Three New Fontigens From Virginia

Editor's Note - This essay was previously published as: Dillon, R. T., Jr. (2023b) Three new Fontigens from Virginia.  pp 225 - 232 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other Essays.  FWGNA Project, Charleston, SC.

The most faithful and attentive subset of my readership might perhaps remember an essay I posted a year ago this past August [9Aug22], wherein I reviewed the four-year journey that ultimately led to the confirmation of a Fontigens cryptica population inhabiting interstitial spaces in the karstland of central Kentucky [1].  Here is a detail that I cannot imagine any of you could possibly remember, no matter how attentive you have been.  About halfway through that essay I mentioned that two of the Fontigens samples Hsiu-Ping Liu sequenced for our big mtDNA gene tree were contributed by “our good friends Wil Orndorff and Tom Malabad of the VaDCR."

Lane Cave (F. hershleri)

Now let me highlight a blessing of the sort I have found gratifyingly common throughout my 40-year professional career, of which I should be more thankful, but which I fear I have often taken for granted.  Completely independent of the Fontigens cryptica research project that Lori Schroeder and I kept on a slow burner in Kentucky from 2017 – 2021, in November of 2018 I received a cordial email from my old friend Wil Orndorff [2], with the subject line “Some Virginia cave and spring snail collections that need you.”  And after a bit of negotiation, a big box containing 61 tiny plastic vials arrived with a thump on my front porch.  The even-tinier gastropod samples enclosed in those 61 tiny vials had been collected by VaDCR Natural Heritage from caves and cave springs all over the Old Dominion, 1998 – 2018.  Holy crap, I replied to Wil.  N=61 is not “some.”

A bit daunted, perhaps, but undeterred, I went to work sorting and identifying Wil’s very large sample of very tiny snails, a process that stretched four months, into March of 2019.  Of the 61 samples, 30 contained only land snails, and 11 contained only freshwater gastropods typical of above-ground habitats: pleurocerids, physids, and so forth.  That left a (still remarkable) 20 samples of hydrobioid cave snails on my lab bench.

Of all 7,999,999,999 people alive in this world today who have not pulled a fire alarm at the Academy of Natural Sciences of Philadelphia in the middle of the night [3], I flatter myself that I have developed the keenest eye for Fontigens.  Those 20 samples included 11 of F. orolibas, 3 of F. bottimeri, 2 of F. morrisoni, 2 Holsingeria, and 2 samples of hydrobioid cave snails unlike any I had ever seen before.

From the Sugar Run Cave System of Giles County, Virginia, (draining west into the New -> Ohio) I found a single sample of 14 individual Fontigens bearing strikingly ovoid shells – much more convex in their outline than any I had ever seen, bearing a depressed apex.  And from Lane Cave in Scott County, Virginia, (draining south into the Clinch -> Tennessee) I found a singleton hydrobioid snail that looked more like an Amnicola or a Lyogyrus than a Fontigens.  I left those two lots unidentified in the spreadsheet I sent to Wil on 1Mar19.  And here is how I closed my email: “After I die, if I’m reincarnated [4] as the second Bob Hershler, I’ll take another look at these.  Not before.”

So two months later, Lori Schroeder and Andrew Berry discovered one single putative F. cryptica living under a rock at a springhead in the Bernheim Forest of central Kentucky [3July2019].  And fight it though I most certainly had for years, I found myself in the Fontigens business.  I contacted Hsiu-Ping Liu out in Denver and prevailed over her to join Lori, Andrew and me in a grant proposal, then set out on that Fontigens-themed tour of the Great Valley of Virginia I described in my essay of last August [9Aug22], upon my return promptly posting my large sample of tiny snails off to Hsiu-Ping for sequencing.

And included among all those control samples of F. nickliniana and F. orolibas and F. morrisoni and F. bottimeri were, quoting now from my email to Hsiu-Ping of 17July19 …

…two extra samples at the bottom of my spreadsheet, labelled “xtr1” and “xtr2.”  I think I told you that Wil Orndorff and our colleagues at the Va-DCR sent me a big shipment of cave snails last fall, from all over Virginia.  Included in that shipment were two samples I absolutely could not identify, one from Sugar Run Cave in Giles County, the other from Lane Cave in Scott County.  Obviously, these are very low priority.  But if, in the (increasingly unlikely) event we had a bit of money left over… my colleagues and I would be most gratified.

The first results came back from Hsiu-Ping in late August of 2019 – an early version of that gene tree I shared with you all on [9Aug22].  And we were immediately impressed by the tremendous interpopulation CO1 sequence divergence within our control species which, you will recall, ended up being the headline of the paper we ultimately published in 2021 [1].  But the intraspecific variance did not swamp out the sequence variation among species, which ranged from a bit less than 9% up to a bit more than 20%.  And the mean sequence divergence between three snails sampled from the Sugar Run Cave System and their nearest genetic neighbor (F. morrisoni) was 9.0%, and that between our singleton from Lane Cave and its nearest neighbor (one of the F. nickliniana populations) was 13.2%, strongly supporting the specific status of both those “xtr” populations.

Sugar Run Cave (F. benfieldi)

Again, I must emphasize.  I would never dream of looking for new species on a gene tree.  But I brought a hypothesis with me to the analysis that Hsiu-Ping so ably executed in August of 2019, arising from my understanding of the biology of the organisms I was studying.  I predicted that the Lane Cave and Sugar Run populations might represent heretofore undiscovered species of Fontigens.  And testing that hypothesis with a gene tree, I found that it was supported.

And so, I surrendered to the inevitability that I myself would be duty-bound to describe a couple new species of Fontigens in this life, rather than the next.  So, on 29Aug19 I wrote to Wil & Tom:

“Do you have any plans to return to either Lane Cave or Sugar Run Cave any time soon?  We really need more snails.  If you could find a decent sample size (I would love N = 30) I myself would be game to dissect them and describe them formally.  I’m not Bob Hershler, so need a bunch of extras, so I can screw up.  Species descriptions are not my forte, but it needs to be done, and I don’t know anybody else who could do it.”

The answer turned out to be an enthusiastic yes.  It materialized that over the previous nine months, Wil and Tom had continued to stomp all over the Commonwealth, lowering themselves upside down into every hole large enough to lose a basketball, scouring the inner recesses of the Old Dominion for Fontigens.  Although they had not revisited either Lane Cave or the Sugar Run Cave System by that point, they had already collected 12 fresh samples, which they were pleased to send me in September of 2019.  And in February of 2020, yet another fresh batch of 10 Fontigens samples arrived on my doorstep, this one including N = 3 from Lane Cave, N = 18 from the Sugar Run Cave System, and N = 39 from a new sampling location, Dulaney’s Cave, which turned out to be the most interesting of all.

At this point, a boxed essay on the environments from which these populations were sampled might be helpful.  Lane Cave is developed in Cambrian Marysville Limestone atop a bluff running parallel to Copper Creek of the Clinch River drainage, a tributary of the Tennessee.  The cave is a not-insubstantial 0.8 km long and about 60 m deep.  The stream running through it seems to be fed by multiple, small surface sinks at the top of the bluff, and apparently resurges at a spring tributary to Copper Creek.

