botanical, rather than to the zoological [8].  And in the case of North American Campeloma, I have found inspiration in the dandelions.

Keen Campeloma Quiz #2
The reproductive biology of dandelions is as diverse as one could possibly imagine – outcrossing, selfing, parthenogenetic cloning, sexual/asexual cycling, everything.  An elaborate taxonomy built up in nineteenth-century Europe to describe all the morphs, forms, subspecies and sections of dandelions, but today, most botanists refer the entire yellow-blooming, blowball-sprouting mess to Taraxacum officinale, because after a couple hundred years of squinting at them and screwing around with them, all dandelions pretty much look alike.

The widespread incidence of parthenogenesis in North American populations of the viviparid genus Campeloma voids the biological species concept and necessitates a retreat to the morphological.  And since (judging from the work of Johnson and Stelbrink) there are apparently no consistent phenotypic characters, shell morphological or otherwise, by which Campeloma populations can be distinguished, the FWGNA Project will refer all populations of Campeloma to the oldest available specific nomen, Campeloma decisum (Say 1817).

But how about inconsistent characters?  Nothing in the paragraph above should be interpreted as foreclosing the recognition of C. decisum subspecies – geographically separate and morphologically different forms – even if they intergrade, even if there is no genetic basis for the distinction [9].  The shell morphology of Campeloma populations most certainly does vary regionally.  Indeed, big rivers of the American interior are often inhabited by populations of Campeloma bearing distinctly heavy shells, which have traditionally been identified as C. crassulum Rafinesque 1819, almost certainly a case of cryptic phenotypic plasticity [10].  The FWGNA Project recognizes these populations at the subspecific level, as C. decisum crassulum, just as we recognize heavily-shelled Pleurocera canaliculata canaliculata in those same big rivers, and more gracile P. canaliculata acuta in the little streams that feed into them.

And certainly Call’s (1886) floridense could be saved as a subspecies name for C. decisum with brown apertures, right?  And Binney’s (1865) decampi also seems a likely candidate for retention at the subspecies level.  Although I have no personal observations to contribute, the figures and photos I have seen (e.g., shell #1 way up above) seem to suggest that Campeloma populations in North Alabama may indeed bear shells that are atypically slender and higher-spired, likely for ecophenotypic reasons we do not understand.  And the nomen “decampi” has appeared in recent literature connected to some conservation concerns [12].

As we have often pointed out when faced with analogous situations in the North American pleurocerids, the Latin nomina assigned to biological populations may bear an important indexing function, as well as evolutionary significance.  So, in addition to crassulum and floridense and (perhaps) decampi, it would be a shame to see the names that Dr. Steve Johnson used for his important works – geniculum (Conrad 1834), limum (Anthony 1860), and parthenum Vail 1979 – forgotten by the google machine.  Those names have been useful to index Campeloma populations across the southeastern United States for quite a few years now.

But here’s a big problem, kids.  And maybe you can help!  Let’s look at how you did on Quiz #2.  Those secret-decoder shells didn’t have brown apertures, did they, so they are not floridense.  Did you think that their whorls have angled shoulders, or are their shoulders rounded, or do they have no shoulders at all?  Angled?  So are those shells broadly ovate or narrowly ovate?  Are they Campeloma limumCampeloma geniculum?  Did any of you guess Campeloma decisum for any of the secret-decoders?

Surprise!  All three of the shells hidden in the dandelion patch above are topotypic Campeloma decisum, collected from a pond in Philadelphia’s Fairmount Park, along the banks of the Schuylkill River, where Thomas Say almost certainly explored in 1817.  The snails that bore those three shells were C. decisum, by definition.

That makes them what scientists call a “control,” and what kids like us call super-duper secret-decoders.  Every other Campeloma population, bearing every other shell shape, form, or size, that anybody has ever seen, are (scientifically-speaking) unknown.  That includes all nine of those populations identified by Dr. Björn Stelbrink’s team we had fun with in Keen Quiz #1, and all 31 of those populations studied by Dr. Steve Johnson.  If Dr. Björn’s shells and Dr. Steve’s shells look like the secret-decoders, their correct identification is C. decisum, by definition.  Only if they look different, can they be identified as anything else.

