Huntsville Hunt

Editor’s Notes – After a couple months of digression into other topics, today we return to phenotypic variety and taxonomic chaos in the pleurocerid fauna of the Tennessee/Cumberland.  I have written six essays in the series thus far, from August 2019 to January 2020.  But I’d especially recommend that you review my December and January posts on P. troostiana before going forward.

This essay was subsequently published as: Dillon, R.T., Jr. (2023b)  Huntsville Hunt.  Pp 51 – 59 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other Essays.  FWGNA Project, Charleston, SC.

Variation in the number and strength of shell plicae (or costae), those little scallop-shaped folds wrapped around the whorls of diverse gastropods worldwide, no different from variance in every other character of the phenotype of every other creature that walks, creeps, swims or flies on this earth, has both genetic and environmental components [1].  It is always important to remember both.

Calvin Goodrich dedicated Number III in his “Studies of the gastropod family Pleuroceridae” to the phenomenon of shell plication in 1934 [2].  He documented variation in an impressive list of 21 species of Goniobasis, including G. arachnoidea (a junior synonym of troostiana), generally correlating plicate shell sculpture with upstream/downstream environmental gradients or with broadly-regional pattern. 

Misako Urabe [3] reported evidence that the strength of the shell costation (plication) developed by sibships of Korean Semisulcospira was a function both of the phenotype of the mother and the coarseness of the substrate upon which her offspring were raised, sand promoting costation more than cobble.  Taking inspiration from the work of both Goodrich and Urabe, I have argued that populations of Pleurocera catenaria from Atlantic drainages of The Carolinas varying dramatically in their shell plication be accorded subspecific status, regardless of the origin of the trait [4].

 

Melania perstriata [8]

In any case, none of the populations of P. troostiana we discussed in January, under any synonym of that species, bore plicate/costate shells, under any synonym of that shell character.  Nor indeed, does any population of any pleurocerid species anywhere in East Tennessee demonstrate any shell plication whatsoever [5].  If you set off on a voyage down the Tennessee River from headwaters in Virginia to heart in Alabama, you would pass thousands of populations of pleurocerid snails, comprising 16 species.  But the first plications you would see on the shell of any pleurocerid waving at you as you passed would pop up around the westward bend of the river at Chattanooga, where its dip begins into North Alabama.  Those would be the easternmost populations of Pleurocera laqueata [6], a chunky-shelled inhabitant of small rivers and mid-sized streams, widespread in Middle Tennessee but strangely absent further eastward.

And for some reason – perhaps regional substrate, perhaps hybridization [7] – the pleurocerid populations bearing slender, striate shells inhabiting the smallest tributaries of the Tennessee west of Chattanooga also begin to demonstrate plication, only where their range overlaps the characteristically-plicate P. laqueata.

So in 1853 Isaac Lea described and figured a pleurocerid from Alabama which he called Melania perstriata [8].  He focused on its striate shell, acutely conical with elevated spire, drawing no distinction between his new species and any of the pleurocerid species bearing striate shells and elevated spires he had previously described in East Tennessee.  Indeed, he observed that his new perstriata was “strongly allied” to his striatula (1841/43), which we discussed in January.  Although Lea did not mention any plication on the shell of perstriata in his description, his figure (reproduced above) shows light but distinct plicae on the upper whorls.

Lea gave the habitat of his Melania perstriata as “Coosa River, Alabama, Prof. Brumby.  Huntsville, Tenn., Mr. J. Clark.”  I feel certain that Lea meant Huntsville, Alabama, not Huntsville, Tennessee, for reasons that will become obvious shortly.  Tryon [9] passed Lea’s figure and description along uncritically as “Goniobasis” perstriata.

One of Calvin Goodrich’s best least-known works was his (1930) “Goniobases of the vicinity of Muscle Shoals” [10], by which he meant North Alabama, generally.  Here are the first two sentences of that important contribution: 

“Nine species and two subspecies of Goniobasis are recognized in this paper as inhabiting the vicinity of Muscle Shoals, Alabama.  I have not had the heart to count the names it has been thought necessary to throw into synonymy, always a slough of despond in the case of the Pleuroceridae.” 

Amen, Brother Calvin!  That second sentence could summarize much of my professional career.

Goodrich began his treatment of Goniobasis perstriata with several paragraphs of detailed observations on the shell morphology of the population inhabiting Big Spring Creek in Huntsville, which he said is “apparently the type locality.”  I am confident that Goodrich was correct about this.  The “Mr. J. Clark” credited by Isaac Lea for the type collection was quite likely a gentleman named Joseph Clark, the President of Huntsville, Alabama from 1844 to 1849.  And where else would the President of Huntsville collect shells to pack off to the Eastern Scientific Establishment than the large and impressive spring around which his city was built, the historic site of one of the earliest waterworks in America?

Goodrich’s observations on the “average specimen” from Big Spring Creek [11] matched Lea’s description and figure very well, focusing on the “slender, delicate” shell with striking sculpture consisting of “low plicae crossed by strong revolving lines.  The plicae disappear on the spire and the striae continue to the base.”  But to my eye, the most intriguing of Goodrich’s observations about the Big Spring Creek population are not about the “average specimen,” but rather: 

“A study of the variation of perstriata takes one so far afield that some of the original characteristics seem altogether lost and to be replaced with new features.  In Big Spring Creek there have been taken specimens that are only microscopically striate, some that show no plicae and others that are smooth and shining upon the last whorl.” 

Ten years later, based on his observations of the North Alabama pleurocerid fauna generally, Goodrich [13] dropped Lea’s “Coosa River” suggestion and expanded Lea’s “Huntsville” suggestion to “Springs and small streams of North Alabama.”  He then recognized three subspecies, all from Alabama tributaries of the Tennessee River: the typical G. perstriata perstriata (Lea 1853), G. perstriata crispa (Lea 1862), and G. perstriata decampii (Lea 1863). 

“Elimia” perstriata was accorded “Priority 1” conservation concern in the state of Alabama by Garner and Johnson in the big 2017 review volume edited by Shelton-Nix [14].  As a locality Garner & Johnson suggested, “Extant only in a few streams in Madison and Lawrence counties.”  Yes, modern-day Huntsville does indeed sprawl across much of modern-day Madison County.

Madison Co, AL. See note [15] for locality data

So on Monday morning March 9 I launched an expedition to North Alabama, resolving to visit as broad a sample of springs, streams, and small tributaries of the Tennessee drainage across the ten-county region as practically possible, focusing especially upon the environs of Huntsville.  I had mighty good weather as a general thing, and nothing ever happened to me at all [15].

