Dr. Rob Dillon, Coordinator

Thursday, December 21, 2017

Pet Shop Malacology

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023c)  Pet Shop Malacology.  Pp 37 – 44 in The Freshwater Gastropods of North America Volume 7, Collected in Turn One, and Other EssaysFWGNA Project, Charleston, SC.

Back in the early 1960s, the very first aquarium shop to open its doors in Waynesboro, Virginia, was an aquatic wonderland called “Fin Fair.”  Sometimes, especially in the winter, I prevailed over my father to drive me to their store on West Main Street just so I could stroll among the dozens of tanks filled with glistening little jewels of nature.  Of course, I wanted my own aquarium.  I kept a series of aquaria through my childhood, as I grew up, and the things in them didn’t.

from Brookana Ashley Patton
And of course, any proper aquarium must have snails to scavenge the uneaten food, am I right?  In the 1960s and 1970s, in my personal experience, almost all I ever saw for sale were “ramshorns,” apparently Helisoma trivolvis.  No fancy colors, either.  Just plain, brown, “ramshorns.”

So you may be able to imagine, knowing me as you all do, the impression made by the first “mystery snail” I ever saw [1].  They were Pomacea paludosa, almost certainly wild-collected down in Florida, and they were huge!  The pet shop owner explained to me that they laid eggs out of water, the mystery being that nobody ever saw them do it.  I bought three mystery snails with my hard-earned allowance money, and I don’t think they lasted two weeks [2].

But a couple years later, the Dillons went on a family vacation down to Florida, and among our many adventures, booked passage on a glass bottom boat out of Silver Springs.  I remember the experience being very much like sailing across the top of Fin Fair.  And almost immediately, my eyes were attracted down through the schools of catfish and bream to the bottom of the springs where, to my fascination, lay small piles of mystery snail shells.  My father boosted me over the back fence on the way out to the parking lot, and I was able to snatch a couple empty shells from the marshy margins of the springs.  Watch for gators, he said.  Great father.

It is difficult for me to place myself at age 12 here in Charleston, 2017.  But one thing is certain.  The Charleston area today is blanketed by big-box pet stores - PetSmart (5 outlets) and PetCo (4 outlets).  And the eyes of any kid walking into the well-stocked aquarium departments of any of these giant retail outlets will fall on two types of freshwater gastropods, both spectacular in their own way: modern-day mystery snails [1] and nerites.

The mystery snail of the modern aquarium hobby is Pomacea diffusa, ne bridgesii [3].  They are big enough and active enough to have a personality, and charmingly diverse in coloration, as witnessed by the lovely photo montage above.  I surveyed several of the local big-box retailers, and found Black, Ivory, Blue, and Gold varieties, which for some reason PetCo calls “Gold Inca.”

The inheritance of color polymorphism in P. diffusa is a fascinating topic, to which we may return in a future post.  I cannot find anything published about it in the scientific literature, but somebody, somewhere, really seems to know what he is doing. If any member of my vast readership has any good information on the striking color polymorphisms manifest in commercial P. diffusa stocks, especially where these things are ultimately coming from, please contact me at your earliest convenience [4].

Wild Pomacea populations range through the lower latitudes of the New World, specializing on floating macrobenthic vegetation [5].  They are especially large-bodied as freshwater gastropods go, with even larger mouths with specialized lips to manipulate leafy greens, and even larger teeth.  Their shells are bulbous and surprisingly light, adapted to enfold an air bubble, making their bearers positively buoyant.  The reproductive adaptations of Pomacea are weird and wonderful – climbing up out of the water to lay huge clutches of huge eggs, typically on emergent vegetation.

Now here’s a riddle.  Among the prosobranch fauna of warm freshwaters, what is the opposite of Pomacea?  How about an unspecialized grazer of benthic periphyton with an especially heavy shell adapted to high-energy environments in the Old World?  Laying tiny eggs that go down?  How about the nerites?

Zebra nerite "N. natalensis" from Wikipedia
Nerites are the best known group of freshwater gastropods about which nothing is known [6, 12].  Although much smaller than the mystery snails, the nerites marketed to the aquarium hobby are even more eye-catchingly colorful.  All the big-box stores sell a nice variety.  Our hypothetical twelve-year-old-boy would find “tiger nerites” and “zebra nerites” in the local PetCo, and “black nerites” and “mixed nerites” at the PetSmart.

Both the tigers and the zebras are labelled as “Nerita natalensis” in my local PetCo, but I am just not sure.  I can google around the internet like the best college freshman, and I did (in fact) find a variety of Wikipedia and hobbyist-type references to Neritina (or Nerita) natalensis, depicting the tiger-striped snail sold by PetCo, listing the native habitat as the freshwater-tidal and brackish mangrove-type habitats of East Africa.  The problem is that I pulled my trusty copy of D. S. Brown [7] off the shelf, and the PetCo nerites don’t really match Brown’s figures of Neritina natalensis.  They do match the figures labelled “Vittina coromandeliana” and “Vittina turrita” in the paper by Ting Hui Ng we reviewed back in October [8], both of which are elements of the Oriental / Pacific Islands fauna, not Africa.