The Sugar Run Cave system, 170 km northeast, is much larger and more complicated. Developed 200 m deep in Ordovician limestone on the northeast flank of Sugar Run Mountain, the system includes at least 45 km of passages, multiple streams and multiple entrances, the relationships among which are poorly understood.  The sample that Tom & Wil sent me in February labeled “Dulaneys Cave” came from waters connected to subterranean Sugar Run through some unknown passage, all of which ultimately drains into Walker Creek of the New (-> Ohio) River system.

Dulaney's Cave, elongate (F. davisi)

And when I dumped that little plastic vial labeled “Dulaneys” into a dish under my dissecting scope, my eyes were met by quite the unexpected sight.

Yes, I counted N = 31 of those strange Fontigens bearing the unique ovoid shells I had previously seen in the Sugar Run samples.  But plopped right in the middle of those 31 were N = 8 individuals of what looked like yet another species of Fontigens – a third one – I had never seen before.  These bore shells that were larger, and darker, and elongate/pupoid in overall outline.  Good grief!

So I started my dissections.  And of course, after each dissection I saved all the tissues for sequencing.  And in March of 2020 I pitched Hsiu-Ping on the possibility of a second project, beyond the Fontigens cryptica project to which we were already obligated, describing three new Fontigens species from Virginia.

Well, by that point pretty much all the college campuses nationwide were in the grip of the Coronavirus panic.  But Hsiu-Ping, bless her heart, moved her lab into the basement of her private home, and with perhaps even less distraction than she might have otherwise suffered in an ordinary spring semester, was happy to collaborate. 

And in so in May of 2020 I sent Hsiu-Ping two fresh samples of the Lane Cave unknown, three from Sugar Run, and three from Dulaney Cave.  I told her that the Dulaney sample looked like two different shell phenotypes to me, elongate and ovoid, although I didn’t tell her which tubes held which phenotype.  And by that point I was aware of the anatomical similarity between the Dulaney/Sugar Run snails and Fontigens orolibas.  So I also sent her a fresh control sample of F. orolibas from nearby Tawney’s Cave [5] as well.

Baysian Tree abbreviated from [6]

The CO1 gene tree above is an abridged version of the tree Hsiu-Ping sent me in March of 2021, showing just one individual per population.  The full-featured model, which you can see in the Appendix of Volume 5 [6], was based on N = 47 individual Fontigens, including 3 individuals from Lane Cave, 6 from Sugar Run, 2 Dulaneys-elongate, 1 Dulaneys-ovoid, and 2 from the control orolibas at Tawney’s Cave.  Most of the data (shown in black) were borrowed from the F. cryptica study of Liu et al [1] published in 2021.  The sequences in blue are new.

Marked in red are the minimum sequence divergences between each of our three putatively new species and its nearest neighbor, all greater than the minimum intraspecific distance we set in our 2021 paper.

The bottom line was just published last month as an appendix to FWGNA Volume 5, by Dillon, Malabad, Orndorff and Liu [6].  The two new Fontigens species from the Sugar Run / Dulaney system are both members of the orolibas group, bearing a tripartite penis with one tubular and one bulbous accessory gland.  The bodies and eyespots of both species are unpigmented.  I was pleased to name the population bearing ovoid shells for Dr. Ernest F. (Fred) Benfield, my undergraduate mentor at Virginia Tech [7], and the population bearing elongate shells for Dr. George M. Davis, my graduate mentor at the ANSP [8].

The Lane Cave Fontigens is a member of the nickliniana group, its tripartite penis bearing two tubular glands.  Its body and eye spots are pigmented.  These observations, together with the fact that our collections arrived in a mixture with juvenile above-ground-dwelling Pleurocera simplex (Say), suggest to us that the Lane Cave Fontigens might be capable of living in surface waters.  This new species I was gratified to name in honor of my buddy, Bob [3].

 

Notes:

[1] Liu, H-P., L. Schroeder, A. Berry, and R.T. Dillon, Jr. (2021) High levels of mitochondrial DNA sequence divergence among isolated populations of Fontigens (Truncatelloidea: Emmericiidae) in eastern USA. Journal of Molluscan Studies 87. [pdf] [html]

[2] You might remember Wil as the leader of that expedition I undertook into Unthanks Cave way back in 2007, as described in:

• Cave Snail Adventure [12Aug07]

[3] For a review of the professional contributions of Dr. Robert Hershler, together with a well-curated anecdote or two more personal in their nature, see:

• My Buddy Bob [6July22]

[4] To be very clear, I am a Presbyterian.  If I find myself reincarnated as anything – be it cow, bug, malacologist or Methodist – I shall be most disappointed.

[5] Two of our previous [1] orolibas populations (including the topotypes) came from Atlantic drainages, and the third was from a Tennessee drainage.  So since the Sugar Run Cave system drains toward the New River, we felt as though a fourth orolibas control (Tawney’s Cave) was necessary.

[6] Dillon, R.T., Jr., T.E. Malabad, W.D. Orndorff & H-P. Liu (2023) Three new Fontigens (Caenogastropoda: Fontigentidae) from caves in the Appalachian Ridge and Valley Province, Virginia. Pp. 283 - 306 in Dillon, R.T., Jr. et al. The Freshwater Gastropods of North America Volume V: Ohio, Cumberland, and Tennessee River Systems. FWGNA Press, Charleston. [pdf]  Order your copies today!

• FWGNA Volumes 5, 6, and 7 Now Available! [6Dec23]

[7] Fred Benfield made cameo appearances in my essay of 6Apr23 (Growing Up With Periwinkles) and in my essay of [6May14], (To Identify a Physa, 1975).  Look at footnote #16 of the 2014 essay for a sample of Fred's memorable advice.

[8] George Davis costarred with Steve Ahlstedt in my essay of 5Apr22 (The Ham, the Cheese, and Lithasia jayana) and made cameo appearances in [28Mar22], [11Mar19], and [16July10].

FWGNA Volumes 5, 6, and 7 Now Available!

It is our great pleasure to announce the publication of Volumes 5, 6, and 7 in the Freshwater Gastropods of North America series, now extending FWGNA coverage from U.S. Atlantic drainages into the Ohio, Cumberland and Tennessee River systems of the American interior.  These three important new references, essential for the libraries of malacologists, aquatic biologists and natural resource managers with interests anywhere in the East, are now available at a substantial discount directly from the print shop, only to friends of the FWGNA Project.

FWGNA Volume 5, by Dillon, Kohl, Winters, Pyron, Reeves, Watters, Cummings, Bailey and Whitman [1], reports the scientific results of a freshwater gastropod survey covering all or part of 14 U.S. states, a total study area of over 200,000 square miles.  Our database of 9,370 records, sampled from approximately 4,250 distinct sites, was drawn from museums (24%), state natural resource agencies (34%), and personal collections.

We document 80 species and 19 subspecies of freshwater gastropods in this malacologically rich region.  For each we provide: 

• A dichotomous key for identification. 
• Full-color figures. 
• Range maps at county scale. 
• Notes on habitat, ecology, life history and reproductive biology. 
• Systematic and taxonomic updates to modern standards.

