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.

 

Taxonomy of the Pleurocera laqueata/troostiana complex. Part II, Ly - Z. Or, Just 974 Starfish Left to Go.

Editors note – This is the fifth (and final) installment of a series I started way back in September of 2024, starring Pleurocera laqueata with P. troostiana and P. simplex in supporting roles.  If you have a serious interest in the evolution and systematics of the North American Pleuroceridae, you might want to go down to footnote [1] and refresh your memory of previous episodes before proceeding.  If you are not interested in pleurocerid snails, on the other hand, I cannot imagine how the essay that follows could be much more than an irritation.

We opened last month’s essay with a tally of the pleurocerid nomina that Calvin Goodrich [2] recognized as valid to describe representatives of his Groups of Goniobasis catenaria and Goniobasis laqueata in the Ohio, Cumberland, and Tennessee River systems.  We observed that there  are 25 such names and reviewed the first 12 of them (alphabetically), promising to finish the job this month.

I did not mention it at the time, because it is a bit embarrassing, but I have found one Latin nomen useful for certain pleurocerid populations of the greater Ohio River basin that Goodrich synonymized under something else, and hence was not listed by him in 1940.  So, the total is actually 26 names, and we have 14 to review today.  Sorry – I know that’s going in the wrong direction, and I apologize.

Lyonii.  Isaac Lea [3] described Goniobasis lyonii in brief Latinate form from “Grayson County, Kentucky” in 1862.  Goodrich [2, 4] synonymized lyonii under Goniobasis laqueata and the nomen was carried passively (with a long list of other junior synonyms) into his Group of Goniobasis laqueata.  From there it disappeared, not mentioned at all by Burch [5], forgotten and consigned to the boneyard.

We consider the nomen lyonii valid and useful at the subspecific level [6], Pleurocera troostiana lyonii (Lea 1862), identifying laqueata/troostiana hybrids at the western and northern limits of the phenomenon. For our rationale, together with a copy of Lea’s [7] original figure and a modern topotype, see Dillon [8] pp 81 – 88 or my essay of [6July20].  An image of the holotype (USNM119147) is collected below.

USNM119147 (23.1 mm), MCZ53965 (17.3),
USNM118923 (13.6), USNM118429 (20.1)

Nassula. Timothy Abbot Conrad [9] described Melania nassula in 1834 from “the limestone spring at Tuscumbia, Alabama.”  Goodrich [2, 4] considered that the taxon named a distinct and valid species in his Group of Goniobasis catenaria; Burch followed suit in his Elimia catenaria Group.

No original type material seems to have survived, according to Graf [10], although the MCZ holds the “possible syntype” figured above (MCZ 53965).  And a pleurocerid population matching Conrad’s original 1834 description and figure (#9 below) quite well still inhabits the Tuscumbia Big Spring to the present day.  It does, indeed, look very much like an Atlantic drainage (or Floridian) population of Pleurocera catenaria has been airlifted 300 miles west and dropped into North Alabama.  This is a distinct and valid biological species, Pleurocera nassula (Conrad 1834).

Paupercula.  Isaac Lea described Goniobasis paupercula in brief Latinate form in 1862 [3], giving the type locality as “North Alabama, Prof. Tuomey,” with a more complete English description and figure following in 1863 [7].  Goodrich [2,4] recognized it as a valid species in his “Group of Goniobasis laqueata,” as did Burch [5] in his “Elimia laqueata group.”

We consider the nomen a junior synonym of Pleurocera troostiana perstriata (Lea 1853) [11], identifying laqueata/troostiana hybrids with decollate shells in North Alabama.  For our rationale, together with a copy of Lea’s [7] original figure and images of two topotypes (an adult and a juvenile, both R), see Dillon [8] pp 61 – 71 or my essay of [10May20].   An image of the holotype (USNM 118923) is collected above.

Perstriata. Isaac Lea [11] described Melania perstriata from “Coosa River, Alabama, Prof. Brumby, Huntsville, Tenn., Mr. J. Clark” in 1853.  Goodrich [2, 4] recognized it as a valid species in his “Group of Goniobasis laqueata,” restricting its type locality to the Big Spring at Huntsville, Alabama.  Burch [5] concurred on the specific value of the nomen but transferred it to his “Elimia catenaria group.”  We consider the nomen valid at the subspecific level, Pleurocera troostiana perstriata, identifying laqueata/troostiana hybrids with little or no costation on the body whorl.