Oh, good!  Ng and colleagues got CO1 sequences for their Singapore samples of Neritina (Vittina).  That should help us out here, right?  Nope, sequence data are worse than useless in this situation [9].  The individual Vittina turrita sequenced by Ng didn’t match anything in GenBank.  The V. coromandeliana sequence did match a GenBank sequence labelled as turrita, as did the sequence of a third nerite from the Singapore pet shops, which Ng identified as V. waigiensis.  Quoting Ng directly: 
“Two individuals identified by morphology as Vittina coromandeliana and Vittina waigiensis were 99–100% matched to two separate submissions on GenBank that were identified as Vittina turrita. Neither study included photographs of the species, nor could the sequenced individuals be located; because the two GenBank sequences for Vittina turrita were separated by a 4.5% uncorrected pairwise distance, we retained our morphology-based identifications.” 
So that brings up Neritina (Vittina) waigiensis, which may be what is lying sullen at the bottom of the tank labelled “mixed nerites” in my local PetSmart.  That’s the impression I got from my google search, anyway.  Almost all neritid populations demonstrate striking shell color polymorphism, but the snails that pet stores tend to call the “red nerite” and the internet usually identifies as Neritina waigiensis beat anything I have ever seen.  The combinations mix a delicious-looking strawberry-red color with brilliant gold and black zig-zags.  In fact, it seems possible to me that the nerites separated out as zebras and tigers in the big-box pet stores are almost within the range of color polymorphism of waigiensis.  I don’t know.
Neritna (Vittina) waigiensis
Van Bentham Jutting [10] gave the range of Neritina (Vittina) waigiensis as “especially in the eastern part of the Malay Archipelago, also in the Philippines.”  I can’t discover anything about its habitat or life history.  The species appears in both freshwater and marine references.  Most of the Oriental / Pacific Island neritids live in rapidly-flowing streams that empty directly into the sea, their eggs hatching into planktonic larvae swept down to develop into marine juveniles, migrating back into fresh water [11].  Other tropical neritid species inhabit tidal, mangrove-type environments, laying eggs that hatch into crawling juveniles, like normal freshwater prosobranchs.  The various popular aquarium nerite species seem to manifest both types of life cycles, as may be judged on YouTube, if you’d like to conduct your own cutting-edge research in freshwater neritid biology.

So we’ll close this month’s essay with one more general observation on the oppositeness of the mystery snails and the nerites, and a final point of ironic similarity.  Pomacea diffusa stocks are all (I feel sure) captive-bred.  But the nerites must be gathered from the wild – I cannot imagine an aquarist completing the life cycle of a neritid in culture.

From Chris Lukhaup
What this means is that whoever is gathering these strikingly colorful tropical nerites, whatever they are, does not want us to know where he is finding them – this is their “trade secret,” in a sense.  In fact, it will actually be to the perceived advantage of the sellers to mislead the buyers about all aspects of their malacological commodity – especially range and habitat, probably even identity.  I wouldn’t be surprised if, at some point in the supply chain between the hunter/gatherer source and your neighborhood Big-box aquarium supply outlet, the East African name “Nerita natalensis” is written in grease pencil on aquaria full oriental nerites fraudulently, in a deliberate effort to mislead.

And the ironic similarity is this.  For all their tremendous popularity in the worldwide aquarium hobby, the colorful varieties of mystery snails are every bit as genetically mysterious as the colorful varieties of nerites are ecologically mysterious.  Both categories of information seem to be jealously-guarded trade secrets.  Such are the challenges of Pet shop malacology, 2017.


[1] Common names make no sense, and there’s no sense in trying to make sense out of them.  Sometime between the 1970s and the 2000s, the name “mystery snail” was transferred to viviparids like Bellamya (Cipangopaludina), the mystery being that nobody ever saw them lay eggs.  And the various Pomacea became known as “Apple Snails.”  So that is the convention followed in both the Perera & Walls (1996) “Apple Snails in the Aquarium,” and the Turgeon et al. (1998) “Common and Scientific Names of Mollusks.”   But I think the bad press suffered by the larger, invasive, pest species of Apple snails, variously identified as Pomacea canaliculata/insularum/maculata, prompted the aquarium trade to move back to writing “mystery snail” on tanks of Pomacea bridgesii/diffusa.  Only the pest Pomacea species are still called “apple snails” by the aquarium hobby.

[2] I didn’t know what to feed them.

[3] Rawlings, T.A., K. A. Hayes, R. H. Cowie, and T. M. Collins (2007)  The identity, distribution, and impacts of non-native apple snails in the continental United States.  BMC Evolutionary Biology 7: 97.

[4] I have seen the (2004) paper by our good friend Yoichi Yusa on the inheritance of body color polymorphism in Pomacea canaliculata.  The situation in P. diffusa is obviously more complicated.

[5] Hayes, K. A. et al. (2015)  Insights from an integrated view of the biology of apple snails (Caenogastropoda: Ampullariidae)  Malacologia 58: 245 – 302.

[6] Well, European Theodoxus is fairly well studied.  There’s lots of general biology in Fretter & Graham’s (1962) “British Prosobranch Molluscs.”  And see my book pp 85 – 86 for diet & habitat.