Three new species of cave-dwelling hydrobioid snails: Fontigens hershleri, F. benfieldi, and F. davisi, are described in the appendix [2].

Our complete FWGNA database, updating Atlantic drainage records and combining them with our fresh data from the interior, now comprises 22,044 records documenting 107 species of freshwater gastropods, with 21 subspecies.  In Volume 5 we offer a new continent-scale biogeographic analysis, dividing records into North Atlantic, South Atlantic, Ohio, and Tennessee/Cumberland subsets.  Our analysis suggests that natural selection has been more important in the evolution of freshwater pulmonate snails than gene flow restriction, but that gene flow restriction has been more important in the evolution of freshwater prosobranch snails than natural selection.

In Volume 1 (2019) we pioneered a new method to rank freshwater gastropods by incidence categories for the purposes of conservation, based on the work of K. J. Gaston.  Here in Volume 5 that system is updated to include all 107 species across all regions, re-assigning incidence ranks as necessary.

Our modern understanding of the taxonomy and systematics of the North American freshwater gastropod fauna is a function of both the natural history of the vast rivers, lakes and streams through which that diverse fauna has evolved, and the human history of the biologists who have come behind, struggling to catalog the biodiversity as it has elaborated before their eyes.  In FWGNA Volume 6 [3] we collect 32 essays, originally published on the present blog 2019 – 2023, exploring the relationship between natural history, human history, and the evolutionary models we impose today upon the pleurocerid snails of the American interior, and upon the hydrobioid snails, broadly understood.

Featured topics include intrapopulation gene flow, barriers to dispersal, character phase disequilibrium, and speciation.  Special attention is called to the phenomena of cryptic phenotypic plasticity and mitochondrial superheterogeneity, both of which were introduced in Volume 3 of the present series (2019).  Along the way we meet Professor Gerard Troost, who was twice-captured and ransomed by privateers, Captain S. S. Lyon, who singlehandedly saved the Union command of George W. Morgan in 1862, and Dr. Isaac Lea, the Nestor of American Naturalists, who drives us nuts.  Together these 32 studies comprise an essential companion to the scientific results of the 14-state survey of the freshwater gastropod fauna The Ohio, Cumberland, and Tennessee River systems published in Volume 5.

And what is the place of freshwater snails in modern culture, if any?  Does their alleged rarity and undeniable strangeness elicit conservation concern in small circles of the environmentally conscious?  Might even smaller circles of professionals in tropical medicine and health worry about their potential to host parasitic diseases?  And aren’t some freshwater snails invasive?  Or maybe they’re just cute pets?

Collected in FWGNA Volume 7 [4] are 36 essays, originally published in the genre-defining artistic universe known as the FWGNA Blog, exploring freshwater gastropod biology in the modern milieu.  Our focus here is on the larger prosobranchs – the viviparids and the ampullariid “mystery snails” – as well as on the familiar pulmonate snails of the hobbyist aquarium and the lab bench. 

Reproductive allocation and the species concept, especially as applied to asexually-reproducing populations, emerge as primary themes, together with the omnipresent phenomenon of phenotypic plasticity.  And along the way we’ll check in with Gary, a pet mystery snail, who doesn’t smell so good.  The essays collected here will be an essential companion both to the Volume 1 results of the FWGNA surveys of Atlantic drainages published in 2019, and to the results of the Volume 5 Ohio drainage surveys published alongside.

Buy Yours Now!

The retail price of these three indispensable volumes, if purchased separately, would be $56.00 + $48.89 + $53.79 = $158.68.  But we have worked out a special deal with the print shop for friends of the FWGNA Project.  Go directly to my author page on the printer’s website, link above.  Add each of the three new titles [5] separately to your cart and proceed to checkout.  At the checkout page you will find a box to enter a “coupon code.”  Apply the coupon code FWGNA3 to each of the three volumes.  This will discount your price to $99.95 for the set.  A bargain!

Notes

[1] Dillon, R.T. Jr., M. Kohl, R. Winters, M. Pyron, W.K. Reeves, G.T. Watters, K. Cummings, J. Bailey, & M. Whitman (2023a) Ohio, Cumberland, and Tennessee River Systems.  Freshwater Gastropods of North America, Volume 5.  FWGNA Press, Charleston, SC. 315 pp.

[2] Dillon, R.T., Jr., T.E. Malabad, W.D. Orndorff & H-P. Liu (2023) Three new Fontigens (Caenogastropoda: Fontigentidae) from caves in the Appalachian Ridge and Valley Province, Virginia. Pp. 283 - 306 in Dillon, R.T., Jr. et al. The Freshwater Gastropods of North America Volume V: Ohio, Cumberland, and Tennessee River Systems. FWGNA Press, Charleston. [pdf]

[3] Dillon, R.T., Jr. (2023b) Yankees at The Gap, and Other Essays. Freshwater Gastropods of North America Volume 6.  FWGNA Press, Charleston, SC.  306 pp.

[4] Dillon, R.T., Jr. (2023c)  Collected in Turn One, and Other Essays.  Freshwater Gastropods of North America Volume 7.  FWGNA Press, Charleston, SC. 345 pp.

[5] Oh, and the special deal we worked out for Volumes 1 – 4 back in 2019 is still valid.  If you follow the entire procedure outlined above for Volumes 1 – 4 and add the coupon code FWGNA4, you will receive a discounted price of $99.95 for that set as well.

Atlantic Drainages Update

Our hunger to advance the cause of freshwater gastropod science is insatiable here at the general headquarters of the FWGNA Project.  I’m always scanning the literature for the latest research and looking to add new records to the database, even for those regions we covered and published many years ago, from which we seem to have long moved on.  We haven’t “moved on” from anywhere.  Our coverage extends over all or part of 17 states, expanding south and west, active to the present day.

But it has been ten years – if you can believe it – since we last updated the five web resources that cover the freshwater gastropod fauna of U.S. Atlantic drainages:  Georgia (FWGGA), South Carolina (FWGSC), North Carolina (FWGNC), Virginia (FWGVA) and the Mid-Atlantic (FWGMA).

Fresh 2023 Format

So a couple months ago we were able to twist the arm of our good friend Martin Kohl to help us with a fresh set of maps, which is the biggest piece of the chore.  And today we are pleased to announce that the results of Martin’s considerable GIS skills are now available for download from the pages of the 72 species and subspecies of gastropods inhabiting rivers, lakes, ponds and streams of the vast (ten-state) Atlantic-drainage area.

The maps newly available for 2023 are built on a database of 12,138 records.  That number represents a 4.2% reduction from the 12,674 Atlantic-drainage records upon which we based our (most recent) Synthesis v3.1 and Biogeography v2.0 back on 12May22.  The new total reflects a pruning of our FWGNC database from 4,425 down to 3,809 records to remove a big batch of near-duplicate samples, collected by NCWRC teams upstream and downstream from bridges, for example.