For our rationale, together with a copy of Lea’s [11] original figure, an image of a modern topotypic specimen, and example shells from several additional populations, see Dillon [8] pp 51 – 59 or my essay of [15Apr20].  An image of the holotype (USNM 118429) is collected above.

From Conrad [9], Lea [16], Lea [7]

Plicata-striata.  Albert G. Wetherby’s [12] 1876 description of Goniobasis plicta-striata [13] is very difficult to obtain today.  But Walker [14] quotes his type locality as “Stone River and Mill Creek, Rutherford County, and Sinking Creek, Shelbyville, TN.”  Goodrich [2] assigned the nomen to his Group of Goniobasis laqueata.  Burch re-spelled the nomen without the dash and shifted it to his Elimia catenaria group. 

The entire main stem of the Stones River is impounded today, as is Mill Creek, but Sinking Creek is inhabited by apparently healthy populations of both P. laqueata and P. troostiana edgariana, not especially helpful for our understanding of Wetherby's taxon today.  

Fortunately, Wetherby donated N = 65 paratypes “ex original lot” to Harvard’s Museum of Comparative Zoology (MCZ 149453).  Unfortunately, that entire lot of shells is dead collected, worn, and bleached – the poorest excuse for type material I have ever seen preserved in any collection, in my entire 50 years of professional experience. 

I have some insight into the origin of this problem, although I cannot explain it.  Several years ago I myself was quite stricken by a gigantic bed of relic pleurocerid shells at the bottom of Bradley Creek, a tributary of the East Fork Stones River near Lascassas.  The photo below, taken through about an inch of gently flowing water, shows thousands of P. laqueata shells, primarily, with scattered troostiana hybrids, all in various stages of decomposition.  Why Albert G. Wetherby would paw through such a bed, select 65 and describe them as “Goniobasis plicata-striata” is beyond me.

An obliging curatorial assistant at Harvard's MCZ [15] selected two shells from lot 149453 as exemplars to photograph for their online catalog at my request, offering seven images of the two shells from various angles. The best of those seven images is reproduced down below.  From some angles, it is possible to make out, just barely, weak plications on the top half of the shell I have figured.  I cannot find evidence any striation on either exemplar shell at any angle photographed.

Therefore, Goniobasis plicata-striata (Wetherby 1876) appears to be a simple junior synonym of Pleurocera laqueata laqueata (Say 1829) [28].

Bradley Creek, TN

Porrecta.  Isaac Lea [16] described Goniobasis porrecta in brief Latinate form from “Gap Creek and Spring” (Cumberland Gap, TN) in 1863, with more complete English description and figure (#47 above) in 1866 [17].  Goodrich [2] considered it a valid species in his “Group of Goniobasis catenaria,” subsuming vittatella (Lea 1863) under it, as did Burch [5] in his “Elimia catenaria group.”

We consider the nomen a junior synonym of Pleurocera troostiana troostiana (Lea 1838).  For our rationale, together with an image of a modern topotype, see Dillon [8] pp 1 – 7 or my essay of [4Aug19].  An image of the holotype (USNM 118834) is collected below.

Pybasii.  Isaac Lea [3] published a brief Latinate description of Goniobasis pybasii from “Tuscumbia, Alabama” in 1862, with English description and figure following in 1863 [7].  This is the third of Lea’s 1862/63 “eighty-two new species” of Goniobasis we have reviewed in the present essay, along with lyonii and paupercula, all synonyms of the same species.  A nineteenth-century malacological hat trick!  There will be two more.

Goodrich [2, 4] recognized pybasii as a valid species in his “Group of Goniobasis laqueata,” as did Burch [5] in his “Elimia laqueata group.”  We consider the nomen a junior synonym of Pleurocera troostiana perstriata (Lea 1853), identifying laqueata/troostiana hybrid populations in North Alabama.  For our rationale, together with a copy of Lea’s [7] original figure and an image of a modern topotypic specimen (Q), see Dillon [8] pp 61 – 71 or my essay of [10May20].   An image of the holotype (USNM 119329) is collected below.

MCZ149453 (16.1 mm), USNM118834 (17.7 mm),
USNM119329 (19.8 mm), USNM119296 (16.9 mm)

Rubella.  This is the fourth of the “eighty-two new species” that Isaac Lea [3] described in 1862 we have reviewed this afternoon.  Lea’s original figure [7] is reproduced above (#191), as well as a fresh image of the holotype (USNM 119296).

