Lymnaea (Galba) bulimoides and the NCBI GenDump, with lecture notes on the scientific method

Looking back over my essays of the last two months [13Feb25, 11Mar25], as well as my essay of February a year ago [13Feb24], I feel as though my efforts to review the historical and technical background behind my Oregon field trip for L. bulimoides last summer have been largely successful.  But there is a human context as well, to which I fear I have given short shrift.

My faithful readership will (I trust) remember our old friend Dr. Phillippe Jarne of the French National Centre for Scientific Research (CEFE-CNRS) in Montpellier [1], yes?  It was Philippe who introduced me electronically to Dr. Pilar (Pili) Alda back in 2017, when she was working as a postdoc in the laboratory of Dr. Sylvie Hurtrez-Bousses at the Universite’ de Montpellier.  Pili was the lead author on both our (2018) multiplex PCR paper on Galba [3] and that huge (2021) molecular phylogenetic review of the subgenus Galba worldwide [4].  She is currently at CONICET-CERZOS, the Argentinian National Research Agency in Bahia Blanca.

So, I have long harbored suspicions about the lymnaeid fauna of Western North America.  Those suspicions compounded when I began working with Bruce Stephen on the Freshwater Gastropods of the Great Plains project in 2020, expecting to find Lymnaea (Galba) bulimoides in that region, finding  L. cubensis/viator and L. cockerelli but nothing that matched Isaac Lea’s 1840 bulimoides types from Oregon [5] whatsoever.  I promoted my suspicions to the status of an hypothesis in a pair of essays posted on this blog in February [13Feb24] and March [12Mar24] of last year, ultimately concluding that while “huge international teams” have published “mountains of research” on the evolutionary relationships among all the other hosts of Fasciola worldwide, here in the USA we have “zero authentic DNA sequences” for any population of our own L. bulimoides.

Lymnaea (Galba) of the American West [6]

Shortly after that, I began swapping emails with Philippe and Pili.  And over the course of the following months, from mid-March to early May of last year, a miniature online symposium developed on evolutionary relationships among the Galba populations of the western USA, ultimately growing to include Patrice David (CEFE-CNRS), Jean-Pierre Pointier (Universite de Perpignan), and Sam Loker and Martina Laidemitt of the University of New Mexico.  I confess that the main item on my agenda [7] was to find somebody else – anybody else – to fly out to Oregon and collect us a bona fide, gold-seal sample of L. bulimoides.  But ultimately, I found myself volunteering.  And Pili already had plans to return to Montpellier in September, and volunteered to do the sequencing and analysis.

And so it came to pass that my wife and I boarded Delta Flight 954 bound for Portland on July 31, 2024, to return, five days later [8], defeated and humiliated by a basommatophoran pulmonate.  See my essays of February[13Feb25] and March [11Mar25] for a painful recounting.  But tucked into my shirt pocket were those N = 2 individual L. bulimoides that Ms. Courtney Hendrickson had preserved from Gahr Pond in the spring of 2023.  And those I forwarded onward to Philippe and Pili in August.

And in early November, Pili sent us her results.  She sequenced the same four genes that we had analyzed in our 2021 collaboration: the mitochondrial CO1 and 16S, and the nuclear ITS1 and ITS2.   And her results looked like a phylogenetic shotgun blast.

For some reason I always look at CO1 first, and the closest CO1 match to our two Gahr Pond bulimoides anywhere in GenBank was 90 – 91% to Galba cousini from Ecuador.  That strikingly low similarity with anything else supported my primary hypothesis, that all DNA sequences previously deposited into GenBank as “bulimoides” were spurious [13Feb24].  The result did not support my speculation (based on shell morphology) that South American L. cousini might be conspecific with North American L. bulimoides – 10% CO1 divergence is very significant in pulmonate phylogenetics [9].  But it left me with a fig leaf.  The evolutionary relationship between bulimoides and cousini appeared to be closer than any other.

Pili’s 16S mtDNA results also supported my primary hypothesis.  Our pair of Gahr Pond 16S sequences were around 96% similar to maybe 50 – 60 sequences already deposited in GenBank, including truncatula and “humilis” from the former Soviet Republic of Georgia, Brazilian “truncatula,” Japanese “pacifica,” junk from everywhere.  Simply no bona fide matches.

One of Pili’s ITS1 sequences was too short to be informative, but the other was wildly unique – no match closer than 82% in all of GenBank.

Our Gahr Pond ITS2 results, by striking contrast, did hit close matches to a pair of sequences already in GenBank, uploaded in 2020 by the English researchers A. J. Saadi and colleagues in connection with a molecular phylogenetic study of the freshwater pulmonates [10].  Working from their laboratory at the University of Nottingham, Saadi et al. sequenced 4000 nucleotides from the rRNA gene cluster of 39 individual snails, including part of the 5.8S gene, the complete ITS2 region, and almost the entire 28S gene.  They missed the ITS1 region (just upstream from 5.8S) and didn’t touch the mitochondria at all.