And on Tuesday and Wednesday I was able to document six populations of pleurocerids under the bridges of Madison County, Alabama [16], in both rural and urban settings, bearing shells “acutely conical with elevated spire,” varying rather strikingly in both their striation and their plication, as figured below.  The shells most closely matching Lea’s (1853) figure were indeed borne by the population inhabiting the waters of the Big Spring of Huntsville, marked (P) on the map above.

Today the Huntsville Big Spring emerges from the rocky face of a small hill in the middle of the city and runs about a half-mile through a recently-renovated park to join Pinhook Creek.  The first couple-hundred yards of the stream are somewhat green and shady; the remainder of the course is entroughed in massive concrete bulkheads, thoroughly urbanized, and infested with gigantic koi of elaborate morphology and voracious habit.  But right at the mouth of Big Spring Creek, where it cascades down to join Pinhook Creek, I found a population of pleurocerids inhabiting what I here offer as the type locality of Melania perstriata (Lea 1853).

Madison County P. troostiana populations [15]

The shells borne by the perstriata population at its type locality (P) are entirely striated, bearing light but distinct plicae that tend to become obsolete with growth.  That is generally true upstream in Pinhook Creek (V) and at Ashburn Spring south of Huntsville (Z) as well.  But the shells borne by populations in the Flint River (W) and at Burns Spring east of Huntsville (Y) are only weakly striate or plicate, on the upper whorls alone.  And in Limestone Creek (U) no striation nor plication is detectable on the shells whatsoever.  To borrow Goodrich’s poetic imagery, they were “smooth and shining upon the last whorl.”  Compare Limestone Creek shell morphology with that demonstrated by the P. troostiana population inhabiting Gap Creek, which kicked off this long series way back in August of 2019 [17].

I cannot find any biological evidence counter to the hypothesis that perstriata (Lea 1853) is a junior synonym of troostiana (Lea 1838).  But let’s save perstriata at the subspecific level to describe lightly-plicate/costate populations of Pleurocera troostiana, shall we?  Remember that we have defined the word “subspecies” to mean “populations of the same species in different geographic locations, with one or more distinguishing traits.”  Those words mean exactly what they say, nothing less and certainly nothing more [4].  The relationship between typical troostiana and its subspecies perstriata in Alabama is the same as that between typical catenaria and its subspecies dislocata in the Carolinas.  The FWGNA database will show that sites P, V, W, Y and Z are inhabited by Pleurocera troostiana perstriata, and while site U hosts typical P. troostiana troostiana.

So what about those other species that Goodrich shifted underneath perstriata, Lea’s crispa of 1862 and decampii of 1863?  Indeed, weren’t doctors, lawyers, and Indian chiefs from all over small-town America, spurred by nineteenth-century civic pride, plucking gastropods from their local springs and packing them off to the great Isaac Lea in Philadelphia?  Why yes, they were.

But storm clouds were gathering over the fertile fields of American malacology.  In our next installment... Crisis!

Notes:

[1] For an in-depth review of the heritability of shell morphology, albeit in pulmonates, see:

• The heritability of shell morphology in Physa h^2 = 0.819! [15Apr15]

[2] Goodrich, C. (1934)  Studies of the gastropod family Pleuroceridae – III.  Occasional Papers of the Museum of Zoology, University of Michigan 300: 1 – 11.

[3] Urabe, M. 2000. Phenotypic modulation by the substratum of shell sculpture in Semisulcospira reiniana (Prosobranchia: Pleuroceridae). J. Moll. Stud. 66: 53-59.  For more, see:

• Semisulcospira research: A message from The East [6Jan08]
• Semisulcospira II: A second message from The East [1Feb08]

[4] To refresh your memory on the situation with Pleurocera catenaria dislocata, and the concept of the subspecies as we use it in the FWGNA project, See:

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

[5]  Here’s a memo from the FWGNA Exception-that-Proves-the-Rule Department.  To be absolutely complete, we should note that the shells of the pleurocerid population inhabiting the Hiwassee River as it flows northwest down the mountains of East Tennessee do in fact bear dramatic costations.  This is actually a trans-Appalachian population of the Atlantic-drainage species Pleurocera catenaria.

[6] The degree of costation also varies dramatically along an upstream/downstream gradient in populations of Pleurocera laqueata as well.  See:

• Pleurocera alveare: Another case of CPP? [8Aug18]

[7] Yes, the more I study the pleurocerid populations of middle Tennessee, the more convinced I become that Pleurocera troostiana and P. laqueata hybridize.  Broadly.  Put a bookmark here, and we'll come back someday.

[8]  Melania perstriata was listed without description by Lea in 1852 (Proceedings of the American Philosophical Society Volume 5, page 252).  The species was formally described and figured the next year:

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.

[9] Tryon, G. W. (1873)  Land and Freshwater shells of North America Part IV, Strepomatidae.  Smithsonian Miscellaneous Collections 253: 1 - 435.  For more about the relationship between Lea and Tryon, see:

• Isaac Lea drives me nuts [5Nov19]

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

[11] Goodrich’s observations were based both on the extensive collections of Dr. Bryant Walker [12] and on those of the Alabama Museum of Natural History.  He especially thanked “Mrs. Herbert H. Smith who made the selection of shells of the Alabama Museum, packed and dispatched them.”

[12] Walker’s collection was donated to the University of Michigan in 1936.  For a tribute, see:

• Bryant Walker’s Sense of Fairness [9Nov12]

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

[14] Garner, J.T. & P. Johnson (2017) Freshwater Snails (Gastropods).  pp 7 – 42 in Shelton-Nix, E. (ed) Alabama Wildlife, Volume 5. The University of Alabama Press, Tuscaloosa. 355 pp.

[15] A tip of the straw hat to Huckleberry Finn, Chapter 12.

[16] Pleurocera troostiana populations in Madison County, AL:

• P = Type locality of M. perstriata. Big Spring outfall, Huntsville 34.7246, -86.5915
• U = Limestone Ck.  34.9199, -86.7645
• V = Pinhook Ck. 34.7752, -86.5915
• W = Flint R.  34.8228, -86.4832
• Y = Burns Spring  34.7696, -86.4258
• Z = Ashburn Spring  34.5249, -86.5132

[17] For a quick refresher on phenotypic plasticity in P. troostiana:

• CPP Diary: Yankees at The Gap [4Aug19]

A stultifyingly boring review...