Goodrich [2] considered rubella a valid species in his “Group of Goniobasis catenaria,” noting as he did, however, that the species was “reported originally from Cherokee County, North Carolina, and not found there since.  May be the same as porrecta.”  Burch [5] did not list rubella but did reproduce Tryon’s figure of it (#369), with the caption “E. rubella = ?E. porrecta.”

Right.  Lea’s original description, “very near to Melania (Goniobasis) teres but differs in being carinate,” together with his figure and type specimen, make it quite clear that Goniobasis rubella, like porrecta and like teres, is a simple junior synonym of Pleurocera troostiana troostiana (Lea 1838).

That said, I really think that the type locality given by Lea for his G. rubella, “Near Murphy, Cherokee County, North Carolina,” must have been in error.  The modern range of P. troostiana does not extend any further east up the Hiwassee drainage than Polk County, TN.

Spinella.  The fifth of Isaac Lea’s 1862/63 creations [3, 7] we have reviewed this month, Goniobasis spinella was described from “Sycamore, Claiborne County, Tennessee” as “very nearly of the same outline of Melania (Goniobasis) strigosa but much smaller, slimmer, and darker color.”  Goodrich [2] considered the nomen a subspecies of Goniobasis arachnoidea in his “Group of Goniobasis catenaria,” as did Burch [5] in his “Elimia catenaria group.”

Lea’s original figure is reproduced way down below (#130), and his holotype (USNM 119269) freshly imaged immediately below.  We consider spinella another simple junior synonym of Pleurocera troostiana troostiana (Lea 1838).  For our rationale, together with an image of a modern topotype, see Dillon [8] pp 41 – 49 or my essay of [7Jan20].

USNM119269 (16.3 mm), USNM118448 (14.2 mm),
USNM121603 (19.4 mm)

Striatula.  Isaac Lea [18] described Melania “striata” in brief Latinate form from “Tennessee” in 1841, with English description and figure following in 1843 [19].  He amended the name to “striatula” in the interim [20].  Goodrich [2] considered striatula a valid species in his “Group of Goniobasis catenaria,” as did Burch [5] in his “Elimia catenaria group.”

Lea’s original [19] figure (#49) is reproduced below, and a shell catalogued into the USNM collection as the holotype (USNM 118448), that Graf [10] referred to as a “possible syntype” is imaged above.  They do not match.  Rats.

Lea’s original figure showed strong striation and no plication, looking like a synonym of typical P. troostiana troostiana, as I myself suggested in Dillon [8] pp 41 – 49 and in my essay of [7Jan20].  The nominal holotype, however, shows plicae as strong as striae [21], looking very much like P. troostiana edgariana.  And the locality information, simply “Tennessee,” is no help resolving the discrepancy.

Turning to the letter of Lea’s [18] original description as a tiebreaker, we read “shell striate” to lead off, with no mention of plication.  But in Lea’s remarks, we read “In some individuals the folds are numerous – in others the striae predominate and cover nearly all the whorls.”  Are the “folds” plicae?

In the end, I suppose it does not matter.  Melania striatula (Lea 1842) is a junior synonym of Pleurocera troostiana (Lea 1838), but whether of the purebred (typical) form or the hybrid edgariana form, I don’t think we’ll ever know.

Strigosa. Another of Isaac Lea’s 1841/43 classics [18,19], Melania strigosa was described as “somewhat like the teres herein described” from “Tennessee, Dr. Troost, Holston River Dr. Warder.”  Goodrich [2] considered it a valid species in his “Group of Goniobasis catenaria,” as did Burch [5] in his “Elimia catenaria group.”

In my 2023 essay [8, pp 41 - 49], and in the 2020 blog post from which that essay was crafted [7Jan20], I offered four reasons to restrict the strigosa type locality to Little Flat Creek 10 miles north of Knoxville, figured a topotype, and reproduced Lea’s [19] original figure.  Lea’s holotype (USNM 121603) is imaged above.  We consider the nomen yet another simple junior synonym of Pleurocera troostiana troostiana (Lea 1838).

From Lea [7], Lea [19], Lea [22]

Teres.  And a third time.  Isaac Lea [18] described Melania teres from “Tennessee, Dr. Troost” in 1841, following with a more complete English description and figure in 1843 [19].  Again, Goodrich [2] considered it a valid species in his “Group of Goniobasis catenaria,” as did Burch [5] in his “Elimia catenaria group.”