Did Jack Burch and Virginia Vail look at secret-decoders first, when they were making their 1982 dichotomous key?  I don’t know.  The University of Michigan Museum of Zoology does (indeed) hold a couple lots of Campeloma decisum collected from the Schuylkill River in Philadelphia, so it is possible.  But I don’t know about you, kids, I cannot make the Burch/Vail key work at all.  I get messed up early, way up at couplet 14, because I really think that at least some of our secret-decoder shells demonstrate “angled” shoulders, which sends me down the wrong path.

So it would be great to save Dr. Steve Johnson’s limum, geniculum, and parthenum as subspecies names, it really would.  But even setting aside the Burch/Vail key, I cannot distinguish limum collected from its type locality (“South Carolina”) and control decisum from Philadelphia.  Could I distinguish geniculum or parthenum from decisum/limum?  I don’t know that, either [13].  I don’t have control collections from the Flint River or Lake Talquin, or really anywhere in the Gulf drainages of Georgia and Florida.

Boys and girls, I’m going to leave this challenge to you all, the next generation of malacologists. Here’s what I want you to do.  Mail your completed quiz sheets to “Fun With Campeloma,” P.O. Box 31532, Charleston, SC 29417.  Don’t forget to include your name and address and $1.25 for postage and handling.  No, I won’t grade them – I don’t know the right answers myself.  But all entries will be entered into a random drawing.  And one lucky winner will get a genuine FWGNA deputy’s badge and a license to classify the subspecies of Campeloma decisum throughout North America any way he or she wants.

But one last warning, kids, before we sign off this month.  You may hear some grown-ups asking why we have to fall back to an 18th century morphological species concept, as I so boldly asserted ten paragraphs above.  Accepting that the biological species concept is void for Campeloma, those grown-ups may be suggesting that we move forward to the phylogenetic species concept, or one of those other recent concepts based on gene trees.  Don’t all the genetic data we have reviewed this month suggest some sort of evolutionary structure to these populations?  Surely all the Campeloma populations spread across half of North America aren’t equally related to each other, are they?  DNA sequences and fancy tree-generating algorithms are a more scientific way to name snail populations than some kid’s subjective judgement calls on fat brown shells, right?

Be careful around grown-ups like that, boys and girls!  They’re not malacologists, they’re phylogenetic systematists!  We’re going to learn a lot more about phylogenetic systematics in the next few months, and why ideas like that don’t hold water.  So stay tuned!


Notes:

[1] Stelbrink, B., R. Richter, F. Köhler, F. Riedel, E. Strong, B. Van Bocxlaer, C. Albrecht, T. Hauffe, T. Page, D. Aldridge, A. Bogan, L-N. Du, M. Manuel-Santos, R. Marwoto, A Shirokaya, and T. Von Rintelen (2020)  Global diversification dynamics since the Jurassic: Low dispersal and habitat-dependent evolution explain hotspots of diversity and shell disparity in river snails (Viviparidae).  Systematic Biology 69: 944 – 961.

[2] This is a difficult work to cite.  J. B. Burch's North American Freshwater Snails was published in three different ways.  It was initially commissioned as an identification manual by the US EPA and published by the agency in 1982.  It was also serially published in the journal Walkerana (1980, 1982, 1988) and finally as stand-alone volume in 1989 (Malacological Publications, Hamburg, MI).

[3] Rule #1 is, stay out of museums! Those musty cabinets of dusty shells will kill your scientific career faster than a confession of the Apostle’s Creed.  And Rule #2 is, never return emails from anybody who ever has.

[4] Johnson, S. G. 1992. Spontaneous and hybrid origins of parthenogenesis in Campeloma decisum (freshwater prosobranch snail). Heredity 68:253-261.  Johnson, S.G., R. Hopkins, and K. Goddard. 1999. Constraints on elevated ploidy in hybrid and non-hybrid parthenogenetic snails. Journal of Heredity 90: 659-662.  Johnson, S.G. and W. Leefe. 1999. Clonal diversity and polyphyletic origins of hybrid and spontaneous parthenogenetic Campeloma (Gastropoda: Viviparidae) from the southeastern United States. Journal of Evolutionary Biology 12:1056-1068.  Johnson, S.G. and E. Bragg. 1999. Age and polyphyletic origins of hybrid and spontaneous parthenogenetic Campeloma (Gastropoda: Viviparidae) from the southeastern United States. Evolution 53:1769-1781.  Johnson, S.G. 2000. Population structure, parasitism and survivorship of sexual and parthenogenetic Campeloma limum (Gastropoda: Viviparidae). Evolution 54:167-175.  Johnson, S. G., 2005. Mode of origin differentially influences the fitness of parthenogenetic freshwater snails. Proc. Roy. Soc. Lond. B. 272: 2149-2153.  Johnson, S. G. 2006. Geographic ranges, population structure and ages of sexual and parthenogenetic snail lineages. Evolution 60:1417-1426.

