The birth, death, and resurrection of Melania acutocarinata

It was from the pen of our old buddy Isaac Lea [5Nov19], early on a frosty morning in 1841, that Melania acuto-carinata was born, in brief Latinate form, number 46 in a litter of 57 pleurocerid puppies [1].  Among its more famous siblings were #2 castanea [12Nov24], #7 ebenum [3Oct19], #10 clavaeformis [20Feb07, 12Oct09], #25 virgata [9May23], and #37 edgariana [5June20].  Lea followed with more complete English descriptions and figures of the entire litter in 1843 [2].

The type locality of Melania acuto-carinata was vague, “Tenn., Dr Currey.”  We first met Dr. Richard Owen Currey (1816 – 1865), impeccably credentialed with Presbyterian heritage and doctorate from the University of Pennsylvania, back in [3Oct19].  Currey was born and raised in Nashville but moved to Knoxville in 1846 to become “the first person with an earned doctorate to teach science” at East Tennessee University, later the University of Tennessee [3].

Melania acuto-carinata [2]

Lea’s description of the acuto-carinata shell was almost as vague as its type locality: “It seems to be distinct in its large carina which extends over all the whorls, but it is scarcely distinct on the last.”  Nevertheless, the nomen was launched into malacological stardom in 1858 by the English naturalists Henry and Arthur Adams, in their justifiably maligned “Genera of Recent Mollusca” [4].

It seems highly unlikely to me that either of the Adams brothers ever laid eyes on a North American pleurocerid snail in their entire, justifiably-maligned lives.  Tryon [5] reprinted their classification verbatim in 1873, “in order that the insufficiency of their genera may become more apparent from the incongruous assemblage of shells of which they have composed them.” 

 

Among the 16 genera Henry and Arthur recognized in the Melanidae was Io (of Lea) “remarkable for the peculiar elongation of the axis anteriorly, and for the spinose nature of the last whorl.”  Fine.  Then, as a subgenus of Io (good grief!) the Adams brothers proposed, “Elimia” for pleurocerids bearing shells fusiformly ovate, “whorls reticulate or nodulose, carinate in the middle.”  And under Elimia they listed 16 apparently random pleurocerid specific nomina in alphabetical order, the first of which was “acuticarinata, Lea,” without the dash, misspelled, bearing a shell that is neither reticulate nor nodulose.

 

Tryon dismissed the Adams classification from further consideration and assigned acutocarinata to the genus Goniobasis, newly proposed by his mentor Isaac Lea in 1862 [6].  And pretty much the entire malacological community fell in line with Tryon and Lea, most notably Calvin Goodrich [23Jan07], toward whom our attention now turns.

 

In a 1939 paper that should be better known than it is, Goodrich [7] used Goniobasis acutocarinata as an example of “depauperization,” by which he meant “the outward manifestation of disease, accident or malnutrition or a reaction to inimical environment.”  He wrote: 

“In Goniobasis, very loose coiling appears to be a sign of depauperization.  Goniobasis acutocarinata, although described as a species, has not been found in pure colonies. Lea, its author, had only one specimen.  The shell occurs as a rare variant among G. clavaeformis in springs and spring branches of East Tennessee.” 

For that reason, in his influential review of 1940, Goodrich [8] synonymized Melania acutocarinata Lea 1841 under Goniobasis clavaeformis (Lea 1841).  And that should have been the end of it.  Pleurocerid nomina that did not survive Calvin Goodrich’s 1930 – 1950 piecemeal crusade to monograph the family were not, as a rule, listed or figured in the Burch Bible [9].  They have died, been buried, and forgotten, RIP.

 

P. clavaeformis from Burch [9]

And that is indeed what happened to 12 of the 13 specific nomina [10] synonymized under clavaeformis by Goodrich in 1940.  They disappeared, never to be seen again.  But not acutocarinata.

Although generally following Goodrich quite closely, in the 1980s Jack Burch [9] gave Goodrich’s system one great big kick and a bunch of little tiny anonymous tweaks [11].  Out of a sense obligation to the letter of the ICZN law [12], Burch elected to resurrect the Adams brothers’ obscure Elimia in place of the widely used Goniobasis, confounding the work of Lea, Tryon, Goodrich and everybody else over the previous hundred years.  Following Henry Pilsbry [26Jan21] and Pilsbry’s local collaborator Samuel Rhoads [13, 14], Burch selected acutocarinata as the type of the Adams polyglot genus, by virtue of its first place in the alphabetized list of 16 odd lot species included.

 

And among his tweaks, Burch saved Isaac Lea’s acutocarinata.  To be precise, what he did was exhume two acutocarinata specimens from the UMMZ collection (Figs 404 and 405 above) and figure them alongside a singleton specimen of typical clavaeformis (Fig 403), labeling both of the former “E. acutocarinata = ? E. clavaeformis.”  Why did Burch dump 12 of Goodrich’s clavaeformis synonyms and double-figure the thirteenth?  I don’t know.  If it was a coincidence that acutocarinata was the type of his resurrected Elimia, it was certainly a convenient one.  But for whatever reason, Isaac Lea’s 1841 acutocarinata was spared into a kind of taxonomic purgatory, a place of shadows, neither alive nor dead.

