Dr. Rob Dillon, Coordinator

Tuesday, December 6, 2022

In the Footsteps of the Comte de Castelnau

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023c)  In the Footsteps of the Comte de Castelnau.  Pp 287 – 296 in The Freshwater Gastropods of North America Volume 7, Collected in Turn One, and Other EssaysFWGNA Project, Charleston, SC.

Way back in September of 2020 I concluded a mundane essay about juvenile shell morphology with the following deceptively difficult question: “What, exactly, are Helisoma scalare and Helisoma duryi?

Over the four months and five essays that followed [1], we were able to establish that both taxa are big Floridian planorbids, sometimes assigned to the genus “Planorbella” for no reason whatsoever [9Sept20], set aside in a subgenus Seminolina by Henry Pilsbry [2] in 1934 [3Dec20].  The difference between the two nominal species lies in the shell coiling, Helisoma scalare being distinguished by a peculiar flat-topped “scalariform” morphology.  Helisoma duryi, on the other hand, usually bears shells of the typical planispiral type, so typical, in fact, that they are often very difficult to distinguish from those borne by dirt-common Helisoma trivolvis populations widespread across the rest of North America [5Jan21].

Ultimately, however, I only answered half of the question I posed in September of 2020.  Across the six total essays I posted on the subject, I spent 50% of my time obsessing about Helisoma duryi, focusing especially on their protean variability in shell morphology, “short, fat, tall, skinny, and all over the place” [5Jan21].  Then I spent 30% of my time obsessing about Helisoma trivolvis and 20% of my time obsessing about Henry Pilsbry [26Jan21], never really touching on Helisoma scalare at all.  So, this month let’s back up and get a fresh start at the scalare half of the question, shall we?

P. scalaris, holotype [4]
John Clarkson Jay (1808 – 1891) was the grandson of Founding Father John Jay, the first chief justice of the United States and co-author of The Federalist Papers.  I gather that by the 19th century the Jay family had acquired substantial means.  John Clarkson was trained as a physician, but apparently had enough liquid capital and leisure time to amass what was reputedly “the most complete and valuable collection of shells in the United States.”  He published catalogues of his shell collection in several editions 1835 – 1852, to which he appended “descriptions of new or rare species.”  And it was in John Clarkson Jay’s third edition of 1839 [3] that the world was first introduced to “Paludina scalaris, Nobis.  Habitat, Everglades of Florida.”  After a one-sentence description of the shell, Jay wrote, “It was presented to me by Count Castelneau.”

Jay’s holotype (AMNH 56111) is still held by the American Museum of Natural History today [4], looking just as dramatically flat-topped as Jay figured it in 1839.  Jay’s nomen “scalaris” or scalare [5] is the sixth oldest nomen applied to any of the large [6] North American planorbids, after trivolvis, glabratus [7], campanulata, corpulentum and anceps.

But if there is one lesson I have learned over my many months, indeed years, of struggling with the taxonomy of Florida freshwater gastropods, it is that “The Everglades” is a big place.  In our essay of [5Oct20] we learned that the Everglades Ecoregion, as formally defined by the Feds, extends over all or part of 18 South Florida counties, some 7,800 square miles.  And in our essay of [3Dec20] we learned that when Charles Dury told Albert Wetherby that he collected a sample of planorbids in “The Everglades of Florida” in 1879, he meant in Volusia County, a couple hundred miles north of anyplace that the Feds would call Everglades today.  What was “The Everglades” to a French Count in 1839?

Fortunately, Henry Pilsbry left us a very helpful clue in 1934, just as he did with Wetherby’s duryi.  Quoting the Elderly Emperor verbatim [2]:

“Jay's locality was ‘Everglades of Florida, presented to me by Count Castelneau;’ that is, le Comte Franqois (or Francis) de Castelnau, who travelled in the southeastern states in the thirties and early forties. He published several papers in Bull. de la Soc. de Giographie, 1839-1842, in the last (vol. 18, p. 252) alluding to his work on Florida, which I have been unable to find in Philadelphia libraries. Probably the type locality can be recovered by looking up Castelnau's itinerary in this book.”

So here in the 21st century, Count Castelnau’s papers [8] are much easier to get hold of than they were in 1934.  And even better, in 1948 a University of Florida historian named Arthur R. Seymour translated Castelnau’s work into English and republished it in The Florida Historical Quarterly [9].  And it materializes that when Castelnau said “The Everglades,” he meant the Florida panhandle, somewhere around Tallahassee.

Castlenau left Charleston, my hometown, in mid-November 1837, travelling first by rail to Augusta, then on “a very narrow and detestable road” through the heart of Georgia.  His most interesting adventure southbound took place in the “ramshackle” [10] village of Bainbridge, where “about one hundred Chattahoutchi Indians, who are allies of the whites, arrived bringing with them about sixty hostile Creeks or Muscogis.”  The Count was invited to join the Chattahoutchis for “an entire night of dancing, drinking and shouting.”

The Count arrived in Tallahassee after two weeks on the trail, exploring about the vicinity until mid-March of 1838, leaving us vivid accounts (and not a few interesting illustrations) of the small town and its environs, before returning to Charleston by way of steamer up the Apalachicola/ Chattahoochee River.  But alas, at no time in any of his writings did he address the most important subject, the snails he encountered along the way.

And so it came to pass that in February of 2021 I pointed my trusty [11] Mazda pickup south on I-95, Arthur Seymour’s translation of Castelnau’s travelogue on the passenger seat, outward bound on yet another planorbid-themed adventure.  My plan was to visit every body of water mentioned by The Count in his Florida explorations, or at least representatives thereof, searching for a topotypic population of Helisoma scalare (Jay 1839).  In the account that follows, I have interleaved quotes from Castelnau’s travels with notes from my own fieldbook.

We passed over the Oclockone [Ochlockonee] River and the Little River whose banks are delightful, then finding again pine woods we reached in the evening Tallahassee, the end of our [outbound] trip.

The Ochlockonee is what I would call (from my Carolina Lowcountry perspective) a typical blackwater river.  I launched my kayak at the boat ramp under the US90 bridge (A) and paddled upstream around the bend and could find very little habitat for freshwater gastropods of any sort – no submerged or floating vegetation, indeed almost no vegetation at the margins.

Numerous springs exist in the neighborhood and from one of them comes a pretty stream of water that after having wound around the eastern part of the city [Tallahassee] runs into the forest and forms a charming waterfall about sixteen feet high; it runs then into a ravine hollowed out of limestone and disappears underground quarter of a mile farther.

It is not uncommon in this part of the world for cities to have been founded around notable springs.  Huntsville and Tuscumbia, Alabama, come to mind in this regard.  In both of those cases, city fathers have set aside parkland in the heart of the modern city and added all manner of improvements to the springs, sometimes (in some cases, maybe) preserving some ghost of the native macrobenthos in the process.  Alas, the greatest disappointment of my fieldtrip came early, as I arrived at Tallahassee’s midtown “Cascades Park” (B).