[5] The 1999 paper by Johnson with W. R. Leefe surveyed 55 populations.  The Johnson & Bragg paper from which the figure was extracted retained the Johnson & Leefe numbering system but focused on a slightly-less-cluttered 31-population subset.

[6] Johnson never sampled the Flint River proper, up in Georgia, where it comes in close contact with the Ocmulgee R., which drains east to the Atlantic.  This would certainly have been intellectually fascinating, and might well have clarified Campeloma taxonomy substantially, and the omission drives me nuts, absolutely nuts.

[7] The Stelbrink team sequenced mitochondrial CO1 and nuclear 28S and H3.  They did not (alas) sequence mitochondrial cytB, so their data cannot be integrated with that of Steve Johnson.

[8] The most obvious example is my “USR” model for life history evolution in the freshwater mollusks, which I patterned after J. P. Grimes” CSR model for the plants: Competitors, Stress-tolerators, and Ruderals.  That idea was the unifying theme of my (2000) book for Cambridge University Press.  I thought it would make me rich and famous.  I wonder why not.

[9] To refresh your memory on the definition of the word, “subspecies,” see:

  • What Is a subspecies? [4Feb14]
  • What Subspecies Are Not [5Mar14]

[10]  Quoting Dillon and colleagues [11], “phenotypic plasticity may be considered cryptic when intrapopulation morphological variance is so extreme as to prompt an (erroneous) hypothesis of speciation.”  To refresh your memory:

  • Pleurocera acuta is Pleurocera canaliculata [3June13]
  • Pleurocera canaliculata and the process of scientific discovery [18June13]
  • Elimia livescens and Lithasia obovata are Pleurocera semicarinata [11July14]

[11] Dillon, R. T., S. J. Jacquemin & M. Pyron (2013) Cryptic phenotypic plasticity in populations of the freshwater prosobranch snail, Pleurocera canaliculata.  Hydrobiologia 709: 117-127. [PDF]

[12] Haggerty, T.M. and J.T. Garner (2008)  Distribution of the armored snail (Marstonia pachyta) and slender Campeloma (Campeloma decampi) in Limestone, Piney, and Round Island Creeks, Alabama.  Southeastern Naturalist 7: 729-736.  Haggerty, T.M., J.T. Garner and L. Gilbert (2014)  Density, demography, and microhabitat of Campeloma decampi (Gastropoda: Viviparidae). Walkerana 17: 1 – 7.

[13] But reading all the way down through the Burch/Vail key to couplet #19, one gets the strong impression that even Virginia Vail could not distinguish her Campeloma parthenum from Campeloma decisum.  The basis for the decisum/parthenum distinction is geographical only.  If you find it in the Ochlockonee River, it’s parthenum.  Otherwise, it’s decisum.  So parthenum is an allotriploid hybrid of nominal limum and geniculum, which Burch/Vail distinguished from decisum/parthenum by that problematic shoulder-shape couplet #14?   So two nominal species with angled shoulders hybridize to form populations with rounded shoulders?  Hmmm.  That’s as far down this rabbit hole as I care to go, even in a discursive footnote.

Monday, April 5, 2021

Bill and Ruth and Jack and Virginia, and Campeloma

Bill Clench was already well into the mascot phase of his career when I first met him at the 1976 AMU meeting in Columbus, Ohio.  Colleagues, students, and friends ushered him front-row-center for the annual society photo, Joe Morrison [1] and Leslie Hubricht [2] trailing in his wake.  I found Dr. Clench to be a warm and outgoing gentleman, still alert at age 78.  Please Lord, take me home before anybody calls me “alert.”

William J. Clench was born in New York in 1897 and grew up in the Boston area, collecting bugs, snails and shells around the Fenway, the Blue Hills and the local beaches [3].  Charles W. Johnson, the noted marine malacologist at the Boston Society of Natural History, was an early influence.  Clench graduated from Michigan State University in 1921, earned his MS at Harvard in 1923, then moved on to the University of Michigan to work on his doctorate [4], where Bryant Walker, quoting Tucker Abbott’s remembrance [5], “lit the malacological fires within Bill and was largely responsible for his first love, the freshwater mollusks.”