[7] Brown, D. S. (1994) Freshwater Snails of Africa and their Medical Importance.  London: Taylor & Francis.

[8] Ng, Ting Hui, Tan SK, Wong WH, Meier R, Chan S-Y, Tan HH, Yeo DCJ (2016) Molluscs for Sale: Assessment of Freshwater Gastropods and Bivalves in the Ornamental Pet Trade. PLoS ONE 11(8): e0161130.  Review:
  • What’s Out There? [9Oct17]
 [9] Here’s another vivid demonstration of a point we have made repeatedly on this blog.  Sequence data are a dependent variable, not an independent.  They cannot be used to elucidate the systematics or evolution of an unknown study group.  Only if we have a previous hypothesis about the evolution of a group, from good, hard science, can sequence data be interpreted.  See:
[10] van Benthem Jutting WSS. Systematic studies on the non-marine Mollusca of the Indo-Australian archipelago: V. Critical revision of the Javanese freshwater gastropods. Treubia 1956; 23: 259–477.

[11] Alison Haynes published several papers on the neritid fauna of the Pacific Islands in the 1980s, which although not especially helpful to identify the Malaysian/Philippine species of immediate interest in this essay, are useful for the biology of the family.  See:

Haynes, A. (1988)  Notes on the stream neritids (Gastropoda: Prosobranchia) of Oceania.  Micronesica 21: 93 – 102.  I’ve also heard that her (2001) book is good, but don’t have access to a copy.

[12] Several weeks subsequent to the post of this blog, my attention was called to the 2016 publication of an expensive, two-volume set entitled "Neritidae of the World" by Thomas Eichhorst.  I understand the work is excellent, but have not seen a copy.

Monday, November 6, 2017

Loved to Death?

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023c)  Loved to Death?  Pp 29 – 35 in The Freshwater Gastropods of North America Volume 7, Collected in Turn One, and Other EssaysFWGNA Project, Charleston, SC.

Back in 1976, when I first joined the American Malacological Union, the community of shell collectors played an important role in the day-to-day operations of the society.  It seemed to me that the amateurs actually outnumbered the professionals at our annual meetings.  Shell clubs ran the registration table, operated the A/V equipment, and sponsored the receptions.  Receptions, heck – the Houston Shell Club threw a rip-snorting party, with music, and dancing, and pretty girls.  And (then-Treasurer) Connie Boone came through kissing everybody who held still.  Man, those were the days!

My 1974 edition of a 1966 classic
So the climax of the annual meeting of the American Malacological Union in those golden days was always the shell auction, for the benefit of the student fund.  Dick Petit would get half-tuned and wisecrack from lot to lot of colorful specimen shells, offering drop-dead gorgeous little jewels of nature to the highest bidder, and some of the prices paid were eye-popping.

Although I myself never offered any bids for any of the lovely seashells on auction, I felt a strong connection to those who did.  I was quite the hobbyist myself in my youth.  I did collect a lot of marine gastropods and bivalves for their shells, and traded shells with friends all over the world, and (yes) did indeed purchase specimen shells from shell dealers and shell shops, till the day I left home for college.  Shell collecting gave me my start in malacology.

Alas, in 1996 the American Malacological Union threw it all away.  Citing vague conservation concerns, that summer the AMU Council [1] banned the sale or trade of shells at annual meetings, implying strongly as it did that overcollecting by hobbyists posed a threat to natural mollusk populations.  The hobbyists felt as though they had been insulted, which they had, and they left the AMU and never came back.  It was the stupidest thing ever done by a roomful of mollusk people.

So last month we took a peek into the worldwide trade in living freshwater gastropods for the aquarium hobby [2].  Most of the 47 species at least occasionally available from Singapore, the primary wholesale exporter of aquarium stock to the global marketplace, are widespread and trashy, as one might expect.  But our colleague Ting Hui Ng and her coauthors [3] also identified several freshwater gastropod species as “narrowly endemic,” mostly Tylomelania and other Southeast Asian pachychilids, with a viviparid or two thrown in for diverse measure.  Quoting Ting Hui directly, “The rarity of the species may drive increased demand, which may ultimately lead to a decline of the species.”

So what evidence might there be to suggest that hobbyists or collectors might drive populations of gastropods such as these to extinction by overharvest?

The discipline of fisheries management is generally considered to have been born in the early 1930s, with the development of the concept of maximum sustained yield [4].  Stated simply, MSY = Kr/4, where K is the carrying capacity of the environment, and r the intrinsic rate of natural increase.  These are difficult and near-impossible parameters to estimate, respectively, and so the concept of MSY has rarely seen application, even in the management of the most commercially valuable fisheries.  Much less snails.

But, if you’ll allow Captain Obvious to take the helm here, note that the concept of MSY depends on the assumption of density-dependent population regulation.  And, to be quite frank, as your Captain always is, it is my strong impression that essentially all our colleagues with research interests in the ecology of mollusk populations, or indeed with interests in any aspect of the biology of any invertebrate population whatsoever worldwide, carry with us a (near-universally unstated) assumption of density-independence.  In other words, we assume that the size of our study populations is not a function of r and K, but of extrinsic factors such as weather, or floods, or harvest by Indonesian locals who might want to gather up a few small but exotic-looking snails from the lakeshore to sell to feed their families. 