We considered the locality data too vague to send us on a modern day teres-hunt for our blog post of [7Jan20] or the essay [8, pp 41 - 49] derived from it, but did reproduce both Lea’s [19] original figure, and figure #356 from Burch [5].  An image of Lea’s holotype (USNM 119251) is collected below.  We consider the nomen yet another simple junior synonym of Pleurocera troostiana troostiana (Lea 1838).  So, it materializes that Isaac Lea scored malacological hat tricks in both 1841 and in 1862.  Without question, Isaac Lea was the greatest of all time, of something.

Torta/tortum.  Isaac Lea’s brief, Latinate description of Melania torta from “Big Creek, Lawrence County, Tennessee” was published in 1845 [22], with more complete English description and figure following in 1848 [23].  Tryon [24] assigned the nomen to Pleurocera in 1873, changing the spelling to tortum [25].  Goodrich considered tortum a valid subspecies of Goniobasis laqueata, as did Burch, of Elimia laqueata.

Lea’s original [23] figure is reproduced above (#30), and a fresh image of the holotype (USNM 119255) collected below.  Quoting him verbatim:

“There were eight specimens of this species submitted to my examination by Mr. Clark, of Cincinnati.  […] The apices of the individuals now before me are slightly eroded … one of the specimens has small folds near the apex, with decussating striae. […] The body whorl is very long.”

Lea’s description, original figure, and designated holotype all strongly suggest that Melania torta is a laqueata/simplex hybrid, making the nomen a junior synonym of populations we designated Pleurocera laqueata castanea (Lea 1841) in our essay of [12Nov24].

Lawrence County, Tennessee, is on the Alabama line just north of Florence in the Shoal Creek subdrainage.  I cannot find a “Big Creek” anywhere on modern maps, but Pleurocera laqueata populations bearing shells of typical morphology are widespread in that county.  And the FWGNA database contains five records of P. laqueata castanea in Lauderdale County, AL, just south.

USNM119251 (21.6 mm), USNM119255 (18.0 mm),
USNM119256 (25.3 mm)

Troostiana.  Isaac Lea [26] described Melania troostiana from “Mossy Creek, Jefferson County, Ten” in 1838, quite early in his career.  Goodrich [2] considered it a valid species in his Group of Goniobasis catenaria, as did Burch [5] in his Elimia catenaria group.

Pleurocera troostiana is the oldest name for a distinct, valid, biological species of pleurocerid snail widespread in small streams of the greater Ohio drainage from SW Virginia through most of Tennessee, North Alabama and Southern Kentucky.  For a complete review, illustrated with a copy of Lea’s [26] original figure and images of modern topotypes, see Dillon [8] pp 35 – 40 or my essay of [9Dec19].  An image of the holotype (USNM 119256) is collected above.

I provided a photo of a living P. troostiana individual in my follow-up essay of [7Jan20], published in Dillon [8] pp 41 – 40.  I then developed the argument that a great variety of pleurocerid nomina in East Tennessee might be junior synonyms, including arachnoidea, porrecta, spinella, strigosa, striatula, and teres, as reviewed above.

Then in a series of four essays posted on this blog between April and July of 2020, and published in 2023 by Dillon [8] pp 51 – 88, I recognized three subspecies [6] of P. troostiana inhabiting the waters of North Alabama, Middle Tennessee, and Kentucky: perstriata (Lea 1853), edgariana (Lea 1841), and lyonii (Lea 1862), synonymizing a large number of additional nomina underneath them.  I also published a separate circular [27] reviewing the entire four-subspecies system, including the typical (s.s.) form.

So, we closed last month’s essay with a reference to the sanctimonious story usually entitled “Starfish on the Beach,” which seems to have evolved from a 1969 essay by Loren Eiseley.  Including the 12 starfish we dispatched last time, our two-month total is 26 starfish on the beach, 7 of which we tossed back into the sea.  At the species level we recognize laqueata, troostiana, and nassula.  At the subspecies level, all of hybrid origin, we recognize perstriata, edgariana, and lyonii under troostiana and castanea under laqueata.  The other 19 starfish we have now bagged for the dumpster.  Just 974 starfish left to go.

Postscript:

On 10Feb25 this essay was combined with four companion pieces and published as a pdf separate entitled, "Systematic review of the Pleurocera laqueata/troostiana complex."  That document is available for download as FWGNA Circular No. 8.

Notes:

[1] Here are the four essays on the Pleurocera laqueata/troostiana complex that preceded the present:

• The type locality of Melania laqueata [18Sept24]
• Widespread hybridization between Pleurocera laqueata and P. troostiana in streams of the Tennessee/Cumberland [15Oct24]
• Reticulate evolution in the North American Pleuroceridae [12Nov24]
• The taxonomy of the Pleurocera laqueata/troostiana complex.  Part I, A – La. [10Dec24]

[2] Goodrich, C. (1940) The Pleuroceridae of the Ohio River drainage system.  Occasional Papers of the Museum of Zoology, University of Michigan  417: 1-21.