 

In retrospect, I myself should have rescued the nomen from the netherworld for use at the subspecies level in my 2011 paper on Goodrichian Taxon Shift [15], later renamed cryptic phenotypic plasticity (CPP) [16].  Longtime readers will remember that I selected three sites in East Tennessee (and one in North Georgia) inhabited upstream by what I was calling, at that time, Goniobasis acutocarinata, in the mid-reaches by what I was calling, at that time, Goniobasis clavaeformis, and downstream by what I was calling, at that time, Pleurocera unciale.  Those sites included the famous [17] Indian Creek tributary of the Powell on the VA/TN border (IC, map way down below) and the even more famous [19] Pistol Creek of Maryville (PC), as well as the (rather obscure) Lick Creek tributary (LC) of the Hiwassee.

 

My allozyme analysis showed that each acutocarinata population was more genetically similar to its downstream clavaeformis population than to any other acutocarinata, and that each unciale population was genetically more similar to its upstream clavaeformis population than to any other unciale.  On that basis I folded both acutocarinata (no surprise) and unciale (big surprise) under clavaeformis, and both Goniobasis and Elimia under Pleurocera.

 

P. clavaeformis in Indian Creek, Va - Tn

I elected, however, to save uncialis/unciale at the subspecific level, as Pleurocera clavaeformis unciale (Hald 1841), both because of its utility to describe a familiar shell form, and its indexing function to the older scientific literature.  Note that subspecific designation does not carry with it any assumption regarding the heritability of the distinguishing characteristics, much less genetic relationships [20].  It’s just useful.

By the same reasoning, I should also have elevated acutocarinata back up from taxonomic purgatory to the subspecific level, as Pleurocera clavaeformis acutocarinata (Lea 1841).  That should have happened back in 2011.  In my own defense, all I can offer is that unciale was recognized at the species level by Goodrich in 1940, and acutocarinata was not, and resurrecting old pleurocerid names from the nether regions is not the direction anybody wants to go.  But I’ve done it subsequently [21].  The indexing utility of Lea’s nomen acutocarinata is just as significant as that of Haldeman’s unciale/uncialis, probably greater, and the shell morphology just as distinctive.

 

Then let it be so, better late than never.  This month I have added a new Pleurocera clavaeformis acutocarinata page to the FWGNA website, and a new photo to the FWGTN gallery, and a new entry in the FWGTN dichotomous key – the second time I have found myself doing this in recent memory [22].  The number of freshwater gastropod species now covered by the FWGNA web resource is 145 + 1 = 146. 

 

And I have dug back through my old collections and re-identified 22 populations of P. clavaeformis from the typical subspecies to acutocarinata.  Almost all of these inhabit small streams south of Knoxville, primarily direct tributaries of the main river or of the Hiwassee.  The Indian Creek population, way up on the Virginia/Tennessee Line, appears to be an outlier.

 

In all my earlier writings on Goodrichian Taxon Shift and CPP, I have tended to favor explanations that are not heritably genetic.  Although I have always left room for natural selection, most of the column inches in the discussion sections of the papers I have published on this subject [23] focus on the (many and striking) laboratory demonstrations of ecophenotypic plasticity in freshwater gastropod shell morphology.

 

Reidentified acutocarinata in blue

Quite recently a third possible explanation has dawned on me, in the specific case of the apparent transition between P. clavaeformis populations bearing shells of the typical morphology, and those bearing shells of the acutocarinata morphology.  Hybridization [24].

Populations of P. clavaeformis reach maximum abundance in streams of moderate size – marginally wadeable, where you’d bait up for redeye bass and bream.  Populations certainly extend upstream into colder waters suitable for trout, however, where in East Tennessee they bump into big populations of P. troostiana [25].

 

It is conceivable to me that Pleurocera clavaeformis acutocarinata may be a clavaeformis x troostiana hybrid.  I don’t have any genetic evidence of that [26].  This is just a speculation, based on the acutocarinata shell, which appears morphologically intermediate between the two species, both in its carination and in its overall length-to-width, body-whorl-to-apex slenderness.

 

But to conclude, I must emphasize.  Whether the shell morphological distinction between the (now three) subspecies of P. clavaeformis results from adaptation, hybridization, or ecophenotypic plasticity is irrelevant to their subspecific identity.  Here we resurrect Lea’s 1841 nomen acutocarinata because it is a useful descriptor of shell form, and because it has appeared frequently in the published literature.  And will appear again.  Stay tuned.

Notes:

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

 

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

 

[3] Quoting the Richard Owen Currey entry in the University of Tennessee “Volopedia” archives: “In 1861, Currey entered Confederate service as a chaplain-surgeon. In 1865, he started caring for Union prisoners in North Carolina. He died while working in a disease-infested hospital on February 17, 1865.” He must have been a wonderful man.  It would have been an honor to shake his hand.