The closest of the close matches to our Gahr Pond bulimoides was 98.2% to a sequence from a snail that Saadi and colleagues identified as “Polyrhtis apicina,” but was subsequently emended to Stagnicola or “Ladislavella” apicina, with collection location unknown and collector unknown.  Absolute garbage.  Sometimes I think the NCBI should rename its GenBank to GenDump.

The Willamette Valley of Oregon

But the other close match, 97.6%, was to a sequence from a snail that Saadi identified as “Bakerilymnaea bulimoides (= Fossaria bulimoides),” subsequently listed in GenBank as Galba bulimoides [11], from “Corner of Alvadore Road, Lane County, OR, USA” with the collector identified as our old buddy Dwight Taylor [13].

The corners of Alvadore Road – there are two of them about 500 m apart, actually – are just 40 km south of the Bellfountain Road site I had targeted back in August as the ideal type locality for Lymnaea (Galba) bulimoides.  How a sample of bona fide L. bulimoides, correctly identified with good locality data, found its way from Dwight Taylor’s 1970s-era collection bucket into the buzzing thermal cyclers of Nottingham, England, I cannot imagine.

So, my hypothesis was confirmed, with an asterisk.  In my post of [13Feb24] I had written:

“Meanwhile here in the USA, the richest country on earth, the leader of the free world, we have zero authentic sequences for any population of our own Lymnaea (Galba) bulimoides, known to be an important host of livestock fluke across the Pacific Northwest since 1929.”

That turned out to be sort-of true, but I should have footnoted, “except two rRNA sequences contributed by Saadi et al, one of which was misidentified and utterly useless.”  All the other (really rather few) sequences labelled bulimoides in GenBank were spurious, most notably the 16S/CO1 pair from Oklahoma uploaded by Remigio [14, 15] that caused Correa [16] and Alda [4] and me myself a sinner [7Aug12] to hypothesize that bulimoides might be a junior synonym of cubensis/viator.

I taught freshman biology at the College of Charleston for many years, although I was never any good at it, to judge from student evaluations, which were the only criterion that mattered when the time came for my own annual evaluation.  And the first lecture of the semester, which most of the students missed, because they were all still standing in line at registration or lost on campus, was “The Nature of Science, and The Science of Nature.”  I kicked it off with a blanket statement that this was to be the most important lecture of the semester, and the material I intended to review was so complex and so other-worldly and so difficult to grasp that even most professional scientists never figure it out in our entire careers.

Science is the construction of testable hypotheses about the natural world.  The process by which science moves forward is called “the scientific method.”  But please do not confuse the product with the process.  It is entirely possible to use the scientific method to determine (for example) what color box of detergent is most attractive to housewives shopping in the grocery store.  Just because some guy is wearing a white lab coat, conducting experiments and collecting data in a systematic fashion, does not mean that he is a scientist.  The subject matter must be the natural world.

The scientific method begins with a question, like “What is Lymnaea bulimoides?” [13Feb24]  Then, good scientists do library research – a lot of it – which together with experience and intuition from a fundamental understanding of the foundations of their discipline, enable them to precisely frame a testable hypothesis about the natural world, like “there is not a worker in the field today – not malacologist, nor parasitologist, nor veterinarian, nor guardian of the public health – who could identify a bona fide Lymnaea (Galba) bulimoides if it bit him on the boot toe” [13Feb25].

Then comes the gathering of data to test that hypothesis, such the expedition to Oregon and subsequent DNA sequencing I have now spent three blog posts detailing.  Then data analysis – GenBank fishing in our case – and conclusion.  Hypothesis true.

The Scientific Method [17]

As I delivered my lecture I was, of course, scrawling the steps of the scientific method on the chalkboard in some grossly graphic fashion.  I would then suddenly turn to my students and assert that in actual practice, most of what passes for science of the present day is done backwards.  Huge research groups and agencies – I usually mentioned NASA, for example – typically begin with data collection, then try to find an hypothesis within those data somehow, and then finally, maybe, go to the library to see if anybody had published anything on an hypothesis like theirs before.

It has now gotten to the point, I used to wag my finger at my half-empty lecture hall of freshmen, that my colleagues often segregate science conducted according to the diagram I have outlined on the chalkboard as “hypothesis-driven research.”  But if your research is not driven by a precisely-framed, rigorously-testable hypothesis about the natural world, you are not doing science, you are just screwing around with test tubes.

Now turning to you, my present readership. The construction of a gene tree is not and cannot be the beginning of a research effort!  You cannot derive an hypothesis from a gene tree.  The only appropriate application for a gene tree is to test an hypothesis that you have clearly stated a priori on the basis of library research, field experience, and biological intuition.

We do not need any more DNA sequences from random freshwater gastropods shoveled into the NCBI GenDump.  We do not need any more odd-lot molecular phylogenies of random freshwater gastropod genera or families – we don’t understand the ones we’ve got now.  We do not need more data; we do not need more analysis.  What we need are more precisely-framed, rigorously-testable hypotheses.  Which can only come from a thorough education in evolutionary science, a firm understanding of the biology of the remarkable creatures to which we have dedicated our careers, rigorous scholarship and field experience, lots of both.