American Malacological Union 1976 [6]

From Michigan Clench accepted the mollusk curatorship at Harvard’s Museum of Comparative Zoology, where he served for 40 years, 1926 – 1966, mentoring many students who would become quite influential themselves.  Clench’s most famous student was R. Tucker Abbott, who succeeded Henry Pilsbry as curator at the ANSP and editor of The Nautilus, but we should not fail to mention the unionid guys Dick Johnson and Sam Fuller, or Arthur Clarke, whose landmark work on the Canadian freshwater molluscan fauna [7] sits handy by my desk, here 40 years after its publication.

Clench’s bibliography lists 420 scientific papers, covering the breadth of malacology: marine, terrestrial, freshwater and fossil, focused on North America but ultimately worldwide [8].  Most of his better papers were coauthored by Ruth Turner, another former student, with whom Clench’s life was “entwined,” to borrow Dick Johnson’s carefully-chosen verb.  We have previously featured on this blog the 1956 Clench and Turner monograph on the freshwater mollusks of Florida/Georgia Gulf drainages [9], which was an important contribution.

Clench’s malacology was early-modern, rooted in the old typology but with a growing appreciation of genetic variation within and among populations.  Looking down from my 2021 freshwater-gastropod-centric perspective, his greatest contribution was his two-part series on the North American Viviparidae, published in 1962 [10] and (with Sam Fuller) in 1965 [11].

The taxonomic history of the North American Viviparidae is identical to the taxonomic history of the North American Pleuroceridae, minus one order of magnitude coming into the 20th century, and two going out [12].  Digging through the musty tomes on the shelves and the dusty shells in the cabinets of the MCZ in the early 1960s, Clench was able to uncover 49 Latin nomina assigned to the genus Campeloma, Isaac Lea [14] tying C.S. Rafinesque for the lead with six each.  Of those 49 nomina, 35 he discarded for cause or synonymized, little rationale given or expected, at the close of the era when such good works were still possible.  Clench did not preface his work with an exhaustive study of shell morphological variation, as did my hero Calvin Goodrich for the North American pleurocerids in the 1940s [15].  But I don’t think he missed any viviparid nomina either, as Goodrich simply skipped hundreds of pleurocerids.  I think Clench got them all.  Thank you, Bill.

Alas, Clench did not explain why he spared the 14 specific Campeloma nomina that survived his 1962 monograph, any more than he explained why he cut the other 35.  That burden was shouldered 20 years later by Dr. John B. Burch [16], with an obscure contribution from Dr. Virginia A. Vail.

From the Burch/Vail key [16]

The “Family Viviparidae” header in Burch’s dichotomous key, way back on page 227, carries an asterisk.  And at the bottom of page 227 is printed, “*From Burch & Vail (1982).”  But no work by Burch & Vail is listed among the references, nor was one ever published subsequently, to my knowledge [17].

Burch’s bibliography does, however, list six papers published by Virginia Vail at that point in her career, all solo, and they are good ones.  She was an excellent scientist, about whom I have been able to discover little.  She was born in Schenectady, NY, in 1945, earned her B.A. at Hartwick College (NY) and her M.S. and Ph.D. at Florida State University, graduating in 1975 [18].  From thence Vail went directly to the Tall Timbers Research Station north of Tallahassee, where she spent the rest of her career.

In 1977 and 1978 Virginia Vail published a two-part series comparing the reproductive anatomy and life history of Campeloma, Lioplax, and Viviparus in Florida.  Her first paper [19] was anatomical, featuring very nice drawings of male and female reproductive systems for all three taxa, and her second paper [20] ecological, detailing seasonal reproductive cycles.  The viviparids are quite conservative anatomically; Virginia was able to document only negligible difference in the plumbing of the three genera [21].  But here 40 years later, we still await a finer contribution to the comparative biology of the North American Viviparidae.

Virginia Vail identified the Campeloma population she selected for her study as C. geniculum (Conrad).  Interestingly, that particular population, inhabiting the Chipola River about 60 miles NW of Tallahassee, seems to have been entirely sexual, males and females (apparently) in roughly equal proportion.  She made only passing reference to asexual reproduction in her 1977-78 papers, noting that Mattox [23] had documented parthenogenesis in Campeloma rufum [24] as early as 1937.