Cascades Park

The montage above shows the modern park, with Castelnau’s original 1837 figure in the upper right corner.  Notice the landscaping beds around the modern spring run, specifically designed to discourage park visitors from approaching the water.  Little signs have been placed at the front of those beds, warning us (and our pets) not to enter the “stormwater.”  And alas, that is indeed a stormwater sewer at red arrow in photo below, the water emanating from which bears a dark, suspiciously-olive color.  I spent about 10 – 15 minutes poking around the water in desultory manner, picking up Physa, and moved on.

To the east of this town extend the lands offered by the government of the United States to General Lafayette in which is a pretty lake that bears his name. No words can convey the beauty of these sheets of water which scattered in great numbers in the midst of virgin forests in Middle Florida; they are filled with fish of many sorts and their surface is everywhere enlivened by clouds of aquatic birds, above which flies constantly the bald eagle. Among the denizens of these lakes we must mention the soft shelled turtles, as well as the alligators that are abundant there; these last reach ordinarily length of twelve feet, and although little to be feared, by their repulsive aspect they inspire terror in persons not accustomed to seeing them.

The Federal Government did indeed grant the Marquis de Lafayette a 36-square-mile tract east of Tallahassee in 1824, in gratitude for his military service to our young republic.  Lafayette never visited, however, and the entire grant had been sold off piecemeal by 1855.  The Lake Lafayette to which Castelnau referred was divided into three sections with dikes, its central section dredged for recreational use, and given the odd name “Piney Z” Lake, in honor of a nearby plantation.

Lower Lake Lafayette

I visited both the central Piney Z Lake (C) and Lower Lake Lafayette (D) at the town of Chaires.  The former was warm and trashy, and hosted but Physa and Pomacea maculata.  I had great hope for the latter, however, which I found to be a Lake in Name Only (“LINO”), choked with aquatic vegetation of all sorts.  Indeed, I enjoyed one of my prettiest paddles in recent memory, spoiled only by the thunderstorm evident on the horizon of the photo above.  And the malacofauna, which comprised nothing but Physa and Pomacea, again.

Lake Jackson is situated a league and a half [north] from Tallahassee. According to the Indians, its water gushed forth suddenly from under the ground, covering a vast cultivated plain. It is certain that trees are still to be seen there, and that when the water is low Indian trails may be noticed.

The hydraulics of Lake Jackson are indeed strange.  The water level appeared at least ten feet below bank full on the morning I visited at site (E), boat ramps high and dry.  I asked a local angler if this little patch of Florida might be suffering a drought, even as rainstorms daily drenched the remainder of the Sunshine State, coast to coast.  He replied in the negative, explaining that the Lake has a small “closed basin,” and had gone entirely dry on several occasions in his lifetime.  I thought (to myself) that a closed basin might rather lead one to expect high water in times as diluvian as those we were currently experiencing.

Lake Munson
In light of this intelligence, I suppose my readership will not be surprised to learn that the malacofauna of Lake Jackson depauperate.  In addition to the trash Pomacea I did find exactly N = 1 juvenile Helisoma.  Which I hoped, upon my departure, that I would not be forced to return and augment.

A great number of lakes or ponds are scattered to the south of Tallahassee. All these lakes are surrounded by dense woods, which are scattered some fine cotton and sugar plantations. Most of them seem to be sinking leaving on their shores a great deal of fertile land. are often almost entirely covered with rushes and plants. In their water are found great numbers water serpents (mocassins), soft-shelled turtles, gators, among which swim large flocks of aquatic their shores are crowded with bands of deer and many white headed eagles soar over them or the oaks and the immense magnolias that are shores.

Lake Munson is a good representative of a “lake scattered to the south of Tallahassee.”  I paddled around its west edge to no effect.  But at the outlet dam (F), I was pleased to discover a healthy population of Helisoma.  I was simultaneously disappointed, however, by the typical, planispiral shells they bore upon their backs.  None, alas, demonstrated the “scalariform” shell morphology that made John Clarkson Jay’s Paludina scalaris so distinctive.

As the sun set on a long, wet day touring the diverse rivers, springs, lakes and ponds of Tallahassee and vicinity, I admit to experiencing a bit of frustration.  True, I had found a couple scrappy populations of Helisoma.  But none bore shells even remotely matching Jay’s 1839 type specimen in the collection of the American Museum way up in New York City.  Were my hopes to be blighted?  Stay tuned!

Lake Munson at the outlet


[1] Here is my complete series on Helisoma duryi and the flat-topped Helisoma of Florida to date:

  • Juvenile Helisoma [9Sept20]
  • The flat-topped Helisoma of The Everglades [5Oct20]
  • Foolish things with Helisoma duryi [9Nov20]
  • The emperor speaks [3Dec20]
  • Collected in turn one [5Jan21]
  • Dr. Henry A. Pilsbry was a jackass [26Jan21]

[2] Pilsbry, H. A. (1934)  Review of the Planorbidae of Florida, with notes on other members of the family.  Proceedings of the Academy of Natural Sciences of Philadelphia 86: 29 – 66.

[3] Jay, J.C. (1839)  A catalogue of the shells, arranged according to the Lamarckian system; together with descriptions of rare species, contained in the collection of John C. Jay, M.D.  Third Edition.  Wiley & Putnam, New York.

[4] I thank Ms. Lily Berniker of the AMNH for her prompt and courteous attention to my request for this photograph.

[5] Pilsbry [2] re-spelled Jay's (feminine) scalaris to the neuter scalare to agree with the gender of the neuter noun construct Helisoma.  I thank my good buddy Harry Lee for this insight.

[6] Pilsbry divided all the North American Planorbidae into two subsections, the large ones and the not-large ones [5].  John Clarkson Jay’s scalaris is the sixth oldest name for a large one.  There are also five older names for not-large North American planorbids, which do not concern us here, but for the record: parvus, deflectus, crista, armigera, and exacuous.

[7] Thomas Say gave the type locality for his (1818) Planorbis glabratus as “Charleston, South Carolina.”  Pilsbry questioned that locality, but I believe it.  We'll come back to this subject in a couple months.

[8] Here are the originals:

  • Castelnau, F. (1839) Note sur la Source de la Rivière de Wakulla dans la Floride. Bulletin de la Société de Géographie 11 (2): 242 – 247.
  • Castelnau, F. (1842) Vues et Souvenirs de l’Amérique du Nord. Paris.
  • Castelnau, F. (1842) Note de deux Itinéraries de Charleston à Tallahassée.  Bulletin de la Société de Géographie 18 (2): 241 – 259.
  • Castelnau, F. (1843) Essai sur la Floride du Milieu.  Nouvelles Annales des Voyages et des Sciences Géographiques 110, 4: 129 – 208.

[9] And here are the translations:

  • Castelnau, F., A.R. Seymour and M.F. Boyd (1948) Essay on Middle Florida, 1837 – 1838.  The Florida Historical Quarterly 26(3): 199 – 255.
  • Seymour, A.R. and F. Castelnau (1948) Comte de Castelnau in Middle Florida, 1837 – 1838.  Notes concerning two itineraries from Charleston to Tallahassee.  The Florida Historical Quarterly 26(4): 300 -324.

[10] “Here I was able to form an idea of the character of the people of this region, by noticing the ramshackle condition of the ordinary houses, all the windows of which were broken and the doors broken down.  I asked the cause of it and I learned that a few days before all of the inhabitants having got drunk and committed this havoc.”