[3] Lea, Isaac (1862) Description of a new genus (Goniobasis) of the Family Melanidae and eighty-two new species. Proceedings of the Academy of Natural Science of Philadelphia 14: 262 – 272.

[4] Goodrich, C. (1930)  Goniobases of the vicinity of Muscle Shoals.  Occasional Papers of the Museum of Zoology, University of Michigan 209: 1 – 25.

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

[6] Subspecies are populations of the same species in different geographic locations, with one or more distinguishing traits.  For more, see:

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

[7] Lea, Isaac (1863) New Melanidae of the United States.  Journal of the Academy of Natural Sciences of Philadelphia (New Series) 5: 217 – 356.

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

[9] Conrad, T. A. (1834) New Fresh Water Shells of the United States, with coloured illustrations, and a monograph of the genus Anculotus of Say; also A synopsis of the American naiades.  Philadelphia, Judah Dobson.  76 pp, 8 plates.

[10] Graf, D. L. (2001) The cleansing of the Augean stables.  Walkerana 12(27): 1 - 124.

[11] Lea, Isaac (1853)  Description of a new genus (Basistoma) of the Family Melaniana, together with some new species of American Melaniae.  Transactions of the American Philosophical Society (new series) 10: 295 – 302.

[12] We first met Albert G. Wetherby (1833 – 1902), author of the baffling taxon Helisoma duryi, back in 2020:

• The flat-topped Helisoma of The Everglades [5Oct20]

[13] Wetherby, A.G. (1876) Remarks on the variation in form of the family Strepomatidae, with descriptions of news species  Proceedings of the Cincinnati Society of Natural History 1:10.

[14] Walker, B. (1918)  A synopsis of the classification of the freshwater Mollusca of North America, North of Mexico, and a catalogue of the more recently described species, with notes.  Univ. Mich. Mus. Zool. Misc. Publ. 6: 1 - 213.

[15] The assistance of Ms. Melissa Merkel, curatorial assistant in the Malacology Department at Harvard's Museum of Comparative Zoology, is gratefully acknowledged.

[16] Lea, Isaac (1863) Descriptions of fourteen new species of Melanidae and one Paludina.  Proceedings of the Academy of Natural Sciences of Philadelphia 15: 154 – 156.

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

[18] Lea, Isaac (1841) Continuation of Mr. Lea's paper on New Fresh Water and Land Shells.  Proceedings of the American Philosophical Society 2: 11 – 15.

[19] Lea, Isaac (1843) Description of New Fresh Water and Land Shells.  Transactions of the American Philosophical Society (New Series)  8: 163 – 250.

[20] Lea, Isaac (1842) Minutes of the Stated Meeting of December 2.  Proceedings of the American Philosophical Society 2: 237.

[21] If you are confused about striation and plication (costation), see my 2020 essay for a diagram:

• Huntsville Hunt [15Apr20]

[22] Lea, Isaac (1845) Descriptions of new fresh water and land shells.  Proceedings of the American Philosophical Society 4: 162 – 168.

[23] Lea, Isaac (1848)  Description of new fresh water and land shells.  Transactions of the American Philosophical Society 10: 67 – 101.

[24] Tryon, G. W. (1873) Land and Freshwater shells of North America Part IV, Strepomatidae.  Smithsonian Miscellaneous Collections 253: 1 - 435.

[25] At the risk of confusing the situation further.  Isaac Lea also described a Trypanostoma tortum in 1862 from the Uchee River (Creek), a tributary of the Chattahoochee on the GA/AL border.  That one was renamed Pleurocera parkerii by Tryon.

[26] Lea, Isaac (1838-39) Description of New Freshwater and Land Shells.  Transactions of the American Philosophical Society (New Series) 6: 1 – 154.

[27] Dillon, R.T., Jr.  (2020) The four subspecies of Pleurocera troostiana (Lea 1838), with synonymy.  FWGNA Circular 2: 1 - 5. [pdf]

[28] In the original version of this blog, as posted 14Jan25, I ventured to hypothesize that Weatherby’s plicata-striata was a junior synonym of Pleurocera troostiana edgariana (Lea 1841).  That was before I saw the MCZ paratypes.  On 10Feb25, I changed my mind.