So finally, returning to our research program on Lymnaea (Galba) bulimoides.  We have proceeded in orderly fashion from question to hypothesis to data to analysis to conclusion.  But there remains yet one final box in the flow chart I scrawled on the blackboard in front of my doe-eyed freshmen – a box that the International Bulimoides Study Team has not as yet checked.  And there will be a fourth essay in this series, eventually.  But next month we are moving on to other topics.  So, stay tuned.

Notes

[1] See the brief bio and cute little 2012 photo of Philippe and his postdoc Patrice David [2] in:

• The American Galba and The French Connection [7June21]

[2] Patrice would subsequently rocket to malacological stardom by discovering:

• Cytoplasmic male sterility in Physa! [9June22]
• Cytoplasmic male sterility in the Physa of the Snake River [7Aug24]

[3] 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].  For a review, see:

• The American Galba: Sex, Wrecks, and Multiplex [22June21]

[4] 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].  For a review, see:

• Exactly 3ish American Galba [6July21] 

[5] Isaac Lea initially described Lymnaea bulimoides in brief Latinate form in 1841, with more complete English description in 1844:

• Lea, I (1841) On fresh water and land shells (continued).  Proceedings of the American Philosophical Society 2(17): 30 – 34.
• Lea, I. (1844/46) Continuation of Mr. Lea’s paper on fresh water and land shells.  Transactions of the American Philosophical Society 9(1): 1 – 31.

[6] Lymnaea bulimoides from Alvadore Road, L. viator from Alda [4], L. cockerelli from Bosque del Apache, NM.  Photo credits J-P. Pointier.

 

[7] Actually, the evolutionary relationships of the mysterious “Bosque del Apache” population from New Mexico may have been a topic of greater discussion than Lymnaea bulimoides.  Originally identified as Galba cubensis in the gigantic 2021 paper we had all coauthored with Pili [4], molecular data kicked the Bosque del Apache population out as specifically separate.  Ultimately the research I reported in my essay of [12Mar24], together with the shell morphology, convinced the entire working group that “Galba sp Bosque del Apache” must have been Lymnaea (Galba) cockerelli.  Grist, perhaps, for a future post.

 

[8] My exceptionally keen-eyed readership might note that my essays of February and March covered three days only.  Shary and I toured the Oregon Coast on Aug 3, and the Columbia Gorge on Aug 4.  It was the least I could do for her.  She was very patient with me.

 

[9] As a rule of thumb, a CO1 sequence divergence of 5% or more suggests speciation in the freshwater pulmonates.  For my rationale, see:

• The Lymnaeidae 2012: stagnalis yardstick [4June12] 

[10] Saadi, A.J., A. Davison and C.M Wade (2020) Molecular phylogeny of freshwater snails and limpets (Panpulmonata: Hygrophila)  Zoological Journal of the Linnean Society 190: 518 – 531.

 

[11] Here, writ in flickering pixels on the face of an obscure blog, is the Embarrassment of International Malacology.  Six generic names – Stagnicola, Ladislavella, Polyrytis, Bakerilymnaea, Fossaria, and Galba – for a single biological species that ought never to have been split from Lamarck’s (1799) Lymnaea [12].  Please stop making up ridiculous names for random subsets of mollusks, everybody!  You make us look like a bunch of clueless hacks.  Which we are.  But must we broadcast that sad fact to the world?

 

[12] For a bracing splash of 1951 common sense in the rouged face of 21st century systematic malacology, see

• The Classification of the Lymnaeidae [28Dec06].

[13] My faithful readership will certainly remember Dwight Taylor as the author of the great Snake River Physa scandal [12Mar08, 14May24, 11June24].  Early in his career he (correctly) recognized the specific status of Lymnaea cockerelli [12Mar24] and (cavalierly) detonated the genus Helisoma [11Apr08].

 

[14] Remigio, E.A. and Hebert, P.D. (2003) Testing the utility of partial COI sequences for phylogenetic estimates of gastropod relationships.  Molecular Phylogenetics and Evolution 29 (3): 641-647.

 

[15] Remigio, E.A. (2002) Molecular phylogenetic relationships in the aquatic snail genus Lymnaea, the intermediate host of the causative agent of fascioliasis: insights from broader taxon sampling, Parasitol. Res. 88 (7), 687-696.

 

[16] 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.  I reviewed that paper in my post:

• The Lymnaeidae 2012: Fossarine Football [7Aug12]

[17] Graphic from The Biologos Forum.

The Phantom Lymnaeid of the Pacific Northwest

Editor’s Note – This is the second installment in a projected four-part series on Lymnaea (Galba) bulimoides in Oregon.  You might want to refresh your memory of last month’s post [13Feb25] before proceeding.