I heard  a lot of nice comments about my online presentation to the Charleston Natural History Society Wednesday evening.  Several of you asked if the event might be available for later viewing.

Alas, it doesn't look as though my handsome face and cheery commentary were archived anywhere.  But I have uploaded a pdf version of the powerpoint presentation I offered that evening on the FWGNA site, here:

The Freshwater Gastropods of South Carolina [pdf, 6.9 mb]

Abstract:  Founded In 1998, the Freshwater Gastropods of North America Project is the largest-scale inventory of any element of the macrobenthos ever conducted in the United States. At present the survey extends over all or part of 15 states, including the Atlantic drainages from Georgia to the New York line, Ohio drainages above the mouth of the Cumberland, and Tennessee drainages above Chattanooga. For the 113 species of freshwater snails inhabiting this vast region we have developed dichotomous keys, range maps, figures, ecological notes and an overall rank-abundance tabulation.

The first state surveyed by the FWGNA Project was South Carolina. The rivers, streams, swamps, ponds and reservoirs of The Palmetto State host a fauna of 35 freshwater gastropod species, 19 prosobranchs (bearing gills) and 16 pulmonates (bearing lungs). Almost all are tiny, brown, and obscure. None are endangered, commercially important, useful in any way, or indeed even interesting. Three are exotic invasives, and another five (apparently) domestic invasives, but of no consequence. Bring clothespins for your eyelids, folks – this one’s a real snoozer.

Freshwater Gastropods Tonight!

Here’s your chance to see history in the making!  This evening at 6:30 PM (EDT) yours truly will offer the first-ever online presentation to The Charleston Natural History (Audubon) Society, “The Freshwater Gastropods of South Carolina: A stultifyingly boring review of a justifiably obscure fauna.”  This will also be the first-ever online presentation yours truly has ever offered.  What could go wrong?

The public is cordially invited!  You’ll need to download a little bit of software from the “Go To Meeting” website onto your computer, tablet, or smartphone, here:

https://global.gotomeeting.com/install/263942469

Then at 6:30, hit this link…

https://global.gotomeeting.com/join/263942469

You can also dial in using your phone, here…

United States (Toll Free): 1 877 309 2073
United States: +1 (646) 749-3129

… And in any case, enter this access code: 263-942-469.

We look forward to seeing you all this evening!

Is Marstonia ozarkensis extinct?

Editor’s Notes – This is the second of a two-part series on an enigmatic hydrobiid with a last known address in northern Arkansas.  You really should go back and read my essay of 10Feb20 before proceeding through this month’s installment, if you haven’t already.  Both essays were subsequently published together as: Dillon, R.T., Jr. (2023b)  The SNHTHICACBW Marstonia VI: ozarkensis.  Pp 261 – 268 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other Essays.  FWGNA Project, Charleston, SC.

When last we left our fearless jpeg naturalist, he had just received several images of hydrobiid snails from Ms. Rachel Vinsel, the curatorial assistant at the Illinois Natural History Survey.  One image depicted cotypic Marstonia ozarkensis, collected by A. A. Hinkley in 1914 from the White River drainage in northern Arkansas [1], declared extinct by the US Fish & Wildlife Service in late 2018 [2].  That’s the first image in the photomontage below, reprinted from last month’s essay.

Ah, but there were “several images” attached to Rachel’s late February email.  She went on to add: 

“While I have you, I was wondering if you'd mind taking a look at image 0097 as well? This one was collected in the Kishwaukee River (Rock River Dr.) Winnebago Co., IL. It's not quite 3mm tall.” 

 Rachel’s image 0097 is labelled “Kishwaukee unknown,” second from left below:

All four approx 3 mm std length

Holy crap, we have seen those little snails before.  At this point, could I ask you all to indulge me?  Would you mind opening up my essay of 19Jan16 in a new window?  Here’s the link:

A New Invasive Gastropod in the Great Lakes?

In that charmingly-befuddled essay, you may remember my fumbling with a mysterious population of 3 mm hydrobiid snails collected from the muck of Lake St. Clair, 25 miles east of Detroit.  Check out the photos in that essay, one of which has been clipped and inserted third in the montage above.  And now could I ask you to refer to my follow-up essay of 5Feb16:

Marstonia letsoni, Quite Literally Obscure.

The matches between cotypic M. ozarkensis, Rachel’s Kishwaukee unknown and the Lake St Clair Marstonia letsoni is pretty darn near perfect, am I right?  And let me add yet another observation. 

In January of 2017 I was combing through a remarkable set of collections made by our good friend Ryan Evans up in Kentucky, when my eyes fell on a single, tiny shell from Elkhorn Creek, about 10 km north of Frankfort.  That shell is depicted at the far right of the montage above [3].  That’s pretty good match as well, am I right?

So we have now established two things.  In 2016, we demonstrated that populations of Marstonia letsoni are quite literally obscure – tiny snails, inhabiting dark recesses, sometimes in deep water.  To find one, you’d need to be more persistent or more lucky than I, your humble correspondent, who has never seen one in his entire 45-year career combing the lakes and rivers of America, overtly and deliberately committing premeditated acts of freshwater malacology in the first degree.

And we have now documented that tiny, obscure hydrobiids of this general sort can have strikingly broad ranges.  Lake St Clair is 500 km north of Frankfort, KY, and 500 km east of the Kishwaukee River at Rockford, IL.  Could Marstonia letsoni range another 700 km to the Ozarks?  Might Marstonia ozarkensis (Hinkley 1915) be a junior synonym of Marstonia letsoni (Walker 1901)?

Let me make one final point in closing.  All authors who have any first-hand experience in this arcane little corner of malacology – Hinkley, Bob Hershler [4], and Shi-Kuei Wu [5] – have been unanimous that in overall morphology and life habit, both Marstonia ozarkensis and M. letsoni are very similar to a third species, Marstonia scalariformis.  The primary distinction is a carina or keel on the shell of scalariformis, which Wu and colleagues [4] observe “may be absent or only vaguely apparent” in some natural populations.  See Wu’s Figures 26 – 29 below.

M. ozarkensis (26, 27) and M. scalariformis (28, 29) from Wu [5].

Marstonia scalariformis rivals M. letsoni in both obscurity of life habit and vastness of range.  Wolf [6] described “Pyrgula” scalariformis in 1869 from a single shell found by the banks of the Illinois River.  Hinkley [7] described wabashensis from the Wabash River at the Illinois/Indiana border in 1908, which Hershler [4] synonymized under scalariformis in 1994, noting “variable carina development.”  Hershler’s figure of the penial morphology of scalariformis sampled from the Meramec River in Missouri shows bifurcation reminiscent of the letsoni penis figured by Berry [8].