Other FWGNA Atlantic-drainage databases have been slightly augmented by routine collecting, however, up from 895 to 960 in Georgia, from 1,938 to 1,989 in South Carolina, from 2,333 to 2,396 in Virginia, and from 3,150 to 3,159 in the Mid-Atlantic states.  Note that the sum of those five figures totals slightly more than 12,138 due to double counting where rivers comprise state lines.

Our 2013 maps emphasized rivers, streams, and vegetative cover.  Our new 2023 maps have been significantly reformatted to show the major USGS/EPA Ecoregions, with counties and cities (very lightly) in the background.  Close comparison of the two examples (above and below) will reveal a slight reduction in data density for North Carolina, and some fresh data mapped, especially in Georgia.

Old 2013 Format

The contents of all 128 species pages on the FWGNA site have also been refreshed in recent months – not just the 72 species and subspecies of Atlantic drainages.  I am always on the lookout for new research to add to the bibliographies – ecology, life history, systematics, evolution – anything and everything, really.

Whenever any of you publish anything new, please send me a link or a reprint.  Indeed, if you happen to read a new paper with especially interesting or important results on any aspect of the biology of North American freshwater gastropods, written by anybody else, I always appreciate a heads-up.

For many years, my customary sign-off has been, “Keep in touch.”  I mean it, I’m serious!

Deadly Snails Invading the US!

Yesterday evening my wife and I were having supper with family friends when a young lady – very much attuned to social media of diverse sorts, as so many of the youth these days – mentioned that she had been “bombarded” with alerts about dangerous snails in North Carolina.  This was completely out of the blue.  She’s not a biologist – does not follow technical news feeds – just a regular citizen of the Charleston area in her mid-20s.

NCWRC

I, very much the opposite, confessed complete ignorance of the situation.  So, our young friend whipped out her smart phone, deftly touched off three key strokes and a swipe, and there was the news.  Invasive Pomacea of the maculata/canaliculata sort have been reported in the Lumber River at Lumberton, NC.  But my goodness, the hysteria!

The media frenzy seems to have been kicked off by a perfectly responsible press release from the North Carolina Wildlife Resources Commission on Monday 2Oct23 [1].  Initially alerted by a concerned citizen, the NCWRC conducted a survey that did indeed confirm an invasive Pomacea population extending from the I-95 bridge just above Lumberton [2] to a boat ramp about 6 km downstream.  In measured tones, the press release cautioned:

“Apple Snail grazing habits can damage plants used by many native aquatic species and they have even been observed feeding on amphibian eggs. Additionally, Apple Snails can present human health risks. They may carry rat lungworm, which can cause a potentially fatal disease in humans if the snails are eaten raw or undercooked.”

From that relatively innocuous paragraph came the New York Post headline of 4Oct23, “Deadly Apple Snails found along North Carolina River,” and from CBS News, “Invasive snails that can be deadly to humans found in North Carolina.”  But my favourite headline came from the UK Daily Mail, “Invasive Snails Deadly to Humans are Invading the US!” [html] [pdf] 

The Lumber River continues into South Carolina to unite with the PeeDee River about 50 km downstream from Lumberton.  Another 80 km downstream by kayak through impenetrable swamp would bring us to the mouth of the Waccamaw River, from whence it is but 10 – 15 km back upstream to Socastee, SC, where invasive Pomacea were first reported in 2008 [3].  Whether the North Carolina population represents a new introduction, or simply a 150 km expansion of the South Carolina population, remains to be determined.

We saw a similar wave of concern spread through the Myrtle Beach area of South Carolina when the snails first arrived here 15 years ago, although much lower in amplitude and local in extent.  The local newspapers here described apple snails as merely “harmful” or “worrisome,” not “deadly.”

In retrospect, the NCWRC might have added significantly more context to their press release.  South Carolina researchers have found no evidence of Angiostrongylus parasitism in samples of Pomacea taken here in The Palmetto State [4].  Indeed, the extensive 2013 survey conducted by Teem and colleagues across Louisiana, Texas, Mississippi, and Florida yielded only 8 cases of Angiostrongylus parasitism in 296 Pomacea tested, all from the New Orleans area [5].  And as for cases of actual rat lungworm disease in humans, the CDC was only able to confirm 12 cases in the continental USA 2011 - 2017, the majority of which were linked to eating raw vegetables, not snails [6].

So when invasive Pomacea arrive in Virginia, here’s a suggestion for that press release.  Bold the clause, “if the snails are eaten.”  And suggest that the readership resist the temptation to pop one in their mouths.  Everything will be OK.

Notes

[1] Invasive Apple Snails Now Confirmed in North Carolina.  North Carolina Wildlife Resources Commission, 2October23. [html] [pdf]

[2] In my blog post of 13June18, I advocated legislation to build “a big, beautiful wall on the North Carolina line from Cape Hatteras to Tennessee, 50 feet tall by back-of-the-envelope calculation, Pedro himself manning the I-95 guardhouse just two mucus trails and one gigantic traffic jam North of the Border” to intercept just such a Pomacea invasion as North Carolina is now experiencing here in 2023.  See, I told you so.

[3] More about Pomacea in South Carolina:

• Pomacea spreads to South Carolina [15May08]
• Two dispatches from the Pomacea front [14Aug08]
• Pomacea News [25July13]
• Invasive species updates [13June18]

[4] Underwood, E.B., M.J. Walker, T.L. Darden & P.R. Kingsley-Smith (2019) Frequency of occurrence of the rat lungworm parasite in the invasive island apple snail in South Carolina, USA.  Journal of Aquatic Animal Health 31(2): 168 – 172.

[5] Teem, J.L., Y. Qvarnstrom, H.S. Bishop, A.J. DaSilva, J. Carter, J. White-Mclean, and T. Smith (2013)  The occurrence of the rat lungworm, Angiostrongylus cantonensis, in nonindigenous snails in the Gulf of Mexico region of the United States.  Hawaii J. Med. Publ. Health 72: 11 – 14.

[6] Liu EW, Schwartz BS, Hysmith ND, et al. (2018) Rat Lungworm Infection Associated with Central Nervous System Disease — Eight U.S. States, January 2011–January 2017. Morb Mortal Wkly Rep 67:825–828.

Is Marstonia olivacea extinct?

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023b)  Malacological mysteries: Is Marstonia olivacea extinct?  Pp 269 – 278 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other Essays.  FWGNA Project, Charleston, SC.

Questions regarding the habitat and range of the hydrobiid snail known today as Marstonia olivacea have always taken precedence over any other aspect of its biology.  Originally described in the genus Amnicola by Henry Pilsbry in the February 1895 issue of The Nautilus [1], the name had already appeared in that journal twice previously – first in March of 1894 [2], then again in December [3].

Both anticipatory articles were contributed by Prof. H.E. Sargent of Woodville, AL, and both focused on habitat.  In the March article, “Shell collecting in Northern Alabama,” Professor Sargent observed:

“Huntsville, Alabama, is a somewhat exceptional southern city in that it has an abundant supply of pure spring water bursting forth from its very foundations.  This spring of sparkling lime water, beside supplying the city mains, affords a constant stream several feet in width with several inches in depth go to waste. […] The upper surfaces of the rocks were found to be covered with a species of Amnicola which the Editor … proposes the name of Amnicola olivacea Pils.”