My goodness, the Willamette Valley is wide open – fields and pasturelands stretching to the horizon in all directions.  My target, early on the morning of August 2, 2024, was a ditch along the west side of Bellfountain Road 5 miles SW of Corvallis, Oregon, in the “south-east corner of section 18, range 5 west, township 12 south.”  That ditch, as best I could figure, was the study site of a British Columbian biologist named Greg R. Foster, over 50 years ago.

The results of Foster’s charming little 1971 mark-recapture study [1], entitled “Winter vagility of the aquatic snail Lymnaea (Galba) bulimoides,” do not concern us here.  But by all criteria – its accessibility, its protection, and the biological characterization of the crappy little amphibious lymnaeid population there dwelling, Foster’s study site stands even unto the present day as the best candidate to restrict the type locality of the intermediate host of livestock liver fluke in the Pacific Northwest.

By Bellfountain Road, 2Aug24

Foster’s study was conducted over a period of ten weeks from December 26 – March 8, 1969, quite the surprising time window, if you stop to consider it, for so northerly a latitude.  He explained this peculiarity in the first paragraph of his discussion, as follows:

“In many aspects concerning life cycle and ecology L. bulimoides is quite similar to the aquatic snail Aplexa hypnorum (L.) found in the Molenpolder at Yerseke, Holland (Den Hartog & De Wolf, 1962). Both are found in shallow ditches on soil of about the same type. Both are extremely tolerant of cold and desiccation. Both have life spans coinciding with the time between the end of the summer drought in one year and the beginning of the drought in the next year.”

I had flagged the Den Hartog paper [2] in the early-1990s, when I was doing research for my book [3], collecting all the diverse pulmonate life cycles into a single synthesis on pp 156 – 162.  And I myself had a bit of field experience hunting Aplexa in Michigan, as well as the (ecologically analogous) Physa carolinae in our local swamps right here in the Southeastern coastal plain [4].  And I was quite well aware that Aplexa populations cannot be sampled in the summer.  In retrospect, perhaps I should have taken Foster’s analogy as a warning.

Foster’s follow-up paper of 1973 [5], “Soil type and habitat of the aquatic snail Lymnaea (Galba) bulimoides during the dry season,” was even more interesting, and even more revealing of the peculiar biology of the critters I was determined to sample this day.  This second study was conducted in July and August of 1969 over a much larger area, “publicly owned ditches, streams and pastures that could be reached with a truck and then by foot” in a large township-and-range block around Corvallis.  Foster used a bucket auger to collect 456 soil samples to a depth of 3 inches, carrying each back to the lab and submerging each in water.  A total of 60 living L. bulimoides were collected, depending on soil type.

View SW, from Bellfountain Rd.

If Greg R. Foster had any observations on populations of L. bulimoides living anywhere above the surface of the soil anywhere in NW Oregon in the summer of 1969, he did not mention them.  Again, in retrospect, I might have taken note.

 

I had prepared myself by inspecting the fields along Bellfountain Road using that little “Street View” man at the lower right corner of Google Maps, which showed a soggy fallow field, with significant standing water, and several inches of water dribbling through the roadside ditch.  That was the last time the Googlemobile had passed that way, in April of 2024.

 

The situation that greeted my eye on the morning of August 2, 2024, however, was Not That.  If I have ever seen a soil so dry and hard as the bottom of that ditch, or smelled grass so brown and brittle, or felt a wind so arid as that which stung my cheek that morning, standing on the verge of that road from nowhere to nowhere in the middle of flat nothing Oregon, I cannot remember it.

 

Ah, but there were dead shells in that ditch, L. bulimoides sure enough, in some places quite a lot of them.  And I jumped the ditch and stomped through the hayfield, very much as I had at the Gahr Farm the previous afternoon, and additional shell remains were not uncommon.  And at one point I even stumbled upon a little pile of Helisoma trivolvis shells, frozen in death, confirming that the water levels here had at some day in the recent past been significant.  But today was not that day.

The Oregon Snail Team! [6]

And I had a late-morning appointment to keep with my buddy Bill Gerth at the OSU Department of Fisheries, Wildlife and Conservation.  I trust my readership will remember Bill from his introduction last month, yes?  I was pleased to meet Courtney Hendrickson in Bill’s lab as well, along with parasitologist Mike Kent.  Courtney gifted me that small sample of N = 2 L. bulimoides she had collected at Gahr Pond in May of 2023, for which I will remain eternally grateful.  Bill offered a suggestion on a locality where I should be able to find water, even at this date so advanced in the summer, a creek just east of the little city of Halsey, about 15 miles south of Corvallis.  And he pointed me to the local Fred Meyer Department Store, where I was able to purchase a shovel and a 5-gallon bucket.

 

And I was off again.  Halsey (pop 904), founded on the Oregon & California railway in 1872, was at one time famous for the iconic Cross Brothers Seed and Grain warehouse, towering 152 feet above the flat ryegrass fields of western Linn County [7].  And it was only there, well into the third day of my Oregon Expedition, that the true enormity of the challenge before me was finally laid bare.