 

[4] Adams, Henry and Arthur (1854 - 1858) The Genera of Recent Mollusca Arranged According to Their Organization. In Three Volumes.  London: J. Van Voorst.  The Melanidae is covered in Volume 1, pp 293 – 311.

 

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

 

[6] Lea, Isaac (1862) Description of a new genus (Goniobasis) of the Family Melanidae and eighty-two new species. Proceedings of the Academy of Natural Science of Philadelphia 19: 262 – 272.

 

[7] Goodrich, Calvin (1939) Aspects of depauperization.  The Nautilus 52: 124 – 128.

 

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

 

[9] 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).

 

[10] Which I will not list, not even in the footnote of an obscure blog post.

 

[11] For the record, here is the complete text of Burch’s Supplemental Note #23: “Elimia H. and A. Adams (type species Melania acutocarinata Lea 1841 = Melania clavaeformis Lea 1841) is used in place of its better-known synonym Goniobasis Lea 1862 (type species Goniobasis osculata Lea 1862).  The classification of the genus Elimia presented here, and the distribution of the various recognized species and subspecies, is that of Goodrich (1930a, 1936, 1939d, e, 1940d, 1941a, b, c, 1942b, 1944d, 1945, 1950).  No attempt has been made to assess the taxonomic validity of the species and subspecies.”

 

[12] Burch, J. B. 2001. On the genus name Goniobasis (Elimia - Gastropoda: Pleuroceridae) and other recent nomenclatural inconsistencies. Walkerana 12:97-105.

 

[13] Pilsbry, H. and S. Rhoads. 1896. Contributions to the Zoology of Tennessee, Number 4, Mollusca. Proc. Acad. Nat. Sci. Phila. 1896:487-506.

 

[14] Note, however, that Pilsbry never used “Elimia” himself.  His imperial majesty continued to prefer Goniobasis in every paper he ever wrote or edited for The Nautilus.  And all the labels in the ANSP collection read “Goniobasis” to this day.  For example:

• Pilsbry, H. 1916. Goniobasis in western Pennsylvania. Nautilus 30:4-5.

[15] 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]

 

[16] For an entry into the rather extensive literature of CPP in North American pleurocerid snails, see:

• Goodrichian taxon shift [20Feb07]
• Mobile Basin III: Pleurocera puzzles [12Oct09]
• Pleurocera acuta is Pleurocera canaliculata [3June13]
• Pleurocera canaliculata and the process of scientific discovery [18June13]
• Elimia livescens and Lithasia obovata are Pleurocera semicarinata [11July14]

[17] I was wading in waters of Indian Creek, just like John, when the scales fell from my eyes.  John Robinson and I published a gray-literature report on those findings to the VDGIF in 2007 [18], and I coined the term “Goodrichian Taxon Shift” on this blog.  See:

• Goodrichian Taxon Shift [20Feb07]

[18] Dillon, R. T. & J. D. Robinson (2007b) The Goniobasis ("Elimia") of southwest Virginia, II. Shell morphological variation in Goniobasis clavaeformis. Report to the Virginia Division of Game and Inland Fisheries, contract 2006-9308. 12 pp. [pdf]

 

[19] It was at Pistol Creek that I ultimately discovered a forgotten pleurocerid species cryptic under P. simplex.  See:

• The cryptic Pleurocera of Maryville [13Sept16]
• The fat simplex of Maryville matches type [14Oct16]
• One Goodrich missed: The skinny simplex of Maryville is Pleurocera gabbiana [14Nov16]

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

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

[21] I resurrected Isaac Lea’s (1862) lyonii, previously subsumed by Goodrich (1940) under laqueata, as a subspecies of P. troostiana in:

• The return of Captain Lyon [6July20]

[22]  I added a new Pleurocera laqueata castanea page to the FWGNA website last fall, with corresponding entries in the FWGTN species gallery and dichotomous key.  See:

• Reticulate evolution in the North American Pleuroceridae [12Nov24]

[23] Published papers on CPP:

• 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]
• Dillon, R. T., S. J. Jacquemin & M. Pyron (2013) Cryptic phenotypic plasticity in populations of the freshwater prosobranch snail, Pleurocera canaliculata.  Hydrobiologia 709: 117-127.  [pdf]
• Dillon, R. T. (2014) Cryptic phenotypic plasticity in populations of the North American freshwater gastropod, Pleurocera semicarinata.  Zoological Studies 53:31. [pdf]

[24] For more on hybridization in pleurocerids, see:

• Widespread hybridization between Pleurocera laqueata and P. troostiana in streams of the Tennessee/Cumberland [15Oct24]
• Reticulate evolution in the North American Pleuroceridae [12Nov24]

[25] And simplex. And gabbiana.  But I don’t think that is relevant to my argument here.

 

[26] Just the opposite, actually.  In our VDGIF allozyme study [27], John Robinson and I did run gels on N = 31 G. clavaeformis (C1) and N = 30 G. “arachnoidea” (A1 = troostiana) from Indian Creek, finding a little bit of evidence of mixing at some loci, but fixed differences at three others.

 

[27] 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, contract 2006-9308. 25 pp. [pdf]