Well, shame on us all.  The tiny little scraps of evidence available today suggest that the regulation of freshwater gastropod populations is as density-dependent as any population of living things on this earth.  The figure below, reproduced from Chapter 5 of my (2000) book, shows the densities of five freshwater gastropod populations over records of 5 – 10 years.  My PBLR test on the longest record available (the Ancylus data set of Russell-Hunter) returned a value of t significant at the 0.01 level, showing strong evidence of density-dependent regulation [5].

Dillon (2000) Figure 5.11
The grand mean density of the Ancylus population in the stream studied by Russell-Hunter, 260 per square meter, can therefore be taken as a rough estimate of carrying capacity.  The grand means of the other populations (per meter squared) were Physa = 77, Lymnaea = 93, Hydrobioides = 41, and Pomacea = 0.11.  The Pomacea estimate did not include juveniles, however.  Shall we take, as a rough estimate of carrying capacity K for freshwater gastropod populations, about 10 per square meter?

Table 5.1 of my (2000) book offers a big compilation of demographic data for 36 populations of freshwater gastropods [5].  The median value for intrinsic rate of natural increase tabulated was around r = 1.5, but the two prosobranch values were systematically lower, just r = 0.09 for Pomacea and r = 0.24 for Melanoides.  Then if we roughly estimate the value of r for freshwater prosobranch populations as r = 0.1 per generation, and carrying capacity K = 10 per square meter, we find MSY = Kr/4 = 0.25 snails per square meter per generation.

My biological intuition suggests that Tylomelania probably mature at around age one year and reproduce continuously thereafter. And the surface area of Sulawasi’s Lake Pozo, where all the Tylomelania live, is approximately 300 square km.  I realize all the lake bottom is not equally inhabitable by snails, but you get the picture.  Back-of-the-envelope estimates suggest that any subtraction of snails by collectors from the Tylomelania populations of Lake Pozo below roughly 10 million snails per year will not ultimately lower the population size, but will be replaced.  And there is zero evidence suggesting otherwise. 

OK, I understand the justification.  My colleagues want grant funding to gather hard data on the size and demographics of Tylomelania populations, so that an informed decision can be made.  In the meantime, since we don’t know, we must err on the side of caution, yes?  Well, I agree with that first sentiment, but not the second one.  Science does not make recommendations based on the premise, “Since we don’t know.”  I understand the fear, but fear is not reason.  Fear is the opposite of reason.

The chairman of my graduate committee 1977 – 1982 was a prominent ecologist named Dr. Robert E. (Bob) Ricklefs.  At some point in my graduate career, he made a point that has stuck with me for 40 years.  Bob observed that if we assume population size is a function of density-independent effects, populations are like drunks on a subway platform, veering left and right randomly until they either go extinct or cover the earth ass deep.  I realize that sometimes it seems extinction is frighteningly common.  But if the size of freshwater gastropod populations were indeed a function of density-independent factors [6], the two phenomena (extinction and ass-deep-coverage) would be equally common, with the frequency of extinction = frequency of coverage = 0.50.  Since that is not the case, density-dependence must prevail.

Well, we’ll return to that ass-deep-earth-coverage thing next month.  But the bottom line for today is that there is no evidence that natural populations of mollusks can be driven to extinction by the love of hobbyists [7].  And a lot of evidence that the love of hobbyists can be beneficial to the work of science.  The birdwatchers are a tremendous asset to ornithology, and the stargazers a tremendous asset to astronomy.  Indeed, the vibrant amateur communities of birders and gazers are where the professional ornithologists and astronomers are born. 

Meanwhile we malacologists are so wrapped up in the remote likelihood that our study organisms might disappear into extinction that we cannot see the imminent extinction of our own profession.  And I strongly suspect the attrition rate in the halls of malacology has been well above Kr/4 for quite a few generations now.


[1]  I myself was not called to the AMS Council until 1999.  I did campaign heavily for repeal of the shell ban during my 2001-02 presidency, but could not find the votes.  The best I could do was neglect the issue entirely when I redrafted the AMS constitution & bylaws 2002-03.

[2] What’s Out There? [9Oct17]

[3] Ng Ting Hui, Tan SK, Wong WH, Meier R, Chan S-Y, Tan HH, Yeo DCJ (2016) Molluscs for Sale: Assessment of Freshwater Gastropods and Bivalves in the Ornamental Pet Trade. PLoS ONE 11(8): e0161130. https://doi.org/10.1371/journal.pone.0161130

[4] Russell, E. S. (1931). Some theoretical Considerations on the "Overfishing" Problem. ICES Journal of Marine Science. 6 (1): 3–20.
Graham, M. (1935). "Modern Theory of Exploiting a Fishery, and Application to North Sea Trawling". ICES Journal of Marine Science. 10 (3): 264–274.

[5]  Dillon, R. T., Jr. (2000) The Ecology of Freshwater Molluscs.  Cambridge University Press.  All the details for the demographic analyses referenced above are found in Chapter 5, with the material on carrying capacity pp 202 – 207, and intrinsic rate of natural increase on pp 172 – 182.