 

My spirits leapt upon arrival at Spoon Creek, 2 km east of town, as pretty an agricultural ditch as I can ever remember stomping down into (A).  The water was surprisingly clear and cool; the habitat surprisingly rich and diverse.  Physa acuta, Helisoma trivolvis, and Gyraulus parvus were all common.  And without any difficulty I was able to survey extensive mud banks of the sort where, in The East, crappy little amphibious lymnaeids would have been jumping into my sample vials.  But alas, no lymnaeid snails of any rank or description volunteered that morning, nor did any evidence thereof present itself to eyes that ached to see it, not so much as a dry shell.

What is the problem here?  What is the problem?  Too baffled to be dispirited, I returned to my rental car, reversed course back toward town, and crossed the railroad tracks 2,000 m west.  There between the tracks and a gravel service road ran a bone-dry ditch choaked with grass, weeds, and roadside litter (B).  And in that shallow ditch I found L. bulimoides shells.  Lots of them.  But none alive – no water.

 

Returning to my car and driving another 200 meters west – honestly, I should have walked – I crossed another agricultural ditch, this one green and carrying water (C).  It was marked as an intermittent creek on USGS maps, much smaller than Spoon Creek, without the habitat diversity.  I found sparse populations of both Lymnaea elodes and Helisoma trivolvis in the grasses there, however, and a singleton individual Succinea grazing along the water’s edge, mimicking an L. bulimoides so startlingly I almost had a heart attack, three days building [8].

 

But absolutely no bulimoides in green ditch (C), nor any shell, nor any sign thereof.  There you have it, in a triptych.  A linear transect of 2,200 meters returned no evidence that bulimoides had ever inhabited a summer-watered habitat (A), lots of evidence of bulimoides in a summer-dry habitat (B), and no evidence of bulimoides in a second summer-watered habitat (C).  Lymnaea bulimoides populations are obligately vernal.  They cannot be found in the summer, not in this part of the world, anyway.

But I had time, spirit and wherewithal for one last Hail Mary.  Back to the ditch along Bellfountain Road I drove, determined to replicate Greg R. Foster’s experiments from the summer of 1969.  I picked a low point near a drainage pipe, where dead shells had accumulated.  Then, shiny new Fred Meyer shovel flashing in the hot August sun, I chopped – literally chopped – rock hard earth out of the ditch down to a depth of maybe 10 inches and loaded it into my crisp orange five-gallon bucket.  This I carried back to the Airbnb my wife and I had rented in town, hosed down, stirred and waited.  Stirred and waited.  Stirred.  Waited overnight.  Nothing.

 

My wife and I dropped by Bill’s house on our way out of town the next morning.  He had indicated that he could make some use of a slightly tarnished shovel and a muddy five-gallon bucket, the like of which I just happened to have in the hatchback of our rental car.  Bill promised that he and the OSU students would monitor G. R. Foster’s Bellfountain Road site, and return in the winter, with the rains.

 

I myself had been completely skunked – humiliated – by Lymnaea (Galba) bulimoides.  Even unto the present day, over a malacological career spanning 50 years, I have yet to see one on the hoof.  But tucked into my shirt pocket as we boarded Delta Flight 675 for home was a glass vial of alcohol.  And in that alcohol were exactly N = 2 bona fide bulimoides from Gahr Pond, courtesy of Ms. Courtney Hendrickson.  Might the centuries-old confusion over the very identity of the Phantom Lymnaeid of the Pacific Northwest somehow yet be resolved?  Tune in next time.

 

Notes

 

[1] Foster, G.R. (1971)  Winter vagility of the aquatic snail Lymnaea (Galba) bulimoides Lea.  Basteria 35: 63 – 72.

 

[2] Den Hartog, C., and L. DeWolf (1962)  The life cycle of the water snail Aplexa hypnorum. Basteria 26: 61-88.

 

[3] Dillon, R.T., Jr. (2000) The Ecology of Freshwater Molluscs.  Cambridge University Press, UK.  509 pp.

 

[4] Wethington, A.R., J. Wise, and R. T. Dillon (2009) Genetic and morphological characterization of the Physidae of South Carolina (Pulmonata: Basommatophora), with description of a new species.  The Nautilus 123: 282-292. [pdf]  For more, see:

• TRUE CONFESSIONS: I described a new species [7Apr10]

[5] Foster, G.R. (1973) Soil type and habitat of the aquatic snail Lymnaea (Galba) bulimoides Lea during the dry season Basteria 37: 41 – 46.

 

[6] From left, Emilee Mowlds, Bill Gerth, Courtney Hendrickson & McKenna Varela.

 

[7] Alas, the top off the derelict structure was demolished in 2012, due to concerns over its structural integrity.

 

[8] Yes, in my field notes I wrote, “Succinea gave me a heart attack.”  Death by Stylommatophoran.  My goodness, we malacologists are a strange and tender lot, aren’t we?

Oregon, bulimoides, or bust

Editor's Note – Exactly one year ago, on [13Feb24], I posted an essay in the columns of this blog asking the question, “What is Lymnaea bulimoides?”  And I concluded that essay, “Malacologists of America, we must do better.”  Here is my effort.