Vail [19] figs. 5 & 10 [25]

The next year, Vail described Campeloma parthenum from Lake Talquin, an impoundment of the Ochlockonee River west of Tallahassee.  She distinguished that population both by its apparent absence of males and by the contour of the outer lip of the shell [26].  But she seems to have been struggling with species concepts, even as she was describing new ones.  Here is the title and abstract of the talk she gave at the August 1979 meeting of the American Malacological Union in Corpus Christie, TX:

“CHAOS IN THE GENUS CAMPELOMA (GASTROPODA: VIVIPARIDAE)

A poor understanding of environmentally induced shell variation, anatomical characteristics and the animal’s biology makes species identification difficult.  The occurrence of both dioecious and parthenogenetic populations (races? species?) and their peculiar geographic distributions further complicate the problem.  Observations on southeastern populations are offered to illustrate the problem and suggest solutions.”

I could not have said that better myself.  Fascinatingly, this was neither the title nor the abstract ultimately published in the Bulletin of the American Malacological Union for 1979, page 67.  The version that saw print was much more tamely entitled, “The Species Problem in Campeloma,” and featured a relatively measured critique of reliance on shell character, noting “the fact that reproduction can occur either parthenogenetically or sexually.”  As of the publication of her 1979 abstract, Virginia Vail was only counting two Campeloma species in Florida and Georgia combined, C. geniculum and “C. limum (includes C. floridense).”

I seem to remember [27], here 40 years later, that the solution Virginia Vail suggested on that August morning at La Quinta Royale Hotel in Corpus Christie, TX, recognized just those two species, a heavily-shelled C. geniculum (sexual) and more lightly-shelled C. limum (parthenogenetic).  That was certainly the direction Fred Thompson was tending by the 1990s with his “Identification Manual for The Freshwater Snails of Florida [30].”  Thompson listed four Campeloma species for The Sunshine State (geniculum, limum, floridense and parthenum), but observed, “in view of the inconsistency of shell characters, these last three forms may represent only a single species, Campeloma limum.”

American Malacological Union 1979

But returning to the thread of our story.  It was sometime during the late 1970s that Jack Burch signed a contract with the EPA to deliver his illustrated key to the North American Freshwater Snails [16].  And somehow [31] he linked up with Virginia Vail, during the full flower of her career.

The Burch/Vail key to the North American Viviparidae that ultimately saw publication in 1982 proceeds unremarkably through its first ten couplets, guiding us to the genus Campeloma on page 228, where we are referred to supplemental note (4).  That endnote – on page 268 now – begins with a brief review of Clench’s signal (1962) contributions to our understanding of the genus Campeloma [10].  Then four more nomina are subtracted from Clench’s list of 14 species on the authority of Arthur Clarke [32]: leptum Mattox 1940, tannum Mattox 1940, integra (Say 1821) and milesi (Lea 1863).  That brought our continental fauna down to 10.

Returning to the main key, on page 229, we find an earnest effort to distinguish, by shell morphology alone, eight species of Campeloma.  Three of the ten species surviving Burch’s endnote (4) did not survive the perilous transfer forward from page 268 to page 229.  The specific nomina brevispirum (Baker 1928), exilis (Anthony 1860), and gibba (Currier 1867) seem to have vanished [33].  But one brand new species of Campeloma was added, Vail’s [26] parthenum, bringing our total continental Campeloma fauna to N = 8 canonical species, as of 1982.  In the order of their description:

  • Limnaea decisa Say 1817.  Clench speculated “Delaware River?”
  • Campeloma crassula Rafinesque 1819.  The Ohio.
  • Paludina genicula Conrad 1834.  Flint River, GA.
  • Paludina regularis Lea 1841. Coosa R, AL.
  • Paludina lima Anthony 1860. South Carolina.
  • Melantho decampi Binney 1865. Decatur, AL. [34]
  • Campeloma floridense Call 1886.  Wekiva River, FL.
  • Campeloma parthenum Vail 1979.  Lake Talquin, FL.

The Burch/Vail key to the Campeloma begins with aperture color (white vs brown), then moves on to shell shoulders (angled vs rounded) then moves on to shell profile (broadly ovate vs narrowly ovate), and so forth.  It is a valiant effort, and I do not mean to diminish the contribution of its authors.  Just the opposite.