[6] Or if such populations could be driven to extinction by harvest rates very much above Kr/4.

[7] In fact, it seems unlikely to me that even unregulated commercial harvest could drive marine shellfish populations to extinction.  And I don’t think there’s any evidence that the pearl-button industry was responsible for any of the freshwater mussel extinctions.  The only cases of human overharvest I’ve ever heard of, for any mollusk population in any environment whatsoever, are the occasionally-successful handpicking efforts to control land snail pests.  See:

Simberloff, D. 1997. Eradication. Pages 221–228 in D. Simberloff, D. C. Schmitz, and T. C. Brown, editors. Strangers in paradise. Island, Washington, D.C., USA.

Monday, October 9, 2017

What's Out There?

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023c)  What's Out There?  Pp 23 – 28 in The Freshwater Gastropods of North America Volume 7, Collected in Turn One, and Other Essays.  FWGNA Project, Charleston, SC.

Last summer an interesting paper came across my desk – so interesting, in fact, that I filed it in my stack of promising subject matter for the FWGNA blog.  Where it was promptly buried.  But from which this week it has been exhumed, to stimulate my imagination afresh.

The paper is entitled, “Molluscs for sale: Assessment of freshwater gastropods and bivalves in the ornamental pet trade [1].”  The senior author, Ting Hui Ng, and her six coauthors hail almost exclusively from Singapore, the primary exporter of ornamental fishes to the global marketplace.  Ting Hui and her colleagues surveyed seven local retail shops and major aquarium-stock exporters between 2008 and 2014, documenting an impressive 47 species of freshwater gastropods and 12 species of bivalves available for sale to the hobby worldwide.  Of the gastropods, the authors considered 26 to be oriental in their origin, 7 Australasian, 4 Neotropical, and 1 North American, leaving 9 classified as “cosmopolitan.” 
Figure 1 of Ng et al. (2016)
The entire malacological zoo is depicted in the author’s Figure 1 reproduced above, with their (extensive) caption copied at note [2] below.  I hate to fuss [3], but the scales are completely messed up in this figure – not just the unmarked scale bars (which are supposed to be 10 mm) but the scale bars “indicated differently.”  With regard to the actual sizes of any of these 59 creatures, you are on your own.

The single North American species was identified as “Physa sp.”  I would have bet dollars-to-donuts that this must be Physa acuta, the world’s most cosmopolitan freshwater snail [4], which is indeed widely introduced into the waters of Singapore, until I swapped emails with Ting Hui. She called my attention to her 2015 paper reporting the discovery of a single individual physid in a Singapore aquarium shop, and a second individual in Malaysia, 22% different from anything in GenBank [5].  I'm going to fight the temptation to digress here, but see note [6] below.

The main point is that Physa (and three other gastropod species) were classified as “hitchhikers” by Ting Hui and colleagues, which means that they were discovered in Singapore incidentally transported with aquatic plants, ornamental fish or other freshwater mollusks, and not literally “For Sale,” because nobody wants them.  But at least North America wasn’t skunked entirely.  USA!  USA! USA!

The four Neotropical species were all (you guessed it) ampullariids – Pomacea canaliculata, Pomacea maculata, Pomacea diffusa, and Marisa cornuarietis.  All these various South American ampullariids are also quite familiar to us here in the USA, introduced years ago into Florida and Texas, recently knocking on our doorsteps in South Carolina [9].

Among the remainder of the gastropods for sale in Singapore, I myself was most interested by the strange and exotic-looking pachychilids and thiarids.  We are certainly familiar with #48 Melanoides tuberculata here in the USA [10].  But I was surprised not to see the oriental Tarebia granifera in the gallery compiled by Ting Hui and her colleagues.  Tarebia has been introduced to several southern US states and is sporadically common in Central America and on many Caribbean islands [11].

And speaking of noteworthy absences.  Neither Bellamya japonica nor B. chinensis appears on Ting Hui's list of 59.  I’m sure their mothers must love them, but perhaps Bellamya are too plain and clunky to find a market among aquarium hobbyists?  Or has Bellamya become so common here in North America [12] that nobody buys them out of Singapore?  It has always been my impression that they are marketed here in the USA primarily by suppliers to the backyard “water garden” trade, along with koi, water lilies, and little tumbling fountains.  Not the (indoor) aquarium shops supplied by Singapore.

The research interests of Ting Hui and colleagues seem to have been motivated by two primary concerns – that exotic freshwater mollusks might spread, and that they might not.  Let’s set aside the former concern for the time being, and focus on the latter.

Eight of the 59 freshwater mollusk species for sale in Singapore were identified by Ting Hui as “narrowly-endemic.”  These included the three spiny species of Brotia, the four Tylomelania species, and the viviparid Celetaia persculpta.  Quoting directly from Ting Hui: 
“These species appeared to fetch higher prices compared to more common species (up to US$10 per individual Tylomelania sp. compared to US$5 per individual Thiaridae or Neritidae, THN pers. obs.). The rarity of the species may drive increased demand, which may ultimately lead to a decline of the species.”
Pachychilid snails of the genus Brotia are ovoviviparous but sexually reproducing – males and females apparently present in equal frequency.  Brotia armata (#34) and B. binodosa (#35) are members of what Glaubrecht & Kohler called a “species flock” in the Kaek River of central Thailand [13]Brotia pagodula (#37) is endemic to the Salween River and its tributaries on the border of Thailand and Myanmar.   Their habitat is given as “Attached to rocks in sectors with swift currents” [14]

The genus Tylomelania (#39 - 42) is another group of ovoviviparous pachychilids, these endemic to particular lakes, rivers, and streams on the Indonesian Island of Sulawesi.  Our friends Thomas von Rintelen and Matthias Glaubrecht recognized 62 species of Tylomelania the last time I checked, but I haven’t been home since morning [15].