[11] Five of those letters, anyway.

Thursday, November 3, 2022

The SNHTHICACBW Marstonia 6: pachyta

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023b)  The SNHTHICACBW Marstonia IV: pachyta.  Pp 253 – 260 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other EssaysFWGNA Project, Charleston, SC.

Last time we reviewed the minor hydrobioid taxon Marstonia from its origin as a subgenus in 1926 through its 1977 promotion by Fred Thompson, its 1994 death at the hands of Bob Hershler, and its 2002 resurrection by the dynamic duo of Thompson and Hershler working together.  And we focused on a subset of Marstonia that Thompson called, “small narrow hydrobiids that have in common a carinate body whorl,” abbreviated “SNHTHICACBW.”  This subset includes M. letsoni from way up north, which we reviewed in [19Jan16] and [5Feb16], and which in retrospect, might have been numbered 1 and 2 in this series.  And the subset also includes M. ozarkensis, which we reviewed in [10Feb20] and [16Mar20], which in retrospect might have been numbered SNHTHICACBW installments 3 and 4.

Then after laying all that groundwork, which took almost 700 words, which is approaching my target length for an entire essay, I blathered on another 1,400 words about the original member of the SNHTHICACBW group, Marstonia scalariformis.  We focused especially on the ACBW part of the formula, “a carinate body whorl,” dwelling at length on the variability that carination can demonstrate.  And at the eagerly anticipated end of last month’s essay, we concluded that the ranges of these little hydrobiids can be vast.  The range of M. scalariformis seems to extend from Illinois to Alabama.  And that they are obscure.  You will not find a population of SNHTHICACBW Marstonia unless you look sharp and employ special techniques.

So, when last we left our intrepid malacologist, he was standing knee-deep in the Flint River at Cherrytree, Alabama, washing stones into a sawed-off trash can (Site CT on the map way down below).  He was indeed finding Marstonia scalariformis.  But that was not all.

The four hydrobioids of the Flint River

There are four hydrobioids inhabiting the dark recesses of rocks and organic debris at Cherrytree, as figured above.  The Marstonia scalariformis we beat to death last month.  We’ll feature the lithoglyphid Somatogyrus populations in a pair of essays to be posted later this winter.  Maybe we’ll come back to Marstonia arga at some time further in the future [1].  What is that fourth hydrobiid?   What is Marstonia pachyta?

About three paragraphs into the first 700 words of blather I published last month I mentioned that when Thompson [2] initially elevated Marstonia to the genus level in 1977 he described five new species.  Among these was a snail “known to occur only in Limestone Creek and Piney Creek, Limestone County, Alabama” that “is readily identified by characteristics of both its verge (penis) and shell.”  That new species was a not-especially-small, not-particularly-narrow hydrobiid without a notably-carinate body whorl that he called Marstonia pachyta.

Thompson figured the M. pachyta penis as demonstrating a typical spatulate or bladelike form featuring three glandular areas, which I have labelled using Bob Hershler’s system as a pair of terminal glands (Tg) and a ventral gland (Vg) in the figure below.  (Thompson also figured another M. pachyta penis missing a second Tg. Bookmark that for later.)  Bob Hershler [3] came behind Thompson in 1994 and re-drew the essentially identical figure I have reproduced in the bottom half of the figure as well.

M. pachyta penis [4]
Regarding the shell morphology of his Marstonia pachyta, Thompson described the shape as “ovate conical,” and gave the adult length as ranging 3.3 – 4.0 mm.  The little sample figured below came from the type locality in Limestone Creek, east of Mooresville, AL (marked MV on the map way down below).

And regarding the range.  Although at the 1977 writing of his description Thompson was only aware of M. pachyta populations in Limestone and Piney Creeks, on 15Aug2000 he collected a sample from Bradford Creek at Martin Road [5] about 7 miles east (marked MR below), and on 16Aug2000 he collected a sample from Round Island Creek at Nuclear Plant Road [6], about 10 miles west (marked NP below).

From Bradford Creek it is just 18 miles further east to the Flint River, on the other side of Huntsville.  But here is yet another peculiar lapse in the long, strange career of Fred Thompson.  As far as I can tell, Thompson only spent one, single day collecting in the entire 500 square mile Flint River subdrainage, during which time he never recorded a single hydrobioid.  The freshwater gastropod collection of the FLMNH holds exactly N = 17 lots collected by Fred Thompson from anywhere in the Flint River or its tributaries, from seven sites he visited on Saturday, 27Sept69.  Among these lots are 16 of pleurocerids and 1 of Laevapex fuscus.  Zero hydrobiids of any species [8].

For comparison, Thompson collected 90 freshwater gastropod lots (48 hydrobiids) from Limestone Creek over his long career.  He then seems to have travelled 25 miles west to the Flint, crossed it barely wetting a boot toe, travelled another 10 miles further west, and collected 39 freshwater gastropod lots (8 hydrobiids) from the Paint Rock River.  Does it seem a bit irresponsible to make statements of the form “known to occur only in Limestone Creek and Piney Creek” when you haven’t even looked in the (biologically very similar) Flint River 25 miles away?  I don’t know.  I’ve probably done the same sort of thing myself.

Marstonia pachyta from Limestone Ck, AL

All of which brings us back, yet a third time, to yours truly standing knee-deep in the Flint River at Cherrytree, AL (site CT).  As my readership most certainly will have been able to divine by this point, what I was finding in the bottom of my sawed-off trash can was important.  Yes, a population of M. pachyta does inhabit the Flint River, matching the shell and penial morphology of the Limestone Creek type population in all respects.  And most of the shells are indeed “ovate-conical” as described by Thompson in 1977.  They are a bit smaller-bodied, however, and some of them are beginning to show a little bit of carination on the body whorl.  Yes, you heard me right.  They are beginning to look like SNHTHICACBW Marstonia.

Ten miles east of the Flint, the next south-draining tributary of the Tennessee River deep enough to wet your mule is the Paint Rock River.  It was from the Paint Rock 0.7 mi east of Cedar Point (CP) that Fred Thompson in 2005 described a new SNHTHICACBW species, Marstonia angulobasis [9].  Thompson distinguished his M. angulobasis by its shell of “minute size” (adulthood only 2.5 mm SL), bearing flattened whorls bordered at the periphery by a distinct angle or cord.  He characterized the penis as bearing “a terminal small apocrine gland.”  That’s what Hershler would have called a “terminal gland” and abbreviated “Tg.”

Tennessee drainages of North Alabama

So about seven paragraphs above, I asked you to “bookmark” the tidbit that Fred Thompson also “figured one M. pachyta penis missing a second Tg.”  The dorsal and ventral aspects of that pachyta penis (his Figs 13C and 13D) are reproduced in the top half of the figure below, compared to his figure of the penis of M. angulobasis below.  And let me ask you a rhetorical question.  If the M. pachyta penis can have 2Tg+1Vg, or 1Tg+1Vg, could it also have 1Tg+0Vg [10]?