And the “very incompletely known” range of scalariformis ranges all the way from central Illinois south down to tributaries of the Tennessee River in north Alabama [9].

Hinkley thought that the previously-described species most similar to his ozarkensis was wabashensis.   Hershler agreed, suggesting that wabashensis was a junior synonym of scalariformis and adding further that letsoni was also most similar to scalariformis, without directly comparing ozarkensis to letsoni.  I am not sure here today whether Marstonia ozarkensis (Hinkley 1915) is actually extinct, or if it was simply a local population of what has been called elsewhere letsoni (Walker 1901), or wabashensis (Hinkley 1908) or possibly even scalariformis (Wolf 1869), now here in the 21^st century misunderstood into oblivion.

Notes:

[1] Hinkley, A.A. (1915) New Fresh-water Shells from the Ozark Mountains. Proceedings of the United States National Museum, 49:587-589.  This is actually the 1916 volume of the PUSNM, but Hinkley’s date of publication is given as “December 23, 1915” in the index.

[2] USFWS 2018.  Ozark snail species presumed extinct following science-based surveys.

https://www.fws.gov/southeast/news/2018/12/ozark-snail-species-presumed-extinct-following-science-based-surveys/

[3] Note subsequently added: The image at far right was originally labeled "Kentucky letsoni" in my post of 2020.  After comparison with Marstonia populations in North Alabama, however, in 2022 I reidentified that little shell as Marstonia pachyta angulobasis.

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

[5] Wu, S-K, R. D. Oesch & M. E. Gordon (1997) Missouri Aquatic Snails.  Missouri Department of Conservation, Jefferson City. 97 pp.

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

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

[8] Berry, E. G. (1943)  The Amnicolidae of Michigan: Distribution, ecology, and taxonomy.  Misc. Publ. Mus. Zool. Univ. Mich. 57: 1 – 68.

[8] Walker, B. 1906. New and Little Known Species of Amnicolidae. Nautilus, 19:114-117.  Walker identified the population collected by Mr. Hinkley near Florence, Alabama, as “Pyrgulopsis mississippiensis (Pilsbry),” which is a junior synonym of M. scalariformis, according to Hershler [4]. There are also museum records of M. scalariformis from the Flint River near Huntsville that need confirmation.

Malacological Mysteries: What was Marstonia ozarkensis?

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023b)  The SNHTHICACBW Marstonia VI: ozarkensis.  Pp 261 – 268 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other Essays.  FWGNA Project, Charleston, SC.

All I know about the late Marstonia ozarkensis is what I’ve read in the newspapers.  The diminutive hydrobiid, small-bodied even by Marstonia standards, was originally described as “Pyrgulopsis ozarkensis” by A. A. Hinkley in 1915 [1] from the North Fork of the White River in north-central Arkansas, about 20 miles from the Missouri line.  Hinkley’s single-paragraph description focused entirely on the 3 mm shell (H, below), offering no anatomical observations on the animal itself, indeed no biological notes of any sort, beyond “found in shallow water on the bedrock.”

The taxon receded into utter obscurity (as opposed to mere obscurity) for 80 years, listed by Burch [2] but not figured.  Hershler [3] essentially reprinted Hinkley’s original description in his 1994 monograph with no additional observations, stating “A limited survey of this region in 1991 – 1992 did not yield this species.”  The scanning electron micrograph image of an ANSP paratype published by Hershler (a, below) was a poor likeness [4].

Marstonia ozarkensis: Hinkley [1], Hershler [3], INHS cotype.

In 1997 Wu and colleagues [5] reported the discovery of a population of P. ozarkensis in the North Fork of the White River in southern Missouri, about 45 km upstream from Hinkley’s type locality.  In 2002 Thompson & Hershler [6] resurrected the genus Marstonia and assigned Hinkley’s ozarkensis to it.  And in 2007 Christian & Hayes [7] reported a population of Marstonia ozarkensis in Mud Creek, a tributary of the Black River about 115 km east of Hinkley’s type locality.

Marstonia ozarkensis was one of the 404 “aquatic, riparian and wetland species from the Southeastern United States” listed in the megapetition filed by the Center for Biological Diversity in 2010 [8].  In response, the US Fish & Wildlife Service declared Marstonia ozarkensis “presumed extinct” in December of 2018 [9]. 

The authors of the FWS “Species Status Assessment” filed in August of 2018 [10] were unable to confirm the 1997 report of Wu and colleagues, finding that “the museum records cited for this population are not present in the museum database.”  And after some hemming and hawing about high levels of endemicity in North American hydrobioids, they concluded that the Mud Creek population “may be a morphologically similar undescribed species (D. Hayes, pers. comm.).”  Thus, to quote the 18Dec18 FWS press release [9] verbatim: 

Following rigorous, science-based surveys, the Ozark pyrg, a small snail native to Arkansas and Missouri, is presumed extinct, according to the U.S. Fish and Wildlife Service. No Ozark pyrgs have been confirmed in surveys since their first discovery in 1915. As a result of today’s finding, the pyrg will not be listed under the Endangered Species Act (ESA).

That sounds like the end of the story, doesn’t it?  For the Feds, it probably is.  But for us, not so much.

In late February of last year I was pleased to receive an email from Ms. Rachel Vinsel, the Manager for the Illinois Natural History Survey mollusk collection, with attached tif images of two hydrobiid shells collected in a wetland south of Chicago.  They were clearly Marstonia, but not of any morphology with which I was personally familiar.  So I pulled my trusty copy of Hershler (1994) out of the files and started thumbing through it, looking for clues to the identity of Rachel’s unknowns.  And my eyes were drawn to the poor likeness [4] of Marstonia ozarkensis reproduced at the top of this blog post.  Hershler’s figure looked like a possible match to the images Rachel had sent me.  And heck, it isn’t all that far from Chicago to Arkansas, is it?

But if I have learned anything from many years of misadventure as a jpeg naturalist, it is that there is no substitute for the actual specimens in hand.  And I happened to have a copy of the INHS freshwater gastropod holdings on my hard drive.  And I discovered that there are several lots of bona fide Marstonia ozarkensis in the INHS collection, collected by Hinkley himself in 1914.