And in a little “Notes and News” item tacked onto the end of the December 1894 issue of The Nautilus, the good professor added,

“AMNICOLA OLIVACEA PILS. – In  April, I visited the original locality (Huntsville, Ala.) and was surprised to find this species in vast numbers.  The stream has a mud bottom which is much indented with cow tracks.  In these the Amnicola had congregated – not as a layer on the surface, but as a solid mass. […] The stream receives some of the city sewerage, so it is probably a good feeding-ground.”

Prof. Sargent’s December remark about “sewerage” in Huntsville’s Big Spring Creek is telling.  We ourselves first visited that unfortunate little body of water in our essay of [15Apr20], questing for Isaac Lea’s Melania perstriata, and gave it another nod in last month’s essay [15Aug23], searching for the illusive Somatogyrus currierianus.  The last time I visited that “marvel to Indian and frontiersmen alike,” I couldn’t even find a Physa.  I have nevertheless marked the Huntsville Big Spring as HV on the map below.

But returning to the thread of our story.  Henry Pilsbry did not apparently find space to wedge his formal description of Amnicola olivacea until the fifth article of the issue he published in February 1895.  And when it appeared it was maddeningly brief and spare, unfigured, and absent any anatomical observations whatsoever [4].  The two shells that he measured were unusually large by hydrobiid standards, however, both “Alt 4.2 mm,” and slender “being of more elongated contour than any other Northern forms except Amnicola lustrica.”  Those observations plus the type locality (“Huntsville, Ala., collected by Prof. H. E. Sargent”) were sufficient to allow subsequent authors to establish the identity of Pilsbry’s taxon.

The first among those subsequent authors seems to have been my hero Calvin Goodrich [5], who wrote in 1944, “This species is somewhat common in streams and springs in and around Huntsville, Madison County, Alabama, drained by the Tennessee River.  Specimens taken by Smith in the Coosa, Minnesota Bend, Etowah County, Alabama [6], have been identified as olivacea.”  This strongly implies that Goodrich was aware of populations of Pilsbry’s A. olivacea at other localities beyond Huntsville’s Big Spring.  The four lots of Marstonia olivacea held in the UMMZ collection today, however, all give locality as either “Huntsville” or “Huntsville Spring” [7].

M. olivacea [12]: lectotype, Hershler, UF279638

But Goodrich was a pleurocerid guy, not a hydrobiid guy.  It was Fred Thompson who first stepped forward to examine Pilsbry’s Amnicola olivacea with a critical eye, in his landmark monograph of 1977 [8].  As my longsuffering readership will remember from last fall [4Oct22], it was Thompson who first elevated F. C. Baker’s [9] nomen Marstonia to the level of a full genus, recognizing as he did eight species in it: Pilsbry’s well-known lustrica, Pilsbry’s obscure olivacea, and six species of his own.

Thompson wrote, “Apparently this species (M. olivacea) was confined to Big Spring Creek in the historic heart of Huntsville.”  And he continued, “This snail is probably extinct.  The creek is badly polluted and has been channelized for most of its course.  No specimens were found by the author during two visits to Big Spring Creek during 1973.”  He went on to examine the paratype lot (N = 456 specimens!) in the ANSP, valiantly attempting “to extract and relax dried bodies,” failing.  He selected the shell figured above as a lectotype.  And regarding its morphology, Thompson observed, “If M. olivacea was from a more northern locality, I would be tempted to consider it a synonym of the highly variable M. lustrica.”  He concluded, “This species’ status remains uncertain.”

My longsuffering readership will also remember from last fall [4Oct22] that Marstonia was briefly synonymized under the genus Pyrgulopsis in 1987 by the dynamic duo of Hershler and Thompson, only to be resurrected again in 2002 [10].  In the interim was published Bob Hershler’s masterful 1994 monograph [11] treating Pilsbry’s olivacea as an “Eastern American Species” in the (temporarily very large) genus Pyrgulopsis.

My Buddy Bob’s scanning electron micrograph of the shell of a young “Pyrgulopsis” olivacea [12] is reproduced middle above.  Bob was also apparently able to rehydrate soft tissues from inside some of Pilsbry’s dried shells, contributing a figure of the radula and a four-line description of the penial morphology.  Hershler left the penis unfigured, alas, and only compared it to other species in broad outline [13].  He concluded, briefly, “This snail resembles widely disjunct P. lustrica in shape of shell and penis, but differs in having strong spiral lines on the teleoconch.”

Hershler quoted Thompson’s understanding of the distribution of P. olivacea, minus any qualification whatsoever, “Known only from type locality, where it is now extinct.”  And that would seem to be the end of this month’s lesson.  Perhaps class will be dismissed early today?  No such luck.

The Florida Museum of Natural History in Gainesville is a marvelous facility, home to a large and well-curated collection extending well beyond regional importance.  The review I posted on [22May19] ranked the FLMNH as #5 in the nation by its freshwater gastropod holdings.  I’d like to call it a beacon on a hill, a guidepost toward which other states and state universities might sail.  But alas, the tide has turned, and the winds have blown ill for a hundred years.  We malacologists of these latter days must give thanks for the few scattered beacons we have, as we strain to navigate by their flickering lights.

So it was that on Monday morning, 10Jan22 I found myself sitting at a metal table in the FLMNH collections, running my fingers through Fred Thompson’s hydrobioid collections from North Alabama, pondering weak and weary, over many a quaint and curious lot of freshwater gastropods.  And my eye happened to fall on lot UF279638, collected by FGT from “Madison Co: Huntsville Blue Springs” (site BA) on 17Aug2000 [14].  That lot of dry shells, indistinguishable to my eye from common Marstonia lustrica, collected from a large spring on private property 5 miles East of Huntsville, had been identified by Fred Thompson himself as Marstonia olivacea.  Marstonia olivacea is not extinct.

And that was not the last, nor the greatest revelation of the morning.  The FLMNH collection also held, upon further inspection, a lot UF279620, collected by FGT from Limestone Creek, about 20 miles west of Huntsville, on 16Aug2000, the previous day.  See map point LC above [15].  That lot, comprising a couple dozen specimens in 75% ethanol, was curated into the collection as “Pyrgulopsis n. sp.”  They were absolutely indistinguishable from lot UF279638.

UF279620, from Site LC

If Marstonia olivacea ranges 5 miles East of Huntsville, and 20 miles West of Huntsville, might it also range 60 miles East of Huntsville?  Begging the indulgence of my readership, allow me to step back 46 years, and eight paragraphs, and get a fresh start into this entire story.

Fred Thompson recognized eight species in his newly elevated genus Marstonia in 1977: lustrica, olivacea, agarhecta (which he himself had described in 1969) and five brand new ones.  On page 123 of his monograph, he opined that M. olivacea was endemic to Huntsville and probably extinct.  But two pages earlier he had newly described Marstonia ogmorhaphe [16] from Owen Springs, just over the Tennessee line 60 miles NE of Huntsville (map OS).  It was initially “known only from its type locality,” but a second population of M. ogmorhaphe was subsequently discovered 5 miles west, in the Blue Spring [17] of Marion County (map BT).