Regarding the shell morphology of the Marstonia population inhabiting the Paint Rock River, see figures A and B below.  Thompson collected his type lot on a canoe trip, at a spot not readily accessible.  But he also listed “other specimens examined” from Butler Mill, about 2 miles downstream.  My observations at Butler Mill (BM) suggest a Marstonia population bearing shells quite variable in their “distinct angle or cord,” or carination, or keel, or whatever anybody would like to call it.  Some of them (like B below) show one, and some of them (like A below) do not.

In my September post [7Sept22] I went to great lengths to demonstrate that the distribution of glands on the Marstonia penis shows a great deal of intrapopulation variability.  And in last month’s post [4Oct22] I went to great lengths to demonstrate intrapopulation variation in the shell carination.  The weight of the evidence before us does not suggest that Thompson’s M. angulobasis is specifically distinct from his M. pachyta.

pachyta & angulobasis [11]

But let us save Thompson’s nomen “angulobasis” at the subspecific level, shall we?  Let us henceforth refer to populations of M. pachyta bearing carinate body whorls as “Marstonia pachyta angulobasis Thompson 2005."  And let us remember, as we do, that the FWGNA Project has adopted the definition of that term as it has been understood since the birth of the modern synthesis, “populations of the same species in different geographic locations, with one or more distinguishing traits,” which means exactly what it says, neither more nor less [12].

Now let me go back and pick up those other themes from last month’s post, that business about SNHTHICACBW Marstonia being widespread and obscure.  Although it will always be difficult for field biologists to find populations of such obscure little creatures looking for them, one might not be surprised to find them pop up in quantitative macrobenthic samples.

Over the last few years, I have been blessed to develop a professional relationship Ms. Debbie Arnwine, Ms. Patricia Alicea, and Ms. Carrie Perry of the Tennessee DWR in Nashville who, in the course of their routine duties, collect and sort huge numbers of quantitative macrobenthic samples collected from all over the Volunteer State.  These they hold for some years, but ultimately discard.

Sorting through hundreds of old samples released to us by the TNDEC-DWR, Bob Winters and I have discovered SNHTHICACBW hydrobiids identifiable as Marstonia pachyta angulobasis in three tributaries of the Cumberland River, perhaps 100 miles north of the North Alabama focus of the present essay: Smith Fork of the Caney System (C, below), the West Fork Stones River south of Nashville (D, below) and in Spring Creek of the Red River system almost to the Kentucky line (unfigured).  In fact, it seems possible to us that a single, enigmatic SNHTHICACBW Marstonia shell recovered by our colleague Ryan Evans from the bank of the Elkhorn Creek north of Frankfort, KY, might represent M. pachyta angulobasis, rather than M. letsoni as we have tentatively identified it [13].

A,B = Paint Rock River, C = Smith Fork, D = W.Fk. Stones River

So now has come the time to sum up, over all six of the essays I have contributed on the SNHTHICACBW Marstonia.  In 1977 Fred Thompson recognized a group he called, “small narrow hydrobiids that have in common a carinate body whorl,” comprising four specific nomina: scalariformis, letsoni, wabashensis, and ozarkensis.  Since that date wabashensis has been synonymized, while pachyta and angulobasis added.

Populations identified by two of those specific nomina, scalariformis and pachyta, demonstrate reproductive isolation where the co-occur in the Flint River at Cherrytree, Alabama.  Their shells are distinctive, those of the former bearing a strong carination extending higher than the body whorl, those of the latter occasionally bearing weak carination on the body whorl only.  Their penial morphology is also distinctive, that of scalariformis quite slender, that of pachyta bladelike.  These are two good biological species.

Evidence presented here suggests that angulobasis is a subspecies of pachyta.  The data on penial morphology we reviewed back in 2016 suggests that letsoni has affinities with scalariformis.  The evidence we reviewed in 2020 was too fragmentary to offer any hypothesis whatsoever on ozarkensis.

And finally.  All of these tiny little snails are widespread and obscure.  Their ranges can extend over many, many states.  They are not endemic to anywhere; they are epidemic everywhere across most of the eastern interior.  Populations come, and populations go.  You cannot find them.  Opening my thesaurus and dumping it wholesale onto the computer screen flickering before you, the SNHTHICACBW Marstonia are shadowy, secretive, enigmatic, mysterious, and obscure.


[1] Thompson [2] described Marstonia arga from Guntersville Reservoir in 1977, but it has since spread up the impounded Tennessee to the vicinity of Knoxville, and throughout the impounded Cumberland River as well.  It’s an evolutionary winner!  Seems unfair to ding the TVA for extincting some species without crediting them for carp, kudzu, and M. arga, doesn’t it?

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

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

[4] Above, Marstonia pachyta penis modified from Thompson [2] figure 13A and 13B.  Below, Marstonia pachyta penis from Hershler [3] figure 53a.  Dorsal on left, ventral on right. Tg = terminal glands, Vg = ventral gland, P = penial filament.

[5] FLMNH catalog 279921, collected by FGT on 8/15/2000 from Bradford Creek at Martin Road, 2 miles south of Madison, AL.

[6] FLMNH 279628, collected by FGT on 8/16/2000 from Round Island Creek at County Road 25, 3 miles west of Jones Crossroads, AL.  Haggerty & Garner [7] were not able to confirm this record in their exhaustive survey of 2008, however.

[7] Haggerty, T.M. & J.T. Garner (2008)  Distribution of the armored snail (Marstonia pachyta) and slender Campeloma (Campeloma decampi) in Limestone, Piney, and Round Island Creeks, Alabama.  Southeastern Naturalist 7: 729 – 736.

[8] And in fact, the entire Flint River (AL) catalog at the FLMNH is a disappointment.  Just N = 50 freshwater gastropod records total from all collectors, the 33 lots not collected by Thompson undated and obviously ancient.

[9] Thompson, F.G. (2005)  Two new species of hydrobiid snails of the genus Marstonia from Alabama and Georgia.  The Veliger 47: 175 – 182.

[10] Yes.

[11] Above, Marstonia pachyta penis modified from Thompson [2] figure 13C and 13D.  Below, Marstonia angulobasis penis from Thompson [9] figure 18a and 18b. Dorsal on left, ventral on right. Tg = terminal gland, Vg = ventral gland, P = penial filament.

[12] For more on the subspecies concept as applied by the FWGNA Project, see:

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

[13] For more about that single, enigmatic SNHTHICACBW shell from Kentucky, see:

  • Is Marstonia ozarkensis extinct? [16Mar20]

Tuesday, October 4, 2022

The SNHTHICACBW Marstonia 5: scalariformis

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023b)  The SNHTHICACBW Marstonia III: scalariformis.  Pp 243 – 252 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other EssaysFWGNA Project, Charleston, SC.

Our modern understanding of the North American hydrobiid genus Marstonia is entirely to the credit of two men, as similar as they were different, Dr. Fred Thompson and Dr. Bob Hershler.  I featured the former colleague, who passed away five years ago, in a pair of essays posted on this blog in 2017 [15Feb17] [14Mar17].  I profiled the latter colleague, now retired, in an essay I published in July [5July22].  And to appreciate their contributions to our understanding of the most enigmatic group of gastropods inhabiting the fresh waters of the American East, let’s back up and get a running start at it.