So the next day I replied to Rachel, suggesting that her Chicago-area unknowns might represent a rediscovery of M. ozarkensis, but simultaneously emphasizing that she dig some of the bona fide M. ozarkensis out of the INHS collection and compare.  And on 25Feb19 she sent me a tif file depicting a really interesting series of little hydrobiids, featuring both her Chicago area unknowns and the INHS cotypic M. ozarkensis.

The “INHS” image at the far right of the photomontage that opened this essay was clipped from the photo Rachel sent me 25Feb19.  Three revelations struck me almost simultaneously.  First, and least importantly, Hershler’s figure, the only illustration I had seen to that point, didn’t look anything like bona fide M. ozarkensis.  Second, our Chicago-area unknowns didn’t look anything like bona fide M. ozarkensis either [11].  But thirdly and most importantly, the bona fide M. ozarkensis in the INHS did look a whole lot like something I had seen before.

And Rachel was not done.  There were additional tif files attached to her email of 25Feb19, including one that would challenge even that tiny little bit of knowledge I thought I might have been able to glean about the late Marstonia ozarkensis.  Tune in next time for, “Is Marstonia ozarkensis extinct?”

Notes

[1] Hinkley, A.A. (1915) New Fresh-water Shells from the Ozark Mountains. Proceedings of the United States National Museum, 49:587-589.  This is actually the 1916 volume of the PUSNM, but Hinkley’s date of publication is given as “December 23, 1915” in the index.

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

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

[4] Actually, to be fair.  It seems entirely possible to me that M. ozarkensis may have demonstrated a variety of shell form, to include the relatively robust form depicted by Hershler as well as the gracile depicted by Hinkley.  And possibly carinate forms as well, like Pyrgophorus or Potamopyrus?  Maybe even to the extreme of Marstonia scalariformis, perhaps?  But let's not get ahead of ourselves.

[5] Wu, S-K, R. D. Oesch & M. E. Gordon (1997) Missouri Aquatic Snails.  Missouri Department of Conservation, Jefferson City. 97 pp.

[6] 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.

[7] Christian A. D. & D. M. Hayes (2007) Diversity and distribution of freshwater gastropods from the Ozark region of Arkansas.  Report submitted to the Arkansas Game and Fish Commission.  34 pp.

[8] Center for Biological Diversity. 2010. Petition to list 404 aquatic, riparian and wetland species from the Southeastern United States as threatened or endangered under the Endangered Species Act.  For more, see:

• Megapetitions of the Old West [14July09]
• Megapetitions II: Armistice Day?  [18May11]

[9] The 12/2018 findings of the USFWS on Marstonia ozarkensis can be read here:

• Federal Register: Endangered and threatened wildlife and plants; 12-month findings on petitions to list 13 species as endangered or threatened species [19Dec18]
• Press Release: Ozark snail species presumed extinct following science-based surveys [18Dec18]

[10] U.S. Fish and Wildlife Service. 2018. Species status assessment report for the Ozark pyrg (Marstonia ozarkensis). 6Sept18. Atlanta, GA.  [pdf]

[11] Those two little shells of which Rachel initially sent me photos are not the subject of this essay.  I’m still not 100% sure what they were, but I think Rachel and I have settled on weirdly-fat and weirdly-dark Marstonia lustrica, and it doesn’t matter for our purposes here, anyway.

The Many Faces of Professor Troost

Editor’s notes: If you have not read last month’s post, read it.  And if you did read last month’s post, go back and read it again. The essay that follows was written under the assumption that the themes developed on 6Dec19 remain fresh in the minds of our readership.

This essay was subsequently published as: Dillon, R.T., Jr. (2023b)  CPP Diary: The Many Faces of Professor Troost.  Pp 41 – 49 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other Essays.  FWGNA Project, Charleston, SC.

Back in August we introduced the present “CPP Diary” series with an essay focusing on the Gap Creek populations of two freshwater gastropods widespread throughout the Tennessee/Cumberland [1].  In September and October, we explored the phenomenon of cryptic phenotypic plasticity (“CPP”) in one of those, Pleurocera simplex [2].  This month let’s back up and get a fresh start at that other species, shall we?

As I mentioned in August, the mission that sent me on my first visit to Gap Creek, way back in the summer of 2006, was a comprehensive VDGIF-funded survey of the pleurocerid fauna of SW Virginia.  John Robinson and I ultimately identified 83 populations of three species in our five-county study area, including 13 populations of what we were calling, at that time, “Goniobasis arachnoidea.”  We analyzed genetic polymorphism at 11 allozyme-encoding loci in 12 of our 83 populations, including three of the “arachnoidea,” reporting our results to the VDGIF in 2007 [3].

Courtesy of Chris Lukhaup

Almost all our Virginia populations of “arachnoidea” bore slender shells with small body whorls, usually striate, at least near the apex.  Shell (B) depicted second from left below, collected from Gap Creek at the TN 63 bridge, is typical.  But while genetically matching our other arachnoidea populations, the sample we analyzed from the headwaters of Gap Creek bore entirely smooth and strikingly stunted shells as shown at far left (A).  That population is so morphologically distinctive that it was described by Isaac Lea as not one but two unique species: Melania porrecta and M. vittatella [4].  This is an obvious example of CPP.

So to what population of snails, precisely, was the nomen “arachnoidea” originally intended to apply?  John G. Anthony [5] described his Melania arachnoidea in 1854 as “rather thin, spire slender and much elevated, very strongly striated and ribbed,” giving its type locality as “a small stream emptying into the Tennessee River near Loudon, Tennessee.”  This is a little city south of Knoxville, where today the Tellico Dam [6] backs up the Little Tennessee River from its mouth to Chilhowee.  

I surveyed the precincts of Loudon in the summer of 2007 and happened to sample Steekee Creek at the bridge where it enters the corporate limits (35.7242, -84.3473) on its way to The Tennessee.  There I found, in addition to P. simplex and P. gabbiana, a population of pleurocerids bearing thin shells of slender spire and strong striation such as depicted in figure (C) below. 

Goodrich [7] considered Lea’s (1862) Goniobasis spinella a subspecies of arachnoidea (Anthony 1854).  Lea [8] gave the type locality of spinella as “Sycamore, Claiborne County, Tennessee.  On maps of Claiborne county today one can find a wide place in the road marked “Sycamore Hall,” with a Little Sycamore Creek flowing freshly by just down the hill.  I collected specimen (D) depicted at far right below in May of last year, from Little Sycamore Ck at the Estes Road bridge (36.4534, -83.5076).