So the paper by Ting Hui and colleagues opened with this sentence: “The ornamental pet trade is often considered a key culprit for conservation problems such as the introduction of invasive species (including infectious diseases) and overharvesting of rare species.”  Can a gastropod population – especially a population endemic to some narrowly-circumscribed patch of habitat – indeed be threatened by overharvest?  What is the evidence that hobbyists can drive populations of their favorite organisms to extinction with love?  Tune in next time.


[1] Ng Ting Hui, Tan SK, Wong WH, Meier R, Chan S-Y, Tan HH, Yeo DCJ (2016) Molluscs for Sale: Assessment of Freshwater Gastropods and Bivalves in the Ornamental Pet Trade. PLoS ONE 11(8): e0161130. https://doi.org/10.1371/journal.pone.0161130

[2] Fig 1. Freshwater molluscs in the ornamental pet trade.
Unless indicated differently, scale bars = 10mm. 1. Batissa similis; 2. Batissa violacea; 3. Corbicula fluminea; 4. Corbicula moltkiana; 5. Hyriopsis bialata; 6. Hyriopsis desowitzi; 7. Parreysia burmana; 8. Parreysia tavoyensis; 9. Pilsbryoconcha exilis; 10. Scabies crispata; 11. Sinanodonta woodiana; 12. Unionetta fabagina; 13. Marisa cornuarietis; 14. Pomacea canaliculata; 15. Pomacea diffusa; 16. Pomacea maculata (photograph by K.A. Hayes); 17. Bithynia sp.; 18. Clea bockii; 19. Clea helena; 20. Radix rubiginosa; 21. Clithon corona; 22. Clithon diadema; 23. Clithon lentiginosum; 24. Clithon mertoniana; 25. Neripteron auriculata; 26. Neritina iris; 27. Neritina juttingae; 28. Neritina violacea; 29. Neritodryas cornea; 30. Septaria porcellana; 31. Vittina coromandeliana; 32. Vittina turrita; 33. Vittina waigiensis; 34. Brotia armata; 35. Brotia binodosa; 36. Brotia herculea; 37. Brotia pagodula; 38. Sulcospira tonkiniana; 39. Tylomelania towutica; 40. Tylomelania sp.; 41. Tylomelania sp.; 42. Tylomelania sp.; 43. Physa sp.; 44. Amerianna carinata; 45. Indoplanorbis exustus; 46. Gyraulus convexiusculus; 47. Semisulcospira sp.; 48. Melanoides tuberculata; 49. Stenomelania offachiensis; 50. Stenomelania plicaria; 51. Stenomelania cf. plicaria; 52. Stenomelania sp.; 53. Thiara cancellata; 54. Celetaia persculpta; 55. Filopaludina cambodjensis; 56. Filopaludina peninsularis; 57. Filopaludina polygramma; 58. Sinotaia guangdungensis; 59. Taia pseudoshanensis.

[3] No, I don’t.

[4] Dillon, R. T., A. R. Wethington, J. M. Rhett and T. P. Smith.  (2002)  Populations of the European freshwater pulmonate Physa acuta are not reproductively isolated from American Physa heterostropha or Physa integra.  Invertebrate Biology 121: 226-234.

[5] Ng, TH, SK Tan, & DCJ Yeo (2015) Clarifying the identity of the long-established, globally-invasive Physa acuta Draparnaud, 1805 (Gastropoda: Physidae) in Singapore.  BioInvasions Records 4: 189 - 194.

[6]  This is fascinating.  It is certainly possible that the 22% CO1 sequence difference reported in Singapore is another case of mitochondrial superheterogeneity, which (we do know) occurs in North American populations of Physa acuta, almost certainly a signature of cytoplasmic male sterility [7].  It is also possible that the "Physa sp" reported by Ng and colleagues in Singapore might indeed be a distinct biological species.  Over and over again, all over the world, we have seen invasions by species mixtures, which have been sorted out only at the site of introduction, and then subsequently corrected in their places of origin.  I do think it is possible that the American Pacific northwest may be inhabited by a species perhaps best identified as Physa concolor, but called Physa natricina in the Snake River, morphologically very similar to Physa acuta, but reproductively isolated from it [8].  Is this Physa concolor in Singapore?  Wild speculation here, but who knows?  Science is lots of fun, isn't it?