F. C. Baker [1] described the subgenus Marstonia in 1926 to distinguish Henry Pilsbry’s familiar and widespread Amnicola lustrica [2] from Thomas Say's equally familiar and widespread Amnicola limosaBaker made this distinction on the basis of shell and radula, taking no notice of penial morphology at the time.  He recognized seven species in his new subgenus Marstonia inhabiting the lakes of Wisconsin, all of which would either be synonymized under lustrica, or subsequently split out to Lyogyrus, leaving his subgenus Marstonia effectively monotypic.

M. scalariformis, Cherrytree, AL

It was Fred Thompson who, in his seminal 1977 monograph [3], raised Marstonia to the genus level, highlighting a distinction that Berry [4] had made in the penial morphologies of limosa and lustrica.  Thompson included three previously described species in Marstonia: Pilsbry’s (1890) lustrica, Pilsbry’s (1895) olivacea [5] and his own (1969) agarhecta.  To this short list he added five new species: arga, castor, halcyon, pachyta, and ogmorhaphe [6].  This eight-species model of Marstonia was the understanding brought down from the mountain by Jack Burch in 1982 [7].

In his 1977 closing remarks on “species of questionable status,” however, Thompson suggested that four species “currently placed in Pyrgulopsis [8]” might “actually belong in Marstonia.”  Here he listed scalariformis (Wolf 1869), letsoni (Walker 1901), wabashensis (Hinkley 1908) and ozarkensis (Hinkley 1915), noting “these are Small Narrow Hydrobiids That Have In Common A Carinate Body Whorl.”  Let us henceforth refer to this subgroup as the “SNHTHICACBW” Marstonia.

The broad-brush similarity in penial morphology between his eight newly minted Marstonia species and those four SNHTHICACBW species, which since 1886 had been allocated to Pyrgulopsis, seems to have worked on Thompson’s mind, however.  And I speculate that a rising young star in the constellation of hydrobioid systematics also had something to do with it, as well.  Because in 1987 the dynamic duo of Bob Hershler and Fred Thompson united to synonymize Baker’s Marstonia under Call & Pilsbry’s Pyrgulopsis [9].

The next advance in the inexorable march of tiny-snail science came in 1994, with Bob Hershler’s masterful “Review of the North American Freshwater Snail Genus Pyrgulopsis[10].  As we mentioned back in July, my buddy Bob counted 54 “Western American Species” and 11 “Eastern American Species” in that work, including Fred Thompson’s original eight plus three of Thompson’s SNHTHICACBW: letsoni, ozarkensis and scalariformis.

Marstonia penis morphology [10]
And a mere eight years later, as if to validate their dynamic credentials before the Judgement Seat of Malacology Eternal, the duo of Thompson and Hershler [11] resurrected Marstonia back to full genus level on the basis of female reproductive anatomy [12], reallocating Hershler’s list of 11 eastern species into it once again, plus comalensis of Pilsbry & Ferriss 1906.

The systematic status of the SNHTHICACBW hydrobioids was the dasher in 76 years of taxonomic churn.  We have previously featured two elements of this enigmatic group in a pair of essays each, reviewing the mighty efforts of previous workers to understand the tangled evolutionary relationships among them.  In [19Jan16] and [5Feb16] we reviewed the situation with Marstonia letsoni, and in [10Feb20] and [16Mar20] we covered Marstonia ozarkensis.  For the remainder of this essay, which has actually turned out to be the fifth installment of a series I did not know I was starting back in 2016, we will focus on the original member of the group, M. scalariformis, together with its synonyms and forms.

Pyrgula scalariformis was described by Wolf (1869) from a single empty shell collected along the Illinois River in Tazewell County, Illinois [13].  And the original rationale that Call & Pilsbry offered for their description of the new genus, Pyrgulopsis, back in 1886 was to contain scalariformis and their own virtually-identical species from the Illinois bank of the Mississippi river at Rock Island, P. mississippiensis [8].  Hershler [10] considered both mississippiensis and wabashensis (Hinkley 1908) synonyms of scalariformis, the latter described from the Wabash River in Indiana, perhaps 200 miles southeast.  All three nominal species have been considered extinct from their type localities by multiple authorities.  Hershler made his anatomical observations from a population collected in the Meramec River of Missouri, perhaps 200 miles south of Wolf’s type locality.

Hershler’s [10] figure 53b showed an overall penial morphology really quite different from the peculiar blade-shaped structure mounted by the western Pyrgulopsis we beat to death last month, or indeed typical eastern Marstonia such as M. lustrica, which we figured back on [5Feb16].  The M. scalariformis penis actually looks like a penis, with a prominent hose-shaped pointy-thing and a single reduced gland sticking out the side, which Hershler simply called a “terminal gland.”  It is very reminiscent of the penis of the SNHTHICACBW Marstonia letsoni that E. G. Berry [4] figured from up in Michigan, which we also reprinted in our essay of [5Feb16].  I’ve pasted Hershler’s figure 52e of the letsoni penis next to his 53b of the scalariformis above, to refresh your memory.  The only difference seems to be a larger terminal gland in letsoni.

Turning now to the shell morphology.  Some significant fraction of Hershler’s Missouri sample did indeed bear shells every bit as “scalariform” as Wolf’s type specimen from Illinois.  This is the ACBW predicate of Thompson’s SNHTHICACBW, which Hershler called a “peripheral keel.”  But that carination or keel varied “from weak to well-developed.”  And strangely, although Hinkley’s [14] description of P. wabashensis emphasized the absence of a carination/keel, Hershler’s reexamination of Hinkley’s Indiana type material also revealed that “many of the paratypes from the type locality (the Wabash) are carinate and very closely resemble some scalariformis.”

Shimek's P. mississippiensis [15]

The situation with the other scalariformis synonym, Call & Pilsbry’s mississippiensis, is identical.  In 1892 the University of Iowa Professor Bohumil Shimek [15] published an excellent paper in an obscure journal [16] exhaustively cataloguing shell variation in “more than 1500” subfossil SNHTHICACBW collected from Pilsbry’s type locality on the bank of the Mississippi River.  Quoting Shimek verbatim:

“The series is an unbroken one, the species varying from the ecarinate forms which are scarcely angled at the periphery of the body-whorl, and in which the suture is not impressed, to forms in which the carina is elevated and extends quite to the apex, and in which the suture is deeply impressed.”

Importantly, three different early-twentieth century authors reported SNHTHICACBW species identified as either mississippiensis or scalariformis from Shoal Creek, a tributary of the Tennessee River in North Alabama.  The initial collection, identified as Pyrgula mississippiensis, was made by Hinkley and confirmed by Bryant Walker [17].  F. C. Baker [18] dissected a fresh sample he identified as Pygrulopsis scalariformis from Shoal Creek, figuring shell, operculum, and radula, agreeing with Shimek that mississippiensis should be synonymized underneath it.  Baker did not offer us any anatomical data on his Shoal Creek sample, alas.

The special importance of this record, which I cannot find any reason to doubt, is that it extends the range of scalariformis 500 km south from Indiana into drainages of the Southern Interior.  But alack, the same fate seems to have befallen the Shoal Creek population as has been suffered by Wolf’s original scalariformis, Pilsbry’s mississippiensis, and Hinkley’s wabashensis.  Repeated efforts by Thompson and Hershler failed to rediscover any living specimens.  Shoal Creek is today inhabited by a similar species better adapted to trashy, lentic environments, Marstonia arga.