(A) Gap Ck upstream, (B) Gap Ck downstream, (C) Steekee Ck, (D) Sycamore Ck

But wait.  Before we plunge any further into the roaring 60’s, we really ought to paddle back about 20 years and pick up Isaac Lea’s (1841) Melania teres and M. strigosa [9].  The descriptions and figures of the two 1841 species were nearly identical to each other, as well as to arachnoidea of 1854 and spinella of 1862.  The shell of teres Lea observed was “remarkably elevated” with “spire drawn out” and “last whorl very small.”  The strigosa shell he also described as “spire drawn out,” remarking as he did that “This species is somewhat like teres herein described.”  Lea did mention “striate above” for strigosa, while not mentioning any shell ornamentation for teres.

The habitat Lea gave for Melania teres (Fig 27 way down below) was just “Tennessee Dr. Troost,” too vague to send us on a hunt today, although Goodrich [7] suggested “Small streams of Walden Ridge, Tennessee, flowing eastward.”  Figure 356 is scanned from Burch [10], presumably collected from one of those Walden Ridge teres populations illustrating Goodrich’s concept of the taxon.

For strigosa Lea did a bit better, “Tennessee Dr. Troost, Holston River Dr. Warder.”  This is probably John Aston Warder (1812 – 1883), who was born in Philadelphia and lived in Cincinnati, but traveled broadly [11].

The individual shell depicted in figure (E) down below was collected from Little Flat Creek at the Emory Road bridge in August of 2010 (36.1411, -83.7961). I am offering that particular population of pleurocerids bearing shells with spires drawn out, striate above, as topotypic for M. strigosa for four reasons.  First, apparently at least some of Lea’s sample(s) came from the Holston River drainage of Tennessee, somewhere.  And second, that entire drainage is a mess.

In the last 10 – 12 years I have surveyed the pleurocerid fauna of the entire seven-county region drained by the Holston in East Tennessee, and have only discovered populations of pleurocerids bearing striate shells with spires-drawn-out in two streams: Mossy Creek in Jefferson County, about which you just read in my essay of 6Dec19 (Don’t tell me that you didn’t) and Little Flat Creek in Knox County.  Since Mossy Creek is already the type locality of M. troostiana, it seems an unlikely nominee for the type locality of M. strigosa.  That leaves Flat Creek as the sole remaining candidate.

A=Gap up, B=Gap down, C=arachnoidea, D=spinella, E=strigosa, F=striatula, T=troostiana

The third reason I am offering Flat Creek as the type locality for M. strigosa is that it is in Knox County, and Goodrich [7] subsequently suggested the range of Goniobasis strigosa as “Small streams near Knoxville, Knox County, Tennessee.”  I’m not sure that amounts to a subsequent restriction of type locality, but I do very much value Goodrich’s opinions on matters of this sort.  And the fourth reason I am offering Flat Creek as the type locality for M. strigosa is simply that the shells of the population of pleurocerids living in that little brook match Lea’s figure.  They are not as strongly striate as the Mossy Creek sample that must have been in Isaac Lea’s collection since 1836.  They are merely “striate above.”  OK, good enough.

So what strikes me most about all these pleurocerid populations – much more than the shell striae – is the character that Lea called “spire drawn out” and that Anthony called “spire slender and much elevated.”  In more modern literature, this character is sometimes measured as shell length-to-width ratio, or the ratio of body whorl length to total shell length, although the statistical analysis of ratios is problematic.  In my own research I have preferred the regression of shell width on length [12], or the regression of apex height on body whorl height [13].  Regardless of what that variable is called, or how it is measured, the heritable component can be significant [14].

I am also stricken by the ecological similarities of all these populations.  All of these nominal species – arachnoidea, spinella, strigosa, and the Gap Creek populations that Lea described as porrecta/vittatella – reach maximum abundances in small, rich creeks.  They essentially disappear from the larger rivers of East Tennessee, not unlike Pleurocera simplex, at least in this part of the world.

In exactly that same environment south of Knoxville Goodrich [7] identified populations of pleurocerids bearing striate shells with small body whorls as Goniobasis striatula (Lea 1841/43).  Lea [15] gave the habitat as just “Tennessee,” no help.  Most interestingly, however, Goodrich [16] also identified pleurocerid populations collected from Coahulla Creek in Whitfield County, Georgia, as G. striatula, shown in figure (F) at far right below.  This is one of the very few elements of the pleurocerid fauna that Goodrich admitted might be shared between Tennessee River drainages to the north and drainages of the Alabama/Coosa river system draining south toward the Gulf.

Lea teres [9], Burch teres [10], Lea strigosa [9], Flat Ck (E), Coahulla Ck (F)

We have met the Coahulla Creek pleurocerid fauna before.  It was from Coahulla Creek in the NW corner of Georgia (34.9731, -84.9505) that I collected the sample of P. carinifera I analyzed in Dillon 2011, together with its control population of P. simplex [17].  The rivers and streams at the top of the Alabama/Coosa drainage are separated from drainages of the Tennessee by a couple kilometers at most.  And the genetic differences I found between Coahulla carinifera and simplex were not dramatically different from clavaeformis and simplex populations I sampled all the way through East Tennessee up into SW Virginia.

I did not gather any genetic data on P. striatula when I was sampling pleurocerids for my 2011 study.  But their similarities with Tennessee populations of arachnoidea, spinella, and strigosa in both ecology and shell morphology are striking, are they not?

All of the names given to all of the populations we have reviewed this month: porrecta (Lea 1863), vittatella (Lea 1863), arachnoidea (Anthony 1854), spinella (Lea 1862),  teres (Lea 1841), strigosa (Lea 1841), and striatula (Lea 1841) were proposed more recently than troostiana (Lea 1838).  And all are the same thing.  Populations of one single, highly variable species of pleurocerid snail, best identified as Pleurocera troostiana, extend down the length of the Tennessee River drainage, from SW Virginia through East Tennessee, and even hop the low hills to the upper Coosa drainage in NW Georgia.

Well, we’re not anywhere near done with the subject yet, but I sense that I’m about to lose my audience, all two of you, so let’s bookmark it here.

But our story will continue onward in future episodes, as does the river, downstream into North Alabama.  By the mid-nineteenth century, the fame of Isaac Lea seems to have spread throughout our entire, muscular young country.  And prominent citizens from Huntsville, Tuscumbia, and Florence, Alabama, were scooping up samples of the local gastropod fauna, drying them on their back porches, and packing them for Philadelphia, no different from the citizens of Knoxville and Nashville.