L. bulimoides Gahr Pond

Thomas Nuttall (1786 – 1859) was a man of distinction [1].  He was among the first naturalists to explore Arkansas, among the first to botanize California, and the author of the first field guide to the North American birds.  The breadth and depth of his experience with the natural history of temperate America was unequalled in his day, arguably since.  And of the 400,000 pioneers who travelled the Oregon Trail west from its opening in the early 1810s through its heyday in the 1840s – 1860s, Thomas Nuttall was one of the very, very few who ever came back east again.

And packed deep in the luggage he carried with him aboard the merchant brig Alert in 1836 [2], bound from Monterey to Boston with a cargo of cowhides, was the world’s first sample of crappy little amphibious lymnaeids that Isaac Lea [3] ultimately described as Lymnaea bulimoides [4].  And as my wife and I boarded Delta Flight 954 for Portland on the morning of July 31, 2024, in that one tiny distinction, I meant to join him.

 

Never has a freshwater gastropod subsequently so important been subsequently so widely misunderstood.  Lymnaea (Galba) bulimoides is the primary intermediate host of Fasciola hepatica – the livestock liver fluke – in the Pacific Northwest.

Fasciola is a digenetic trematode, which means that it has two hosts, a primary host, typically hooved livestock [5], and an intermediate host, typically a lymnaeid snail.  The worm infects the liver of its primary host, laying eggs which are defecated.  Those eggs hatch into swimming miracidium larvae which find a snail, burrow in, and develop into rediae, which in turn shed swimming cercaria larvae. 

 

In all of those details, Fasciola is no different from the better known fluke Schistosoma.  But unlike Schistosoma, the cercariae do not burrow into the skin of their primary hosts but rather encyst on grasses and vegetation.  And the cysts must be eaten by the primary host to complete the life cycle.

Life cycle of Fasciola [6]

So, from the standpoint of the fluke, the best environment would be a pasture cycling wet to dry, inhabited by an amphibious lymnaeid that might be exposed to swimming miracidia and shed swimming cercariae during the wet season, then drying so that the cysts might be grazed over by livestock.  Remember that.  That will be a key to understanding the remainder of this essay, and next month’s as well.

 

Liver flukes are a problem for the livestock industry [5] on six continents, and significant research efforts have been directed toward understanding the crappy little amphibious lymnaeids that host them worldwide for many years [7].  Except in the Pacific Northwest.  Where there is not a worker in the field today – not malacologist, nor parasitologist, nor veterinarian, nor guardian of the public health – who could identify a bona fide Lymnaea (Galba) bulimoides if it bit him on the boot toe.  Or at least, that was my hypothesis, as I boarded Delta Flight 954.

 

My library and museum research over several years previous had revealed to me what appeared to be repeated and systematic confusion between Lymnaea (Galba) bulimoides and Lymnaea (Galba) cubensis/viator, a similarly small, similarly amphibious, similarly susceptible lymnaeid much more widely distributed across The Americas, North and South [8].  That confusion seemed to have its origins in the late 19th century, redoubling in the early 20th, with the description of Lymnaea (Galba)  cockerelli, a third distinct biological species sometimes co-occurring with bulimoides in mixed populations [9].

 

I became convinced of a widespread, systematic, three-way confusion in early 2024 but had no evidence to support it, much less solve the problem.  To test that hypothesis, I needed a control, and none was to be had.  Thomas Nuttall’s original sample, surviving the perilous voyage around The Horn with their collector, was described by Isaac Lea as simply coming from “Hab. Oregon.”  In 1841, “Oregon” included all or part of five U.S. States, and much of British Columbia.

 

So, the first step out of the darkness, it seemed to me as I settled into my narrow seat early that July morning, would be to restrict the type locality of Lymnaea bulimoides to some more precise spot.  And then to sample and characterize the population of crappy little, amphibious lymnaeids inhabiting that spot as a standard, against which all other populations of lymnaeids might be compared.

The ideal type locality should be well-characterized, accessible, and protected.  Thus, folded in my shirt pocket that morning was a map of Oregon I had printed off line with a pin dropped on 44.5229, -123.3377, a drainage ditch by Bellfountain Road about 8 km SW of Corvallis where, as best I could figure, one Greg R. Foster had conducted the only decent studies of the biology of L. bulimoides ever published in the scientific literature, way back in 1969.  More about those studies [10] next month.

 

And there were other pins dropped on my map as well.  In addition to establishing a type locality, I very much wanted to find at least two additional populations of bona fide L. bulimoides to get some feel for intraspecific variation – one north of Corvallis, and one south.  For the former, I had researched online quite a few museum collections of apparently bona fide L. bulimoides in the Portland area, perhaps 70 miles north of Corvallis. And I had also marked the bowl of a rolling hayfield in a lovely and remote corner of Yamhill County about 40 miles north of Corvallis, locality courtesy of Ms. Courtney Hendrickson of Oregon State University, and the hero of our story, Mr. William (Bill) Gerth.