All of which brings us to the present day, and the first person.  Many have been the sleepless nights I have passed in recent years, combing through the yellowed pages of dusty journals, preparing for the expansion of the FWGNA Project through the Tennessee drainages of North Alabama [19].  And many have been the Latin binomina assigned to the hydrobioid fauna of those rich waters.  And many have been the hours I have waded in the shallows of Shoal Creek, wiping rocks in a sawed-off trashcan, hunting for M. scalariformis in the drainage of The Tennessee. To no avail.

The SNHTHICACBW Marstonia are really, really hard to find.  At an AMU meeting many years ago I asked Fred Thompson how he did it.  And seven of the twelve words he ever spoke to me were these: “I wash rocks in a white bucket.”

Washing vegetation into a white bucket

I have personally found the walls of standard pickle-dimension buckets too deep to effectively inspect and recover little 3 mm items from the bottom of.  So, a few years ago I bought a white kitchen trashcan from the Walmart and sawed it off at about six inches deep, yielding a vessel that is more like a very-deep tray.  And I pull rocks up from the rapids – especially rocks covered with Podostemum or bryophytes – and wipe them off into the vessel.  I also target larger items of organic debris – sticks and so forth, and the stems of emergent vegetation.  And then I slosh the bottom mess around and slide it off like I was panning for gold, which in the malacological world, I suppose I am.

I have found this technique effective for surveying the diverse hydrobioid fauna of North Alabama, about which we will have much more to say in coming months.  But as for Marstonia scalariformis in Shoal Creek – goose egg, bagel, O-fer.

Ah, but!  Not all of the reference materials to which I have turned these sleepless nights have been yellowed tomes.  Reference to the Global Biodiversity Information Facility [20] returns 62 records of Marstonia (or Pyrgulopsis) scalariformis (or mississippiensis) held in national collections, 16 of which are from North Alabama.  Almost all of those 16 records are old, historic lots from Shoal Creek.  But late one night I was pleased to find in a GBIF data download [21] three recent records of Marstonia scalariformis (1 USNM, 2 NCSM) collected by Jeff Garner, working in the Flint River just east of Huntsville, about 70 miles east of Shoal Creek.

And with that intelligence on a clipboard riding on the passenger seat of my little Mazda pickup, in 2021 I was indeed able to confirm a population of Marstonia scalariformis deep in the bryophytes and periphyton covering the rocks in rapids of the Flint River at Cherrytree, AL.  Witness the figure that opened this essay, way up above.

To summarize.  The essay you have just suffered through, discursive as it most certainly has been, has nevertheless managed to touch three points.  First, the ranges of SNHTHICACBW Marstonia can be vast.  The straight-line distance from the bank of the Mississippi River at Rock Island, Illinois, to the shoals of the Flint River at Cherrytree, Alabama is 900 km.  Second, populations of M. scalariformis can vary strikingly in their shell morphology, especially with regard to carination.  And third, those doggone things are tough to find.  Populations come, and populations go.  It is hard to imagine how an itinerant malacologist, such as yours truly, might find a Marstonia scalariformis population anywhere, ever, unless he is consciously looking for one.  Special techniques are required.

Or alternatively, I suppose, biologists who are NOT looking for them might turn them up in quantitative macrobenthic samples, perhaps?  In any case.  The SNHTHICACBW Marstonia are, in three words, widespread, polymorphic, and obscure.  Carry those three words forward, and we’ll see you all next month.


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

[2] Of course, a freshwater gastropod as common and widespread as what we identify today as Marstonia lustrica was well known before Pilsbry described it (or re-described it) in 1890.  The taxonomic situation was complicated by uncertainty over the identity of Thomas Say’s (1821) Paludina lustrica.  See:

  • Baker, H. B. (1960)  Lustrica (Paludina) Say, 1821 (Gastropoda): Proposed suppression under the plenary powers.  Z.N.(S.) 730.  Bulletin of Zoological Nomenclature 18: 146 – 148.

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

[4] Berry, E. G. (1943) The Amnicolidae of Michigan: distribution, taxonomy and ecology.  Miscellaneous Publications of the Museum of Zoology, University of Michigan 57: 1 – 68.

[5]  Thompson considered Pilsbry’s M. olivacea “of uncertain status and probably extinct.”  We will have much more to say about this in a future post.

[6] Thompson spelled the specific nomen with two pees, “ogmorphaphe” at the heading of his 1977 description, but just the single pee “ogmorhaphe” enough times subsequently to make the one-pee spelling stick.

[7] 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 a stand-alone volume in 1989 (Malacological Publications, Hamburg, MI).

[8] Call R. E. & Pilsbry H. A. (1886). On Pyrgulopsis, a new genus of rissoid mollusk, with description of two new forms. Proceedings Davenport Academy of Natural Sciences 5: 9-14.

[9] Hershler, R., and F.G. Thompson (1987)  North American Hydrobiidae (Gastropoda: Rissoacea): redescription and systematic relationships of Tryonia Stimpson, 1865 and Pyrgulopsis Call and Pilsbry, 1886. The Nautilus 101:25-32.

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

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

[12] The occurrence of a large extension of the albumen gland into the pallial roof is a unique Marstonia characteristic [10].  Molecular phylogenetic analyses have also supported the distinction between Marstonia and Pyrgulopsis, and the retention of both genera in the Hydrobiidae sensu strictu.  See:

  • Hershler,R., Liu,H.-P. and Thompson,F.G. (2003) Phylogenetic relationships of North American nymphophiline gastropods based on mitochondrial DNA sequences.  Zool. Scr. 32 (4): 357-366.
  • Liu, H., and R. Hershler (2005)  Molecular systematics and radiation of western North American nympholine gastropods. Molecular Phylogenetics and Evolution 34: 284-298.
  • Wilke T., Haase M., Hershler R., Liu H-P., Misof B., Ponder W. (2013)  Pushing short DNA fragments to the limit: Phylogenetic relationships of “hydrobioid” gastropods (Caenogastropoda: Rissooidea).  Molec. Phyl. Evol. 66: 715 – 736.

[13] Wolf, J. (1869)  Descriptions of three new species of shells.  American Journal of Conchology 5: 198.

[14] Hinkley, A. A. 1908. A new species of Pyrgulopsis. Nautilus 21: 117-118.

[15] Bohumil Shimek (1861 – 1937) should be better known in the malacological community today than he is.  Variously listed as a botanist, a zoologist, a geologist, a conservationist, and an engineer, he published widely in a variety of disciplines, including quite a few papers in The Nautilus 1888 – 1936.  There’s a photo of him on his Wikipedia page, if you are curious.

[16] I cannot help but think that, if Shimek’s conclusion had supported the validity of Pilsbry’s P. mississippiensis, this paper would have been published in The Nautilus:

  • Shimek, B. (1892) Pyrgulopsis scalariformis (Wolf) Call and Pilsbry.  Bulletin from the Laboratories of Natural History of the State University of Iowa 2: 168 – 174.