Science is the construction of testable hypotheses about the natural world.  It is not about being right, it is about being testable.  The Burch/Vail dichotomous key to distinguish the eight canonical species of North American Campeloma is science.

Next month, we test it.

Notes

[1] For my remembrance of J.P.E. Morrison, see:

  • Joe Morrison and the Great Pleurocera Controversy [10Nov10]

[2] For a bit more about Leslie Hubricht, see:

  • The Most Cryptic Freshwater Gastropod in the World [6Aug17]

[3] Most of the biographical details relayed above were gleaned from: Turner, R. D. (1985)  William J. Clench October 24, 1897 – February 22, 1984.  Malacological Review 18: 123-124.

[4] Surprisingly, Clench did not finish.  He was ultimately awarded honorary doctorates from both Michigan and MSU in 1953.

[5] Abbott RT (1984). "A Farewell to Bill Clench". The Nautilus 98 (2): 55–58.

[6] This is a detail from a scan of the original 8x10 glossy in my files.  The back is stamped, “Dept. of Photography & Cinema, The Ohio State University,  No. 191231-1, Please Give Credit”  Done.

[7] Clarke, A.H. (1981) The Freshwater Mollusks of Canada. Ottawa: The National Museums of Canada.

[8] Johnson, R.I. (2003)  Molluscan taxa and bibliographies of William James Clench and Ruth Dixon Turner.  Bulletin of the Museum of Comparative Zoology at Harvard College 158: 1- 46.

[9] Clench, W.J. & R.D. Turner (1956)  Freshwater mollusks of Alabama, Georgia, and Florida from the Escambia to the Suwannee River. Bull. Fla. State Mus. (Biol. Sci.), 1: 97-239.   For more, see:

  • Fred Thompson, Steve Chambers, and the pleurocerids of Florida [15Feb17]

[10] Clench, W.J. (1962) A catalogue of the Viviparidae of North America with notes on the distribution of Viviparus georgianus Lea. Occasional Papers on Mollusks 2(27): 261-287.

[11] Clench, W.J. & S.L.H. Fuller (1965) The genus Viviparus (Viviparidae) in North America. Occasional Papers on Mollusks 2(32): 385-412.

[12] Graf [13] has catalogued “nearly 1,000” specific nomina historically applied to North American freshwater gastropods of the family Pleuroceridae.  Between 1934 – 1944 my hero Cavin Goodrich was able to pare these down to approximately 150.  For more, see:

  • The Legacy of Calvin Goodrich [23Jan07]

[13] Graf, D. L. (2001) The cleansing of the Augean Stables, or a lexicon of the nominal species of the Pleuroceridae (Gastropoda: Prosobranchia) of recent North America, north of Mexico. Walkerana 12 (27) 1 - 124.

[14] For more about the “Nestor of American Naturalists,” see:

  • Isaac Lea Drives Me Nuts [5Nov19]

[15] For the further exploits of my hero, see:

  • Goodrichian Taxon Shift [20Feb07]
  • Mobile Basin II: Leptoxis Lessons [15Sept09]
  • CPP Diary: The Spurious Lithasia of Caney Fork [4Sept19]

[16] This is a difficult work to cite.  J. B. Burch's North American Freshwater Snails was published in three different ways.  It was initially commissioned as an identification manual by the US EPA and published by the agency in 1982.  It was also serially published in the journal Walkerana (1980, 1982, 1988) and finally as stand-alone volume in 1989 (Malacological Publications, Hamburg, MI).

[17] The parallel between the careers of Virginia Vail and George Te is inescapable here.  George Te was a Burch student in the late 1970s and seems to have ghost-written Burch’s entire treatment of the Physidae, as Virginia Vail ghost-wrote the Viviparidae.  For more on George Te, see:

  • To Identify a Physa, 1975 [6May14]
  • To Identify a Physa, 1978 [12June14]

[18] Abbott, R.T. (1975)  American Malacologists, Supplement.  American Malacologists, Greenville, Delaware. 

[19] Vail, V.A. (1977)  Comparative reproductive anatomy of 3 viviparid gastropods.  Malacologia 5: 519 – 540.

[20] Vail, V.A. (1978)  Seasonal reproductive patterns in 3 viviparid gastropods.  Malacologia 6: 73 – 97.