In our next installment... Huntsville hunt!

Notes:

[1] CPP Diary: Yankees at the Gap [4Aug19]

[2] Cryptic phenotypic plasticity in Pleurocera simplex:

• CPP Diary: The spurious Lithasia of Caney Fork [4Sept19]
• CPP Diary: What is Pleurocera ebenum? [3Oct19]

[3] Dillon, R. T. & J. D. Robinson (2007a) The Goniobasis ("Elimia") of southwest Virginia, I.  Population genetic survey.  Report to the Virginia Division of Game and Inland Fisheries.  25 pp.  [PDF]

[4] 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.

[5] Anthony, J.G. (1854) Descriptions of new fluviatile shells of the genus Melania Lam., from the western states of North America.  Annals of the Lyceum of Natural History of New York 6: 80 -132.

[6] This was the infamous “snail darter” dam, that led (perhaps more than any other public works project) to the crystallization of public antipathy for the impoundment of the free-flowing waters of the USA.  For more, see:

Wheeler, W.B. & M.J. McDonald (1986)  TVA and the Tellico Dam 1936 – 1979.  University of Tennessee Press, Knoxville.

[7] Goodrich, C. (1940) The Pleuroceridae of the Ohio River drainage system.  Occas. Pprs. Mus. Zool. Univ. Mich., 417: 1-21.

[8] Lea, Isaac (1862) Description of a new genus (Goniobasis) of the Family Melanidae and eighty-two new species. Proc. Acad. Nat. Sci., Phila., xiv, pp. 262-272.

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

[9] Lea, Isaac (1841) Proceedings o the American Philosophical Society 2: 11 – 15.

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

[10] 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).

[11] Wilson, JG & Fiske, J (1889) Appleton’s Cyclopaedia of American Biography Volume VI. Appleton, NY.

[12] 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]

[13] Dillon, R. T. & J. D. Robinson (2016) The identity of the "fat simplex" population inhabiting Pistol Creek in Maryville, Tennessee.  Ellipsaria 18(2): 16-18. [PDF]

Dillon, R. T. (2016)  Match of Pleurocera gabbiana (Lea, 1862) to populations cryptic under P. simplex (Say, 1825).  Ellipsaria 18(3): 10 - 12.  [PDF]  For more, see:

• The Fat simplex of Maryville matches type [14Oct16]
• One Goodrich Missed: The skinny simplex of Maryville is Pleurocera gabbiana [14Nov16]

[14] Dillon, R. T. & S. J. Jacquemin (2015)  The heritability of shell morphometrics in the freshwater pulmonate gastropod Physa.  PLoS ONE 10(4) e0121962. [html] [PDF]  For more, see:

• The heritability of shell morphology in Physa h^2 = O.819! [15Apr15]

[15] This name is another cold mess.  Lea originally described it as “Melania striata” in that same pair of 1841/43 publications cited at [9] above.  He then discovered that the specific nomen striata was preoccupied, amending it to striatula elsewhere in 1843 (Proceedings of the American Philosophical Society 2:237).  Goodness gracious it will be nice to be done with stuff like this.

[16] Goodrich, C. (1941) Pleuroceridae of the small streams of the Alabama River system. Occas. Pprs. Mus. Zool. Univ. Mich., 427, 1-10.

[17] Dillon, R. T. (2011)  Robust shell phenotype is a local response to stream size in the genus Pleurocera (Rafinesque 1818). Malacologia 53: 265-277 [PDF]. For more, see:

• Mobile Basin III: Pleurocera puzzles [12Oct09]
• Goodbye Goniobasis, Farewell Elimia [23Mar11]
  

On the Trail of Professor Troost

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023b)  On the Trail of Professor Troost.  Pp 35 – 40 in The Freshwater Gastropods of North America Volume 6, Yankees at The Gap, and Other Essays.  FWGNA Project, Charleston, SC.

The Dutch-American geologist Gerard Troost [1] had already led a full life when he stepped off the boat in Philadelphia in 1810.  He had earned a doctorate in medicine from the University of Leyden and done graduate work in crystallography at Paris.  He had been wounded in the Napoleonic Wars, served as chief scientist on an expedition to Java, and was captured and ransomed by privateers, twice, both French and English.  Sometimes we imagine that our lives today are interesting.

Gerard Troost (1776-1850)

In 1812 Troost was elected the first president of the Academy of Natural Sciences, a post he held for five years, tutoring Isaac Lea and Lardner Vanuxem.  Then in 1825 he sailed down The Ohio to “happiness, enlightenment and prosperity” at New Harmony, Indiana, with Thomas Say at his side.  Gerard Troost was not a malacologist, but he certainly had the names of a couple good ones in his Rolodex.

Troost was called away from New Harmony after just two years singing in the choir utopian by the offer of a professorship at the University of Nashville, from whence he was appointed the Tennessee State Geologist in 1831.  These duties sent him on lengthy explorations throughout the Volunteer State, bringing him to the verge of many rivers and streams blessed with rich faunas of freshwater mollusks.  He was often accompanied in the field by Dr. Richard Owen Currey (1816 – 1865), whom we mentioned in October [2], who assumed Troost’s duties as Professor of Geology in Nashville when Troost died in 1850.

Troost apparently began sending shells to his good friend Isaac Lea in Philadelphia very shortly after his 1831 appointment and continued for quite a few years.  Leafing through the Lea bibliography in Scudder [3] I see that at least 25 – 30 new species of unionids Lea described in the 1830s and 1840s were “sent to me by Professor Troost.”  And it was in honor of Professor Troost that Lea described Melania troostiana around 1838ish, approximately.

It will be remembered from last month’s post that through most of his career Isaac Lea was locked in a torrid race for the naming of species, and that the precise dates of his publications, calculated down to the afternoon, mattered a great deal, at least to him.  To establish what any of those dates might actually have been, however, demands scholarship of a higher caliber than the popgun your humble essayist comes packing.

Lea read his initial description of Melania troostiana in brief, Latinate form before the American Philosophical Society on November 4, 1836.  His (more complete, English) description appeared in the Transactions Volume 6 (New Series), Article 1, which (according to Scudder) was “printed and ready for publication” June 15, 1838 [4].  If you download a copy of Transactions Volume 6 from the Biodiversity Heritage Library, however, it very clearly states 1839 on the title page.  And (apparently in error) both Tryon [5] and Goodrich [6] give Lea’s date for the publication of troostiana as 1841.  Burch [7] and Graf [8] harken back to 1838.