[17] Hinkley, AA (1906) Some shells of Mississippi and Alabama. Nautilus, 20:40-44.  Walker B (1906) New and little known species of Amnicolidae. Nautilus, 19:114-117.

[18] Baker, F.C. (1928) Freshwater Mollusca of Wisconsin, Part I, Gastropoda. Bull. Wisc. Geol. Natur. Hist. Survey, no. 70.  Madison: University of Wisconsin Press.  Baker simply wrote (pg 138) , “Animal: Not examined or described as far as known.”  Why my hero F. C. Baker didn’t seize the opportunity to describe the penial morphology of the fresh sample of M. scalariformis before him, I cannot say.  I admit that I am a bit disappointed.  With page 138, anyway.

[19] Grand opening announced this spring:

  • Freshwater Gastropods of the Tennessee/Cumberland [16May22]

[20] I could just as easily have referred to the IDigBio database and obtained the same results, I feel sure.  I don’t know why I chose GBIF over IDigBio.  See:

  • 20 Years of Progress in the Museums [22May19]

[21] Here is my direct download from GBIF, accessed 10Feb22.  Extract and open the text file called “occurrence” in excel, tab delimited:  https://doi.org/10.15468/dl.mqfb8b

Wednesday, September 7, 2022

Just 125 species of Pyrgulopsis in the American West

Editor’s Notes - If you are looking for something citable, the gray-literature report upon which the following essay is based can be downloaded as FWGNA Circular #6 from footnote [1] below.  This essay was subsequently published as: Dillon, R.T., Jr. (2023b)  Just 125 species of Pyrgulopsis in the American West.  Pp 233 – 242 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other EssaysFWGNA Project, Charleston, SC.

In July [6July22] we reviewed the career of the USNM-Smithsonian’s Dr. Robert Hershler, for over 30 years the undisputed authority on the hydrobioid freshwater gastropods of North America.  Running our finger through the checklist that my buddy Bob published with Hsiu-Ping Liu in 2017 [2], we counted “126 species of Pyrgulopsis inhabiting the waters of the Western United States, 107 of which Bob Hershler was the author.”

Journey back with me now to a bleak Tuesday morning in May of 2020.  The ivory towers of Academia were locked and bolted, the store shelves stripped bare of toilet paper [3], the streets silent save for the rattle of wooden handcarts, and rhythmic appeals to bring out the dead.  And I opened my email inbox and found a message from Hsiu-Ping.  She asked me if I would be “interested in working on a project to determine the species status of Pyrgulopsis vinyardi and P. gibba.”  And here was my reply:

“Well, OK, maybe.  It would take me a while to get up to speed on the Western hydrobioids, and the maximum speed I could ever achieve would look like standing still, next to Bob Hershler.  But Bob’s not taking any more laps around the track, and I am.”

Thus encouraged, sort-of, Hsiu-Ping proceeded to lay out the situation.  Bob had described Pyrgulopsis gibba from the northwestern Great Basin Desert of California, Nevada, and Oregon in a relatively small paper published in 1995 [4] and followed with a description of P. vinyardi endemic to "two springs in the Squaw Valley drainage" of north-central Nevada in his big monograph of 1998 [5].  The two bore shells strikingly different in the relative size of their body whorls, and penises notably different in their morphologies as well.

Pyrgulopsis vinyardi [5] and P. gibba [4]

Regarding penial morphology, see the figure below.  I have marked the part of the penis that actually does the job, really just a simple filament, with the red letter “P.”  Everything else in Bob’s dorsal-and-ventral figures labelled P. vinyardi (boxed), and in his three dorsal-and-ventral figures labelled P. gibba, is the ridiculously enlarged and elaborate penial lobe characteristic of Pyrgulopsis. If you’re curious to see a whole mount of the actual organ itself, look back at my July post [6July22].

The distribution of glandular regions on the surface of this spatulate or blade-shaped lobe has for many years been considered diagnostic of hydrobiid species.  Bob has marked dorsal glands as “Dg,” ventral glands as “Vg” and terminal glands as “Tg.”

Bob wrote in his description of P. gibba: “This species is unique among members of the genus (as of 1995) in having penial ornament of terminal gland, Dg3, and ventral gland.”  He went on to observe, however, “Dg3 often present, either as a small papule (sometimes double) or large raised unit.”  Note the modifier, “often.”  Bob figured one P. gibba penis that had no Dg3 at all.  See the Dg3 regions encircled in red.  And in 1998 he noted that the development of the ventral gland often varies as well.

Penial morphology, modified from Hershler [6]
In his description of P. vinyardi three years later, Bob wrote, “Penial ornament a small terminal gland, large Dg1, small Dg2, small Dg3, additional dorsal gland on lobe, and large ventral gland.”  So, upon dissection, P. vinyardi males are expected to demonstrate the entire smorgasbord of glands, including everything seen on P. gibba plus Dg1 and (usually) Dg2.  He noted later, however, that Dg2 was “rarely absent.”

The obvious analogy is to “lock-and-key” reproductive isolation such as has been widely documented across the Phylum Arthropoda, except that the gastropod lock is a bag, and the gastropod key is a sock.

I'm not buyin' it!
I’m skeptical.  In the case of Physa, with which I do have a great deal of experience, even very different penial morphologies do not preclude mating [7].  There is (indeed) some prezygotic reproductive isolation between biological species of Physa, but it is behavioral (or possibly chemical) on the part of the snail mounted as female.  My personal observations do not suggest that mechanical barriers play a significant role in interspecific copulation in gastropods.

And besides.  Anybody who has walked through the weeds by a pond on a warm summer night, or hell, anybody who has a friend with a male dachshund, you all know.  Males will do it with anything.  Coke bottles.  It just does not matter.

So, both Bob’s 1995 description of P. gibba and his 1998 description of P. vinyardi were published absent any genetic data, before he met Hsiu-Ping.  Between 2003 and 2008 Bob and Hsiu-Ping did, however, publish mitochondrial CO1 gene sequences for three individual P. gibba and one P. vinyardi [9].  And it materialized that gibba and vinyardi are very similar genetically, mtDNA percent sequence divergence ranging just 0.5% to 1.1%.

All of which now brings us back up to the dark days of May 2020, and my email exchange with Hsiu-Ping.  Hsiu-Ping explained to me that she had recently agreed to provide molecular identifications for a set of 21 Pyrgulopsis samples [10] collected from northern Nevada by Ms. Diana Eck of the environmental consulting firm, Stantec.  And that she had sequenced the CO1 gene from approximately 4 – 6 individuals from each population, for a total sample size of N = 88.  The Baysian tree below shows the N = 29 unique CO1 haplotypes Hsiu-Ping discovered, with unidentified population number (“unk”), setting aside duplicates.  Also shown are the three control P. gibba sequences from GenBank, and the one control P. vinyardi.

CO1 sequence diversity in N. Nevada Pyrgulopsis

So, the second branch of the tree does indeed divide the control vinyardi from the control gibba, as one might expect.  But look at the samples from unidentified population #22, collected 23 miles NE of Lovelock, Nevada.  Sequences 22-A and 22-B cluster with vinyardi, while sequence 22-C clusters with gibba!  Could this be evidence that Spring #22 is inhabited by both P. gibba and P. vinyardi?  And that the two populations demonstrate reproductive isolation in sympatry?  My knowledge of the vast and weighty literature is far from encyclopedic, but I cannot recall any case of sympatric Pyrgulopsis species ever previously documented in the American West.