 

Bill is a senior faculty research assistant in the OSU Department of Fisheries, Wildlife, and Conservation Sciences in Corvallis, and a longtime friend of the FWGNA Project.  I could not name a cheerier or more enthusiastic colleague.  I had emailed Bill several days before flying off to Oregon, just to touch base, and he replied almost immediately with a gang of students and coworkers on the CC line all interested and eager to help.

 

And attached to his email was the jpeg that opened this essay, depicting a nice individual L. bulimoides collected by Ms. Hendrickson from a seasonal pond in a hayfield on the Gahr Farm property in Yamhill County. The itinerary I had outlined for myself and my lovely wife Shary, as we retrieved our luggage in the Portland airport and headed for the rental cars that hot July morning, was an ambitious one.

We drove north over the Columbia River that very afternoon, and into the state of Washington.  And my first noteworthy observation was made while still battling the urban sprawl of Vancouver: a population of very ordinary-looking Lymnaea (Galba) humilis inhabiting the muddy margins of a retention pond across Mill Plain Blvd from the Walmart (A).  I don’t suppose I was terribly surprised.  Those things are the Physa acuta of the Lymnaeidae.  But it was interesting to see our old friend humilis here in the Pacific Northwest, making cozy with the much more mysterious bulimoides I hoped to find, and the cubensis I rather hoped I would not.

 

The environment turned more propitious at Grass Valley Slough (B), but here we encountered the problem that would bedevil us for the remainder of our sojourn in the Pacific Northwest.  The slough was bone dry, baked hard as a rock.  I was most impressed by the dramatic accumulation of bleached Physa gyrina shells in the brittle mud at the culvert under Bybee Road, but finding no evidence of lymnaeid remains among them, neither shell nor meat, moved on.

 

Further north the topography evolved into rolling hills, the drainage improved, and scattered forest appeared.  And at point (C) I made an observation that forever changed my life [11].  Juga in a ditch.  This was a little roadside ditch, not three feet across, choked with grass, a place one would never expect to find a prosobranch gastropod of any sort back East, ever [12].  Yet Juga [14] does.  There simply is no substitute for field experience if one wants to understand the biology of a study organism, or indeed an entire Linnaean Family of study organisms, and I was once again reminded, harshly, that in the Pacific Northwest, I had none.

 At Battleground Lake (D) we reached the foothills of the Cascades, and finding the poorly drained fields and open pasturelands that best serve as habitat for the elusive L. bulimoides essentially gone, and the light failing, reversed our course for Portland, disappointed.  Tomorrow, I hoped, conditions might be more favorable.

Shary at Baker Cabin

The next morning we set our course east along the left bank of the Columbia River, swooping wide around the eastern suburbs of Portland toward the Willamette River valley to the south.  The freshwater gastropod fauna was gratifyingly diverse in the sloughs along the south bank of the big river (E), that of Kelly Creek (F) and several other sites in the Sandy and Clackamas River Valleys (G), rather less so [16].  My goodness, the day was turning hot.

 

All of the sites we visited that morning, and into the early afternoon, included some exposed mud bank, which would have been fine habitat for crappy little amphibious lymnaeids in The East but seemed devoid of molluscan life here in the environs of Portland.  We ran into the Oregon Trail at the historic Baker Cabin (H) and followed the trail down to its terminus at Oregon City (I).

 

Well, to be technical, Oregon City was the terminus of the Barlow Road section, a passage through The Cascades that did not open until 1846.  Thomas Nuttall pioneered the newly opening trail in 1834.  In those days the only route to Oregon was down the Columbia River, through the treacherous rapids at The Dalles.

 

My wife and I, on the other hand, opted to take I-205 and OR-18 south through the rich agricultural landscape of Yamhill County, now dry and brown in the August sun. The rotating sign in front of the bank was reading 103 degrees at 4:20 in the afternoon, when we passed through McMinnville on our way west toward Gahr Farm (J).

Bill’s colleague Courtney had thoughtfully alerted the landowner to expect visitors that afternoon and sent me a link to a map with a suggestion on a parking spot, as well as the precise coordinates [17] where she had collected N = 2 L. bulimoides in the spring of 2023, some 400 meters south through Farmer Gahr’s stubbly hayfield.  She added somewhat cryptically, however, “Just a heads up that the ponds can be a little tricky to find.”

 

My standard wardrobe for fieldwork is built on a foundation of hip boots over blue jeans, at least as much to protect my legs stomping though underbrush on my way to the creek as to protect my piggies upon arrival.  But the sun beat so mercilessly on Farmer Gahr’s fallow fields late that afternoon I changed into shorts and water shoes by  the desolate roadside, willing to pay the cost of few degrees of cooling in blood from my ankles.  And off I stomped toward an island of cattails flickering in the distance.