But here is the thing that matters to us today.  Melania troostiana was early.  Regardless of its actual publication date, Lea’s description of Gerard Troost’s eponymous pleurocerid certainly preceded the torrent of gastropod nomina that spilled from his pen beginning in 1841 with his “New Fresh Water and Land Shells” series.  If you run your finger down the list of 199 canonical pleurocerid nomina forwarded to us by Goodrich/Burch, troostiana falls out #39 [9]. It was the second species of pleurocerid snail that Lea ever described, that stuck [10].

Lea gave the habitat of M. troostiana as “Mossy Creek, Jefferson County, Ten,” which is quite atypically precise, by 19^th century standards.  His description led with “shell elevated” and followed with “thickly striated.”  But in his remarks, he focused primarily on the “sharp carina” demonstrated by the shell, and secondarily on the “numerous striae,” which reminded him of what we call today Pleurocera virginica. 

If you’re not entirely sure about the distinction between a carination and a striation, click the image below for a primer on shell morphology.

I speculate that the nomen “Melania troostiana” receded into obscurity in the 20^th century for two reasons.  First, Lea’s 1838 figure doesn’t match any pleurocerid that currently lives or ever has lived in the state of Tennessee especially well, particularly with respect to that dramatic carination that extends from the juvenile into the adult whorls.  Hence all subsequent authors have restricted its range to Mossy Creek.

Pleurocera troostiana (Click for shell terminology)

And second, Mossy Creek is a scummy mess.  I first had the occasion to visit that unfortunate little body of water in the summer of 2011, when I was surveying the Tennessee drainage above Chattanooga for the FWGTN web resource.  The Mossy Creek catchment is a mixture of overly-grazed pastureland and dusty rock quarries, draining directly through Jefferson City into Cherokee Reservoir.  The creek has obviously suffered decades of erosion, sedimentation, and enrichment.  And at none of the (rather few) points of access did I find any pleurocerids whatsoever.

My resolve was reinforced, however, by the troostiana figure in Burch [7], which looked both modern and plausible.  The UMMZ does hold three lots identified as P. troostiana collected from Mossy Creek by somebody named “Andrews.”  I don’t see any collection dates in their online database, but it seems possible to me that Andrews might have been a Goodrich contemporary, and hence his samples might be relatively recent.  And most interestingly, Burch’s figure, almost certainly from one of those UMMZ lots, does not show that weirdly strong carination.

So I returned to Mossy Creek this past spring, and by dint of persistence was able to find exactly N = 6 topotypic specimens of P. troostiana at the Old Andrew Johnson Highway bridge (36.1272, -83.4862).  The shells borne by all six of those specimens were striate, although in one case (T1, above) the striae became obsolete in spots.  Three of the shells matched the figure in Burch quite closely.  And shells of two individuals (T2, above) were so strongly striate that a carination developed reminiscent of Lea’s original figure. figure.

Seven paragraphs ago I wrote that “the” thing that matters to us today is that the nomen, “Melania troostiana” was early.  Let me modify that slightly.  The earliness of the taxonomic act is certainly important.  But just as important is the tremendous variability in shell striation depicted in the figure above.  All four of those shells were borne by a single population of snails inhabiting a single little ten km creek in East Tennessee.  Let that sink in a minute.

Goodrich devoted the entirety of paper number V in his “Studies of the Gastropod Family Pleuroceridae” series [12] to documenting the “transient, sporadic” character of shell “spirals,” or striations.  Selecting “Goniobasis porrecta Lea of the big hillside spring at Cumberland Gap” as one of his many examples, Goodrich observed: 

“No multistriate specimens have been seen as from the type locality, but such individuals amount to 32.4 per cent of seventy-seven shells taken from Gap Spring Creek about four miles below the spring.”

Hey kids, test your memory!  We devoted our entire essay back in August to cryptic phenotypic plasticity in the pleurocerid populations of Gap Spring Creek.  With what name did I identify those populations that Isaac Lea described in 1863 as Goniobasis porrecta?  Answer at footnote [13] below!  Next month, we’ll find out why.

Notes:

[1] The biographical details for this month’s essay, as well as the striking figure, were extracted from a “Sketch of Gerard Troost,” published anonymously in the June, 1894 issue of The Popular Science Monthly, pp 258 – 264.

[2] It was Currey who sent Isaac Lea the sample of pleurocerids from “Robinson County, Tenn” he described as Melania ebenum in 1843.  See:

• CPP Diary: What is Pleurocera (aka Melania, aka Goniobasis, aka Elimia) ebenum?  [3Oct19]

[3] Scudder, N. P. (1885)  Bibliographies of American naturalists – II. The published writings of Isaac Lea, LL.D.  Bull. US National Museum 23: 1 – 278.

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

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

[6] Goodrich, C. (1940) The Pleuroceridae of the Ohio River drainage system.  Occas. Pprs. Mus. Zool. Univ. Mich., 417: 1-21.

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

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

[9] The first valid species of pleurocerid snail described by Isaac Lea, by the Goodrich/Burch canon, was Melania acuta (Lea 1830).  This is not the Pleurocera acuta of Say (1821).  This is a “longitudinally undulated and transversely lineated” North Alabama species attributed to Goniobasis by Goodrich, or Elimia by Burch.  It may be a synonym of laqueata (Say 1829).  Or it is possible that Lea's (1830) acuta is a senior synonym of what we are calling troostiana (Lea 1838), in which case we'd have to salt it and butter it as a double-predestinarian hominy under acuta (Say 1821).  Crap, I hate this sort of stuff, and am clean out of patience with it.

[10] Nineteen of the 38 canonical pleurocerid taxa older than 1838 were described by Lea’s nemesis, Timothy Abbott Conrad, which must have ticked him off royally.  Another 12 were from Thomas Say, whom Lea didn’t much care for either, apparently.  See last month's post:

• Isaac Lea drives me nuts [5Nov19]

[11] I’ll post a dot-map showing the site of my Mossy Creek collection next month.

[12] Goodrich, C. (1935)  Studies of the gastropod family Pleuroceridae – V.  Occasional Papers of the Museum of Zoology, University of Michigan 318: 1 – 12.

[13] I identified the Gap Creek population of G. porrecta as Pleurocera troostiana, of course!  That’s where I’ve been going with this entire essay.  Shame on you for reading this footnote.  Go back and read:

• CPP Diary: Yankees at The Gap [4Aug19]