Thompson made no effort to distinguish his new M. ogmorhaphe from the older M. olivacea.  Quoting him verbatim from page 120, “Marstonia ogmorhaphe is distinguished from all other species of Marstonia by (1) its large size (4 – 5 mm), and (2) its large number of whorls (5.2 – 5.8).”  On page 123, Thompson went on to give the length of the holotype of M. olivacea as 4.35 mm, and number of whorls as 5.4.

Owen Springs, courtesy of Alan Cressler

Seventeen years later came Bob Hershler’s big Pyrgulopsis monograph [11], and the formal listing of Pyrgulopsis (= Marstonia) ogmorhaphe as “endangered” by the US Fish and Wildlife Service [18].  My buddy Bob’s treatment of this suddenly noble gastropod, now styled the “Royal Snail,” was brief.  Both he and Thompson noted the similarity between olivacea and lustrica, and both he and Thompson noted the similarity between ogmorhaphe and lustrica, but neither he nor Thompson thought to compare olivacea to ogmorhaphe.

So, in summary.  My biological intuition suggests to me that Marstonia ogmorhaphe (Thompson 1977) is a junior synonym of Marstonia olivacea (Pilsbry 1895).  The dispersal capabilities of freshwater gastropods are much greater, and their specific ranges much wider than they are commonly given credit for, even among professionals.  The (effectively indistinguishable) Marstonia lustrica ranges across 12 states and 3 Canadian provinces and must have spread across most of this vast territory since the Pleistocene [19].  I cannot see why populations of a second very similar species, best identified as Marstonia olivacea, could not spread 60 miles from North Alabama to East Tennessee.  And I cannot find a single speck of evidence suggesting that any reproductive isolation may have evolved subsequently.

Notes

[1] Pilsbry, H.A. (1895) New American fresh-water mollusks.  Nautilus 8: 114 – 116.

[2] Sargent, H.E. (1894) Shell collecting in Northern Alabama.  Nautilus 7: 121 – 122.

[3] Sargent, H.E. (1894) Amnicola olivacea Pils.  Nautilus 8: 95 – 96.

[4] My faithful readership will be familiar with the eccentricities of the character of The Ancient Emperor, Dr. Henry A. Pilsbry.  In his capacities as Curator of Mollusks at The Academy of Natural Sciences of Philadelphia and Editor of The Nautilus, he cast a giant shadow across the face of American malacology for 70 years.  You are also aware that Pilsbry was simultaneously fastidious and sloppy, capable of precise, detailed, and critical observations of parrot feathers in a pirate attack.  For more, see:

• The Emperor Speaks [5Dec20]
• The Emperor, the Non-child, and the Not-short-duct [9Feb21]
• Dr. Henry A. Pilsbry was a Jackass [26Jan21].

[5] Goodrich, C. (1944) Certain operculates of the Coosa River.  Nautilus 58: 1 – 10.

[6] The “specimens taken by Smith in the Coosa” were described as Marstonia hershleri by

• Thompson, F. G. (1995) A new freshwater snail from the Coosa River, Alabama (Gastropoda: Prosobranchia: Hydrobiidae).  Proc. Biol. Soc. Washington 108: 502 – 507.

[7] All of these lots are undated, alas.  They are catalogue numbers 120720 of H.E. Sargent, 143685 of H.H. Smith, 237147 of P.L. Marsh, and 1516 of an unknown collector.

[8] Thompson, F.G. (1977) The hydrobiid snail genus Marstonia.  Bulletin of the Florida State Museum 21(3):113-158.

[9] Baker, F. C. (1926) Nomenclatural notes on American fresh water Mollusca. Transactions of the Wisconsin Academy of Sciences, Arts, and Letters 22:193-205.

[10] Thompson, F. G. & R. Hershler (2002)  Two genera of North American freshwater snails: Marstonia Baker, 1926, resurrected to generic status, and Floridobia, new genus (Prosobranchia: Hydrobiidae: Nymphophilinae).  The Veliger 45: 269 - 271.

[11] Hershler, R. (1994)  A review of the North American freshwater snail genus Pyrgulopsis (Hydrobiidae).  Smithsonian Contributions to Zoology 554: 1 - 115.

[12] The standard lengths of these three figured shells are 4.3 mm for Thompson’s [8] lectotype, 4.5 mm for my selection from lot UF279638, and just 3.4 mm for Hershler’s [11] youngish specimen.  My Buddy Bob had a longtime romance with scanning electron microscopy, and tended to select smaller shells for his figures, which are easier.

[13] In fairness to Bob Hershler, the morphology of dried and rehydrated soft tissues cannot be compared to anything other than other dried and rehydrated soft tissues.  I would have loved to see a comparison of the penial morphology of M. olivacea, M. lustrica and M. ogmorhaphe, but to do so Bob would have had to desiccate a bunch of fresh lustrica or ogmorhaphe to brittle dryness first.

[14] There is an error in the lat/long coordinates for UF279638 as entered into the FLMNH database, which may have contributed to the obscurity of this record.  The correct lat/long coordinates for the Blue Spring of Madison County, Alabama, are 34.7080, -86.5123.  They are not “31.66361, -85.50667.”  Those are the coordinates of the Blue Springs of Barbour County, AL.

[15] This spot is way downstream near the mouth of Limestone Creek, underneath the I-565 spur, at 34.6317, -86.8667.

[16] Thompson spelled his new species “ogmorphaphe” at the heading of his description  and “ogmorhapha” in his table of contents, but “ogmorhaphe” enough times otherwise to make the one-pee-final-e spelling stick.

[17]  To be very clear.  The Blue Spring of Marion County, Tennessee (35.0816, -85.6325) is different from both the Blue Spring of Madison County, Alabama (34.7080, -86.5123) and the Blue Springs of Barbour County, Alabama (31.6636, -85.5067).

[18] U.S. Fish and Wildlife Service (1994) Endangered and threatened wildlife and plants; Determination of endangered status for the Royal Snail and Anthony’s Riversnail.  Federal Register 59: 17994 – 17998.  [FR-1994-04-15]

[19] The hypothesis I am offering here is now fair game for testing with a gene tree.  But if you are a bright young graduate student looking for thesis ideas, please first read Essay  the paper by Tom Coote [20].  Then read this essay, and the essays linked from it:

• Mitochondrial heterogeneity in Marstonia lustrica [3Aug20]

[20] Coote, T. W. (2019)  A phylogeny of Marstonia lustrica (Pilsbry 1890) (Gastropoda: Hydrobiidae) across its range.  Northeastern Naturalist 26: 672 – 683.

The Union in Tennessee! For lithoglyphid hydrobioids, that is.

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023b)  The Union in Tennessee!  For lithoglyphid hydrobioids, that is.  Pp 289 – 298 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other Essays.  FWGNA Project, Charleston, SC.