Alas, dry-rooted cattails were the only evidence that any pond had ever existed in the rolling hills of the Gahr Farm on August 1, 2024.  I staggered, dazed, from patch to patch, beating down through the willows to the Muddy Creek ditch, finding not puddle, nor pebble, nor polliwog.  The singleton bleached shell of Physa gyrina I ultimately recovered, in over an hour of pawing through brittle cane and cattail root, felt like a trophy.

Gahr Farm, 1Aug25

As I trudged back to our rental car, where my wife sweltered in the late afternoon sun [18], singleton Physa rattling dry in a vial in my chest pocket, I found myself meditating on the mantra, “Malacology in The West is different.”  And as the sun set on that exceptionally long, exceptionally hot day, southbound on OR-99W with Corvallis lit green on our GPS, a question crystallized.  Might any better fortune await me in Greg R. Foster’s ditch on the morrow?  Tune in next time.

Notes

 

[1] Most of the biographical information that opened this post came from:

• Nelson, John R. (2015) Thomas Nuttall: Pioneering Naturalist (1786 – 1859).  Bird Observer 43: Article 2.

[2] By remarkable coincidence, Richard Henry Dana was serving as an ordinary sailor on this very voyage, later to record the adventure in his famous memoir, “Two Years Before the Mast.”

 

[3] For a brief bio of “The Nestor of American Naturalists,” see:

• Isaac Lea Drives Me Nuts [5Nov19]

[4] Lea initially described Lymnaea bulimoides in brief Latinate form in 1841, with more complete English description in 1844:

• Lea, I (1841) On fresh water and land shells (continued).  Proceedings of the American Philosophical Society 2(17): 30 – 34.
• Lea, I. (1844/46) Continuation of Mr. Lea’s paper on fresh water and land shells.  Transactions of the American Philosophical Society 9(1): 1 – 31.

[5] Human cases of fascioliasis are becoming more common, according to the WHO website on neglected tropical diseases.  Transmission is apparently by ingestion of watercress or mint, although “encysted larvae may be found on other salad vegetables.”

 

[6] From the U.K. National Animal Disease Information Service [Nadis.org.uk]

 

[7] My sheaf of research papers on Galba worldwide fills an entire drawer of my filing cabinet.  For an opening into the vast literature, you might start with:

• The Lymnaeidae 2012: Fossarine Football [7Aug12]
• The American Galba and The French Connection [7June21]
• Exactly 3ish American Galba [6July21]
• What Lymnaea (Galba) schirazensis is not, might be, and most certainly is [3Aug21]

[8] For a review of the bulimoides/cubensis confusion, see:

• What is Lymnaea bulimoides? [13Feb24]

[9] For a review of the bulimoides/cockerelli confusion, see:

• Lymnaea (Galba) cockerelli, Number 15. [12Mar24]

[10] Greg R. Foster’s contributions:

• Foster, G.R. (1971)  Winter vagility of the aquatic snail Lymnaea (Galba) bulimoides Lea.  Basteria 35: 63 – 72.
• Foster, G.R. (1973) Soil type and habitat of the aquatic snail Lymnaea (Galba) bulimoides Lea during the dry season Basteria 37: 41 – 46.

[11] No, not really.  I’m straining to create some sort of drama out of parking by a weedy ditch in a rented Acura.  Work with me here.

 

[12] Well OK, the water was cool, and there was a little bit of current.  Melanoides populations can reach great densities in such ditches down in Florida [13].  But the point I’m trying to make is that pleurocerid gastropods do not live in such environments, under any circumstance, period.

 

[13] And Pomacea too, if you want to quibble.  Ditches are different in Florida.  See halfway through my essay:

• The Mystery Snail Color Genetics Project [6June23]

[14] I would have identified this population as Juga hemphilli, but opening the 2022 revision by Strong and colleagues [15] it appears that hemphilli has been synonymized under Juga plicifera.  I really need to dig into that paper.  Perhaps in a future post.

 

[15] Strong, Ellen E., J.T. Garner, P.D. Johnson, and N. V. Whelan (2022) A systematic revision of the genus Juga from fresh waters of the Pacific Northwest, USA (Cerithioidea, Semisulcospiridae).  European Journal of Taxonomy 848: 1 – 97.

 

[16] In the Columbia Slough Natural Area (E) I recorded Cipangopaludina chinensis, Physa acuta, Helisoma trivolvis, Lymnaea auricularia, and Gyraulus parvus.  At Kelly Ck (F) just Physa acuta.  At the Clackamas River (G) I recorded Juga plicifera, Fluminicola virens, and Physa acuta.

 

[17]  045.1666690, -123.3129760, to be quite precise.

 

[18] Throughout the day, my long-suffering wife had been chauffeuring me around NW Oregon like a poodle and patiently waiting for me in the car, reading a book, with the motor running and the AC on.  At some point during my lengthy explorations at the Gahr Farm, a public-spirited citizen stopped to warn her about the hazards of parking a car at idle over a grass stubblefield as dry as Farmer Gahr’s.  She cut the engine immediately, of course.  But was a bit on the cranky side when I eventually returned.