Hsiu-Ping and I resolved to test population #22 for character phase disequilibrium [11].  And so it came to pass that in June of 2020 a fresh sample of Pyrgulopsis collected from population #22 arrived on my doorstep, courtesy of Ms. Eck.  My half of the study was to dissect these snails and characterize their penial morphology as either matching P. vinyardi or matching P. gibba.  Then sending the residual tissues to Hsiu-Ping, she would characterize the individuals as either matching vinyardi or matching gibba by their CO1 gene sequence.  A significant relationship between penial morphology and CO1 sequence would suggest reproductive isolation within the sample, confirming the specific distinction between vinyardi and gibba.

Pyrgulopsis from Site 22

And so, I went to work with tiny forceps and even tinier dissecting needles, cracking and dissecting 30 adults [12], identifying 15 females and 15 males.  I ignored dg3, which is an unreliable character.  Then five males demonstrated both dg1 and dg2, matching P. vinyardi.  Three males did not demonstrate either dg1 or dg2, matching P. gibba.  And seven males demonstrated either dg1 or dg2, intermediate between gibba and vinyardi.  And in July of 2020 I forwarded 15 little tubes onward to Hsiu-Ping, 5 marked G for gibba, 3 marked V for vinyardi, and 7 marked I for intermediate.

The Baysian tree below shows Hsiu-Ping’s results for 13 of the 15 snails I dissected (setting aside 2 duplicate sequences), plus all five of the sequences she obtained from Ms. Eck’s original sample, plus the four control sequences from GenBank.  Hsiu-Ping’s analysis did resolve two sort-of distinct clusters of CO1 sequence within population #22, but those two clusters did not correspond to penial morphology, nor indeed, did they correspond especially well to the four CO1 sequences previously deposited in GenBank, three from nominal gibba and one from nominal vinyardi.  There is no pattern in the distribution of samples labelled G, V, and I.

Hence there is no evidence of character-phase disequilibrium between penial morphology and CO1 sequence in Pyrgulopsis population #22.  Hence there is no evidence of reproductive isolation between P. gibba and P. vinyardi.  The gray-literature report we filed with Ms. Eck on 22Oct21, available for download as FWGNA Circular #6 from footnote [1] below, concluded “that P. gibba and P. vinyardi should be synonymized into one species.”  My buddy Bob’s (1995) gibba would have priority over his (1998) vinyardi.

From Liu & Dillon [1]

OK, I know that’s a lot of technical detail for a silly, frivolous blog post.  So come back up to the surface with me and let’s take a big, fresh breath of air together.  Look at those two little shells I figured at the top of this essay, and then look at those four sets of penis diagrams four column inches below.  Both of the shells figured above, and all of those penises, were borne by a single biological species of Pyrgulopsis.

I should conclude this essay, however, emphasizing once again that science is the construction of testable hypotheses about the natural world.  Science is not right, it is testable.  And over the course of a distinguished career spanning almost 40 years, my buddy Bob rigorously constructed 126 testable hypotheses about the Pyrgulopsis fauna of the great American West.  One day, I feel sure, somebody will come behind him and test the 125 that remain. I cannot imagine when, or by whom.  Not it.


[1] Liu, H-P, and R. T. Dillon, Jr. (2021) Resolving the species status of Surprise Valley Pyrg (Pyrgulopsis gibba) and Vineyard Pyrg (Pyrgulopsis vinyardi).  Report to Stantec Environmental Consulting. FWGNA Circular 6: 1 – 5. [pdf]

[2] Hershler, R. & H-P. Liu (2017) Annotated Checklist of Freshwater Truncatelloidean Gastropods of the Western United States, with an Illustrated Key to the Genera.  US Bureau of Land Management Technical Note 449: 1 – 142.

[3] We always used pine cones when I was growing up, too poor for corn cobs.

[4] Hershler R. 1995. New freshwater snails of the Genus Pyrgulopsis (Rissooidea: Hydrobiidae) from California. The Veliger 38(4): 343-373.

[5] Hershler R. 1998. A systematic review of the hydrobiid snails (Gastropoda: Rissooidea) of the Great Basin, western United States. Part I. Genus Pyrgulopsis. The Veliger 41: 1-132.

[6] The boxed figure of the P. vinyardi penis was scanned from figure 39 of Hershler [5], showing dorsal aspect on the left and ventral aspect on the right.  The remainder of the figure, showing penial morphology for three different P. gibba males, was scanned from figure 12 of Hershler [4].  Again, dorsal aspect on the left, ventral on the right.  Abbreviations Dg = dorsal gland, Vg = ventral gland, Tg = terminal gland, P = penial filament.  The Dg3 region is encircled.

[7] The literature on prezygotic reproductive isolation in Physa is extensive.  Here’s a good entry:

  • Dillon, R.T., A.R. Wethington, and C. Lydeard (2011) The evolution of reproductive isolation in a simultaneous hermaphrodite, the freshwater snail Physa.  BMC Evolutionary Biology 11: 144. [html] [pdf]

[8] Penial morphology of Pyrgulopsis sadai, from Hershler [5], figure 39.

[9] The three CO1 sequences for P. gibba and the one sequence for P. vinyardi were published in four different papers:

  • Hershler, R., Frest, T.J., Liu, H.-P., Johannes, E.J. 2003a. Rissooidean snails from the Pit River basin, California. Veliger 46:275-304.
  • Hershler, R. and Liu, H.P. (2004) A molecular phylogeny of aquatic gastropods provides a new perspective on biogeographic history of the Snake River Region. Mol. Phylogenet. Evol. 32 (3), 927-937.
  • Hershler, R., Liu, H.-P. 2008. Ancient vicariance and recent dispersal of springsnails (Hydrobiidae: Pyrgulopsis) in the Death Valley system, California-Nevada. In: Reheis, M.C., Hershler, R., Miller, D.M., eds. Late Cenozoic drainage history of the southwestern Great Basin and lower Colorado River region: geologic and biotic perspectives. Geological Society of America Special Paper 439:91-101.
  • Hershler, R., Liu, H.-P. and Gustafson, D.L. (2008) A second species of Pyrgulopsis (Hydrobiidae) from the Missouri River basin, with molecular evidence supporting faunal origin through Pliocene stream capture across the northern continental divide. J. Molluscan Stud. 74 (4), 403-413.

[10] Ms. Eck actually sent 22 populations for analysis, but population #11 turned out to be a lymnaeid.  So just 21 populations of Pyrgulopsis.

[11] In January of 2022 I defined character phase disequilibrium as “any violation of independent assortment between one or more morphological characters and one or more characters of demonstrably genetic origin.”  Although CPD can arise from any violation of the assumption of random mating, the most likely explanation in Spring #22 would be reproductive isolation.  See:

  • What is character phase disequilibrium? [4Jan22]
  • Character phase disequilibrium in the Gyraulus of Europe [4Feb22]

[12] Actually I messed up a few, so no count.