In last month’s episode [11July23], we marched south from Tennessee into Alabama with Gen. Ormsby Mitchel, the First Michigan Engineers and Mechanics Regiment, and Dr. W. H. DeCamp.  Capturing Huntsville on the morning of April 10, 1862, Mitchel’s forces moved rapidly both East and West to secure the vital Memphis & Charleston Railroad, by the end of the summer controlling 100 miles of riverbank on the north side of the Tennessee River.  And somewhere in the vicinity of Huntsville, sometime during that long and exciting summer of 1862, Dr. William Henry DeCamp, Surgeon US Army, collected a small sample of small lithoglyphid hydrobioids that turned out to be the first Somatogyrus described from the drainage of The Tennessee River, Somatogyrus currierianus (Lea 1863) [1, 2].

North Alabama campaign [3]

Last month we also reviewed what is known about the distribution of Somatogyrus elsewhere throughout the Tennessee drainage, both historic and modern.  East Tennessee populations have typically been identified with Tryon’s (1865) nomina S. parvulus and S. aureus [4], the former name prevailing in the tributary rivers above Knoxville, the latter further downstream in Knoxville and vicinity.  The Hiwassee hosts a well-documented population of Somatogyrus apparently trans-Appalachian in origin, and the little snails also pop up occasionally in TN-DEC macrobenthic samples collected from Chickamauga Creek near Chattanooga as well.

Middle Tennessee populations are less well-known, and if identified at all, are usually assigned the name Somatogyrus depressa, which Tryon (1862) used to describe populations in the Mississippi River at Davenport, Iowa [5].  These include a large population inhabiting the Duck River and a small population in the Harpeth River, a tributary of The Cumberland west of Nashville [6].

Between the East Tennessee populations identified as  S. parvulus/aureus and the Middle Tennessee populations identified as S. depressa are Dr. W. H. DeCamp’s old stomping grounds in North Alabama.  And last month we concluded that the key to understanding the entire, far-flung Somatogyrus fauna of the Tennessee River system is to understand that little sample of little snails Dr. DeCamp collected at “Huntsville” in 1862, sent to Isaac Lea and described as currieriana the following year [1].  Can Dr. DeCamp’s type population be found again?

That question weighed heavily on my mind as I tipped my hat to the Missus and boarded a westbound train for Alabama in August of 2021 [7].  The Huntsville Somatogyrus problem seemed closely analogous to that with which I had wrestled in the spring of 2020, searching for the type population of Melania perstriata, also described by Isaac Lea from Huntsville but in 1853, before the war [15Apr20].  The field notebook under my arm bulged with many water-stained pages of observations about the malacologically rich area toward which the Memphis & Charleston Railroad was bearing me that morning.

The city of Huntsville, I knew, had built up around a lovely, high-volume spring that was almost certainly the type locality of Melania perstriata, and which was quite likely the type locality of S. currierianus as well.  But I was also aware that in modern times the spring and its run have been channeled in concrete bulkheads through a formal midtown park and rendered essentially devoid of macrobenthos.  I didn’t see any Somatogyrus there in 2020, when I wasn’t seeing any Pleurocera (“Melania”) perstriata.

What to do?  It seemed to me that my best option would be to draw a series of concentric circles on my map around the Big Spring of Huntsville and try to find the Somatogyrus population next-closest.  So, upon arrival at the Huntsville Depot the next morning, I brushed the cinders from my frock coat, hired a mule-drawn hack at the livery, and set off down the Cottonville Pike for the Flint River about 10 miles distant.  This, I knew from experience, was the first body of water my mules would kick into substantial enough to host a population of Somatogyrus, travelling east.  And soon a second challenge, beyond the 150 years of landscape evolution boggling my eyes as we clip-clopped by the Starbucks, presented itself.

The Flint River Somatogyrus population is weird looking.  I figured a typical specimen in the Cherrytree montage I published in my [3Nov22] essay on Marstonia pachyta and figured a life-sized image of that same specimen again last month [11July23], and I’m going to show you a third time this month, marked Fl in the figure below.  The Flint River population seems to reach adulthood at an exceptionally small size, no more than maybe 2-3 mm shell length.  The shells they bear are also unusually light and – here’s the big shocker – typically show at least a little bit of umbilicus.  That’s right.  Flint River Somatogyrus look like Clappia.

I also figured the type of Lea’s S. currierianus last month, and I apologize about the quality of that image; the original picture was only about 5 mm in the monograph.  But Lea’s figure showed a much more robustly shelled snail, no umbilicus in evidence, as is typical for the genus.  Standing ankle-deep in the Flint River in the summer of 2021, holding the reins of a brace of wet mules in my left hand, I simply could not bring myself to designate the weird-looking little Somatogyrus crawling around at the bottom of the sawed-off trashcan I was holding in my right, as topotypic currierianus.

So, I re-mounted my asinine conveyance, and with a light touch of the whip continued eastward another 10 dusty miles or so beyond the Flint, to the sparkling waters of the Paint Rock River.  And there I found a somewhat larger-bodied and heavier-shelled population of Somatogyrus, a typical specimen from which is labeled PR above.  The Paint Rock population bears shells that are not umbilicate, and look fairly typical for the genus, and I thought at the time, might suit as modern topotypes.  Storing a sample in my watch pocket, I turned my wagon back into the setting sun, and returned to Huntsville for the night.

The next morning, I bought a fresh ticket at the station and boarded a westbound for Decatur and Tuscumbia.  And I resolved, as I did, to jump off at the first trestle [8], crossing the Limestone Creek about 15 miles west of the city.  She was making 30 miles an hour as we approached the bridge, but the drop was no more than 12 -15 feet, so I landed with the loss of no more than my hat, and vision in my left eye.

The shells borne by the Somatogyrus I plucked from Limestone Creek looked fairly typical, at least in the downstream precincts of Mooresville, at the railroad crossing.  See figure Lid above.  But as I made my way upstream, a new and intriguing phenomenon unfolded before my eyes.  The shells of the Limestone Creek Somatogyrus population began to open an umbilicus.  The photo below compares a shell collected downstream, 1 mile NE of Mooresville (Lid), to a shell collected about 12 miles upstream, at Capshaw (Liu).  Although the former is quite typical for Somatogyrus populations throughout the Tennessee drainage, the latter would conventionally be identified as Clappia.

And then it dawned upon me that I had seen this same phenomenon in the Powell River ten years previous – a Clappia population upstream blending into a Somatogyrus population downstream [9].  Both upstream populations seem to reach maturity at a smaller size, bear lighter shells, and prefer a substrate of woody debris on the margins.  The downstream populations are larger, more robustly shelled, and inhabit rocks midstream.  The parallel nature of this phenomenon, as it apparently manifests itself in both East Tennessee and North Alabama, suggested to me cryptic phenotypic plasticity of a high and aggravated nature.

All these thoughts tumbled through my mind as I walked the dusty road west toward Piney Creek, no more than a mile beyond Mooresville.  And what I found in Piney Creek reminded me very much of what I had seen in the Flint River on the previous day.  The Somatogyrus population of Piney Creek was exceptionally small-bodied, lightly shelled, and umbilicate, animals reaching adulthood not much more than 2 mm shell length, as depicted in Figure Pi above.