[21]  The viviparids have evolved [22] quite a few unique adaptations that separate them from all other living gastropods, including a weird operculum and even weirder radula.  The right tentacle of the male has been modified into a simple, external penis and the pallial gonoduct of the female modified into a marsupium, capable of nursing fertilized eggs until their hatch into impressively large crawl-away juveniles.  But within the family, their anatomy is as boringly uniform as the pleurocerids.  You crack a Viviparus shell, or a Lioplax shell, or a Campeloma shell, and look inside, and it’s basically viviparid guts.  Every time.

[22] “Retained” might be a better verb here.  The worldwide family Viviparidae seems to be ancient.  They share their peculiar concentric operculum with the Ampullaridae, which suggests that the two families are sisters.  But the viviparids have absolutely no living marine antecedents.  I take this as evidence of an hypothesis I advanced back in 2009, that evolution is slower in fresh waters than in the marine environments from which all life originated.  Like the pleurocerids, the viviparids are “living fossils.”  For more, see:

  • The snails the dinosaurs saw [16Mar09]

[23] Mattox, N.T. (1937) Oogenesis of Campeloma rufum, a partheogenetic snail.  Zeitschrift fur Zellforschung und Mikroskopische Anatomie 27: 455 – 464.

Mattox, N.T. (1938)  Morphology of Campeloma rufum, a parthenogenetic snail.  Journal of Morphology 62: 243-261.

[24] Mattox sampled his study population from a tributary of the Wabash River in eastern Illinois.  Clench [10] subsequently synonymized Campeloma rufum under C. crassulum (Raf.) 

[25] Abbreviations from Vail [19] figures 5 and 10: AG = albumin gland, CM = columellar muscle, DG = digestive gland, M = mantle, O = ovary, OD = oviduct, PMC = posterior end mantle cavity, PO = pallial oviduct, PR = prostate gland, RT = right tentacle, SR = seminal receptacle, SV = seminal vesicle, T = testis, V = vagina, VD = vas deferens,  VD’ = pallial vas deferens.

[26] Vail, V.A. (1979) Campeloma parthenum (Gastropoda: Viviparidae), a new species from north Florida.  Malac. Rev. 12:85-86. 

[27]  Isn’t it interesting the way we can remember small vignettes from 40 years ago, but cannot remember what we had for supper last night [28]?  Virginia Vail gave her talk in the freshwater session of the Corpus Christie AMU meeting at 11:00 Thursday morning, August 9, 1979.  Young Rob Dillon, then listed as a graduate student at the University of Pennsylvania, gave his talk at 11:15, “The Goniobasis of southern Virginia and northwestern North Carolina: Electrophoretic and shell morphological relationships [29].”  At approximately 11:31, Old Joe Morrison jumped up and lectured me with great passion about obscure details of pleurocerid taxonomy and systematics.  At about 11:35, I said, “Easy, big fella.”  For more, see:

  • Joe Morrison and The Great Pleurocera controversy [10Nov10]

[28] It was a chicken casserole, with cashews sprinkled on top.  I just looked in the refrigerator.

[29] That was just the second presentation I had ever made at a national meeting.  The research was ultimately published as: Dillon, R.T., Jr and G.M. Davis (1980) The Goniobasis of southern Virginia and northwestern North Carolina: Genetic and shell morphometric relationships. Malacologia 20: 83-98. [PDF]

[30] Thompson, F.G. (2000)  An identification manual for the freshwater snails of Florida.  Walkerana 10(23): 1 -96.  Also available online [html].

[31] No, it was not at an AMU meeting.  Jack Burch was never a member of the AMU/AMS during his entire professional career, as far as I know, until being elected an honorary life member in 2009.  His election was not unanimous.

[32] Clarke, A.H. (1973) The freshwater mollusks of the Canadian Interior Basin.  Malacologia 13: 1 – 509.

[33] The nomina brevispirum (Baker 1928), exilis (Anthony 1860), and gibba (Currier 1867) were not actually forgotten.  If you look forward into Burch’s “Species List, Ranges, and Illustrations” on page 92, you will find them synonymized under Campeloma decisum.

[34] “Huntsville or Stevenson, Alabama.”  This was corrected to Decatur, AL by: Clench, W. J. and R.D. Turner (1955) The North American genus Lioplax in the Family Viviparidae.  Occasional Papers on Mollusks, Museum of Comparative Zoology, Harvard. 2(19): 1 -  20.