[7] For more on mtSH in Physa, see:
  • Cytoplasmic Male Sterility in Physa! [9June22]
[8] For more on what I called "Hypothesis #2 (of 3) See:
  • The Mystery of the SRALP: A bidding [5Feb13]
[9] I’ve published quite a few essays on the North American Pomacea invasion.  See:
  • Pomacea spreads to South Carolina [15May08]
  • Two dispatches from the Pomacea front [14Aug08]
  • Pomacea news [25July13]
[10] For more on the North American populations of Melanoides, see:
  • To only know invasives [16Oct15]
  • The many invasions of Hilton Head [16Dec15]
[11] Pointier, J-P., R. Incani, C. Balzan, P. Chrosciechowski, and S. Prypchan (1994)  Invasion of the rivers of the littoral control region of Venezuela by Thiara granifera and Melanoides tuberculata and the absence of Biomphalaria glabrata, snail host of Schistosoma mansoni.  Nautilus 107: 124 – 128.

[12] For more on Bellamya in North America, see:
  • Bellamya News [6Oct05]
  • Community consequences of Bellamya invasion [18Dec09]
  • Just before the bust [5Aug14]
[13] Ng and colleagues recorded only 0.5% uncorrected pairwise 16S sequence difference between their individual B. armata and B. binodosa analyzed.  Hmm…

[14] Kohler, F, and M. Glaubrecht (2006)  A systematic revision of the southeast Asian freshwater gastropod Brotia (Cerithioidea: Pachychilidae)  Malacologia 48: 159 – 251.

[15] von Rintelen T., B. Stelbrink, R. M. Marwoto, & M. Glaubrecht (2014) "A Snail Perspective on the Biogeography of Sulawesi, Indonesia: Origin and Intra-Island Dispersal of the Viviparous Freshwater Gastropod Tylomelania". PLoS ONE 9(6): e98917.

Wednesday, September 6, 2017

Not Finding Fontigens cryptica

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019c) Not finding Fontigens cryptica.  Pp 245 - 250 in The Freshwater Gastropods of North America Volume 3, Essays on the Prosobranchs.  FWGNA Press, Charleston.

In July we met Mrs. Lori Schroeder, the remarkable amateur malacologist dedicated to surveying the gastropod fauna of the Bernheim Arboretum and Research Forest south of Louisville, Kentucky.  And In August we convinced ourselves that the tiny hydrobiid shells Lori discovered in debris washed along the banks of Harrison Creek were best identified as those of Fontigens cryptica, The Most Cryptic Freshwater Gastropod in The World [1].

But as of the spring of 2017, neither Lori, nor her colleagues, nor indeed a team of professional karst, cave, and groundwater biologists had found a single living Fontigens anywhere on the Bernheim property.  It was the expert opinion of Dr. Jerry Lewis that populations of Fontigens cryptica are obligately restricted to interstitial spaces in waters flowing through subterranean beds of sand and gravel, equally unlikely to be recovered from creek waters at the surface and from cave waters below.

Removing the mesh trap from a drainage pipe.

One of the many charming gags in the 1987 Hollywood movie, “The Princess Bride” is a scene where our hero and the bad guy wage a battle of wits involving a poison called iocane [2].  Iocane is odorless, colorless, and tasteless.  So the contest begins when our hero brandishes a vial of poison in front of the bad guy, challenges him to put the vial to his nose, and says, “What you’re not smelling is iocane.”

By some similar logic, I myself felt called to not see what everybody else was not seeing in the caves, springs and streams of central Kentucky.  And I also wanted to survey the complete freshwater gastropod fauna of Bernheim, not just its rarest element.  And I also very much wanted to meet my remarkable colleague, Lori Schroeder.

Note the meticulous labels
And on Saturday, 17June17, I was not disappointed at any of the three elements of my quest.  Lori and her husband Jeff met me in the Bernheim parking lot with smiles and greetings and a fresh pink & green gift bag.  And in the bag were four matching Tupperware containers.  And in one of those containers [3] were four zip lock bags.  And in each of those bags was a vial, and in each vial a meticulously-documented and beautifully formatted label and a clear pill capsule, and in each pill capsule a sample of tiny snails.

We started at Lake Nevin, right by the entrance gate.  No, of course we weren’t expecting to discover any Fontigens in a small lake impounded for landscaping purposes.  Poking around in the margins of Lake Nevin I was trying to do something else it probably isn’t possible to do – overtly correct for a known bias.

Normal sampling processes, such as the ordinary methods ecologists use to sample biological communities, are biased against rare species.  Any element with a relative abundance of less than one will be recorded as a zero.  The FWGNA databases show the opposite trend, however.  Number theoretical analysis has suggested that our lists of North American freshwater gastropods are biased for rare species, not against [4].

Longtime readers of this blog are aware that I occasionally preach little sermons [5] about a phenomenon I call “conservation-biased oversampling.”  This is the tendency, quite unapologetic in many published surveys and vivid in the systematic collections held by major museums, for researchers to focus their sampling efforts on species that they think are rare or endangered.  Such efforts, driven by the availability of research funding and the quest for more, are ultimately counter-productive.

So as of 17June17 I was carrying on the hard drive of my computer data documenting three locations where Lori had recovered shells of Fontigens cryptica in the Bernheim Arboretum and Research Forest.  And not one single datum regarding any population of any trash pulmonates that might be inhabiting the property whatsoever.  Which I felt powerfully called to fix.