That evening I camped under the Decatur bridge, cooked a cup of chicory coffee in a tin can, and watched the Tennessee River flow by.  Actually, the river didn’t flow any more than I did.  Although this stretch of river would have been wild and free in 1862, the TVA closed Wheeler Dam about 30 miles downstream in 1936, backing the Tennessee River up almost 60 miles to Huntsville.  And all that met my eye that evening at the Decatur Bridge was slackwater swamp.

How many molluscan lives were lost as those flat, scummy waters inundated the historic Muscle Shoals between Florence and Decatur, I wondered to myself, as the sun set.  How many millions of unionid mussels, how many billions of pleurocerid snails?  Throughout the nineteenth century and into the twentieth, scores of Melania, Anculosa, Leptoxis, Pleurocera, Trypanostoma, Goniobasis, Lithasia, Angitrema, Strephobasis, and Eurycaelon were described and re-described from the rivers and streams around Muscle Shoals [10].  The pleurocerid populations inhabiting the roiling waters of that mighty river, bearing heavier, more robust shells, were typically assigned Latin nomina different from more lightly shelled populations inhabiting the gentler tributaries.

The Pleurocera canaliculata population inhabiting the main Tennessee River here at Decatur, I knew, extends up nearby Limestone Creek, where they were described as Melania pyrenella by Conrad in 1834. Historic nomina such as Conrad’s pyrenella, although now relegated to synonymy [11], nevertheless have demonstrable utility to describe morphological forms not apparently correlated with reproductive isolation, possibly ecophenotypic in origin.  We have suggested that such nomina, especially those around which some published literature has subsequently developed, be preserved at the subspecific level by virtue of their indexing function.

Similarly.  In 1906 Bryant Walker described seven species of Somatogyrus from the Muscle Shoals area, all of which bore robust shells, apparently adapted to large rivers with strong current [12].  Figure Sh above shows a typical specimen of Walker’s S. tennesseensis  from the Florida State Museum (cat. 83116), collected at “Shoals Creek near mouth with Tennessee River” date unknown.  That big-river shell morphology seems to match the image of Lea’s currierianus (see last month) better than any of the populations inhabiting the smaller tributary waters today.  But alas, the Somatogyrus of Muscle Shoals were buried under the slackwater with the unionids and the pleurocerids in 1936.  Gone With The Swamp.

Then by analogy with the better studied pleurocerids, we suggest that the following nomina are junior synonyms of Somatogyrus currierianus (Lea 1863):  aureus Tryon 1865, excavatus Walker 1906, humerosus Walker 1906, parvulus Tryon 1865, quadratus Walker 1906, sargenti Pilsbry 1895, strengi Pilsbry & Walker 1906, substriatus Walker 1906, and tennesseensis Walker 1906 [4, 12, 14].

And extending the analogy further.  The evidence reviewed above suggests that the populations described by Bryant Walker in 1904 as Somatogyrus umbilicata [15], separated by him into a new genus Clappia in 1909 [16], are lightly shelled upstream variants of Somatogyrus currierianus.  We therefore propose that Walker’s nomen umbilicata be lowered to subspecific status under Lea’s S. currierianus.

And in conclusion, we take this opportunity to remind our readership once again that the FWGNA has adopted the definition of the word “subspecies” standard since the Modern Synthesis, “populations of the same species in different geographic locations, with one or more distinguishing traits” [17].  Although there certainly may be some heritable basis for the umbilicus demonstrated by the shells of some small river Somatogyrus populations, and indeed for all the remarkable shell variety of all the remarkable freshwater malacofauna of North Alabama, ecophenotypic origins are at least equally likely.

Notes

[1] Lea, I (1863) Descriptions of fourteen new species of Melanidae and one Paludina.  Proceedings of the Academy of Natural Sciences of Philadelphia 4: 154 – 156.

[2] Lea, I (1866)  New Unionidae, Melanidae, etc., chiefly of the United States.  Journal of the Academy of Natural Sciences of Philadelphia Series 2, 6: 113 – 187.

[3] This is a small detail from a map of Alabama and Mississippi published by the United States Coast Survey in 1865.  Retrieved from the Library of Congress here: https://www.loc.gov/resource/g3980.cw0259500/

I added the colored marks and notes.

[4] Tryon, G. W. Jr. (1865)   Descriptions of new species of Amnicola, Pomatiopsis, Somatogyrus, Gabbia, Hydrobia and Rissoa.  American Journal of Conchology 1: 219-222, pl 22, figs 5-13.

[5] Tryon, G. W. (1862)  Notes on American fresh water shells, with descriptions of two new species.  Proceedings of the Academy of Natural Sciences of Philadelphia 14: 451 – 452.  I really think that Somatogyrus populations of the main Mississippi River are today best identified as Somatogyrus integra (Say 1829).

[6] Here’s a download of all 2,152 the Somatogyrus occurrences in the GBIF, as of 17Oct22: GBIF.org (17 October 2022) GBIF Occurrence Download https://doi.org/10.15468/dl.nv3tjh

[7] No, I drove I-20 to I-75 like everybody else these days and spent two hours in the Atlanta traffic.

[8] Actually, a westbound train from Huntsville will cross Indian Ck, Bradley Ck, and Beaverdam Ck before arriving at Limestone Ck.  None of these smaller streams seems to host a Somatogyrus population today.

[9] For a review of Bryant Walker’s contributions to our understanding of the hydrobioid genera Somatogyrus and Clappia, together with my own personal observations from East Tennessee on these enigmatic taxa, see:

• Bryant Walker’s Sense of Fairness [5Nov12]
• On getting Clappia in Tennessee [3Dec12]

[10] The actual count of pleurocerid species inhabiting the waters of North Alabama today totals ten: Leptoxis praerosa, L. crassa, Lithasia armigera, L. verrucosa, Pleurocera canaliculata (2ssp), P. clavaeformis (2 ssp.), P. laqueata, P. nassula, P. simplex, P. troostiana (3 ssp).

[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]  For a discussion of these important results, see:

• Pleurocera acuta is Pleurocera canaliculata [3June13]
• Pleurocera canaliculata and the process of scientific discovery [18June13]

[12] Walker. B. (1906)  New and little known species of Amnicolidae.  Nautilus 19: 97-100, 114-117.  In this paper Walker (solo) described six Somatogyrus from Shoal Creek and the main Tennessee River around Florence, Alabama: substriatus, humerosus, quadratus, excavatus, tennesseenis, and biangulatus [13].  He also described strengi from the same area, which he credited to “Pilsbry & Walker.”

[13] I think that the populations Walker described as Somatogyrus biangulatus in 1906 may indeed have been biologically distinct, and now extinct.

[14] Pilsbry, H.A. (1895) New forms of American shells. Nautilus 8(9): 102.

[15] Walker, B. (1904)  New species of Somatogyrus. Nautilus 17: 133 - 142.

[16] Walker, B. (1909)  New Amnicolidae from Alabama. Nautilus 22: 85 - 90.

[17] For an elaboration of the concept, see:

• What is a subspecies?  [4Feb14]
• What subspecies are not. [5Mar14]