And such a fine field companion was Lori Schroeder!  So enthusiastic, so interested, so eager to learn.  I got a fist-bump for a limpet.  At one point about mid-morning I was poking around in the backwater of some little stream, pulled up a dead leaf, and found a single Ferrissia fragilis adhering to the underside.  Lori was so excited that she jumped up, gave a little whoop and offered me a fist-bump.  For a plain brown limpet, probably not 4 mm in maximum extent.  A human behavior unprecedented in my long experience.

What a beautiful day, what a lovely part of the world, and what excellent company!  Lori and Jeff guided me to every spring, stream, lake and pond on the Bernheim property, plus a wide assortment of bone-dry creek beds, obscure holes in the ground, and forsaken dunes of dusty organic debris.  We rode up and down the rich old fields of the Harrison Creek valley in the back of Jeff’s pickup truck, checking that series of mesh traps Lori and Jeff had wired onto the drainage pipes in March.

The picnic spread that Lori and Jeff set was spectacular.  In my ordinary life, the only time I ever eat roast beef and ham together is Christmas, maybe.  Lori offered 5 – 6 types of meats and cheeses and 10 – 12 Tupperware boxes filled with an assortment of ice-cold fruits and veggies.  And I’ve got to say, that cold bottle of Kentucky’s indigenous “Ale 8” ginger ale was among the finest things I can ever remember wrapping my lips around.
The cool, clear waters of Harrison Creek sparkled like jewels on that sun-dappled afternoon, a nice population of Pleurocera semicarinata grazing lazily across the horizontally-bedded shelves of limestone.  There wasn’t much debris of any sort in the stream, nor indeed even loose rock, cobble, or cover of any description.  At one point I stopped and looked around myself and counted, from a single vantage point, 82 crayfish.  And I paused to reflect on the selective forces that might drive a freshwater gastropod population into subterranean life – to quit competition for the rich periphyton resources potentially available in such a stream and adapt to the meager rations of the lightless hyporheic zone.

No, we did not find any Fontigens cryptica on that long, fine day at Bernheim [6].  Last I heard, Lori and Jeff were talking about assembling a Bou-Rouche sampling device from the materials available at the local Tractor Supply Company, basically a piston pump driven into the creek bed, to continue the quest.

But in my personal opinion, the world already has enough populations of pale, white, 2 mm snails crawling through interstitial spaces deep in our subterranean gravel deposits.  What this world needs is more Lori Schroeders. 


[1] My previous posts in this series:
  • Lori Schroeder’s Tiny Snails [17July17]
  • The Most Cryptic Gastropod in The World [6Aug17]
[2] The battle of wits from The Princess Bride [YouTube]

[3] If you’re curious, the other Tupperware containers held a big honkin’ Campeloma from nearby Beech Fork River, a sample of Pleurocera and Physa from nearby Sunfish Creek, and a sample of Pleurocera and Campeloma from The Land Between The Lakes.

[4]  See the analysis of species richness in my overall Synthesis of the FWGNA Atlantic drainage data here: [FWGNA Synthesis]

[5] I coined the term “conservation-biased oversampling” in my post of 19Mar12, and touched on it again 6Jan14 and 16Oct15.  See:
  • Toward the Scientific Ranking of Conservation Status – Part III [19Mar12]
  • Why Is Rarity? [6Jan14]
  • To Only Know Invasives [16Oct15]
[6] Our complete list of 17June17:  Found everywhere = Physa acuta, Menetus dilatatus, and Lymnaea humilis.  Found in the lakes and ponds = Lymnaea columella, Gyraulus parvus, and Helisoma trivolvis.  Found in the creeks = Pleurocera semicarinata semicarinata, Physa gyrina, Ferrissia rivularis, and Ferrissia fragilis (outside the gate).

Sunday, August 6, 2017

The Most Cryptic Freshwater Gastropod In The World

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019c) The most cryptic freshwater gastropod in the world.  Pp 241 - 244 in The Freshwater Gastropods of North America Volume 3, Essays on the Prosobranchs.  FWGNA Press, Charleston.
L. Hubricht [3]

Through much of the 20th century, the #1 (and possibly only) expert in the biologically fascinating genus Fontigens was the legendary Mr. Leslie Hubricht (1908 – 2005).  Hubricht was trained as a repairman for adding machines and (later) for computers, but spent most of his life travelling around the United States in a van, digging through humus, rolling logs, and peering into holes [1].  He published over 150 scientific papers, primarily on land snails but also on the biota of caves.  Among these were 4 - 5 papers on spring or groundwater-dwelling hydrobiid snails, especially Fontigens [2].

So last month I shared an inspiring story about Lori Schroeder and her discovery of the tiny shells of a mysterious Fontigens species in deposits of storm water flotsam on the margins of several creeks at the Bernheim Forest in central Kentucky [4].  And I mentioned in passing that our good friend Bob Hershler, together with Leslie Hubricht and the cave biologist John Holsinger, had listed nine “recognized species” of Fontigens in their 1990 monograph [5].  Let me back up and expand that statement slightly.

Hershler and his colleagues actually listed ten species, nine of which they “recognized” and one of which was of “questionable status.”  That tenth species, mentioned in a single concluding paragraph on page 43, was Fontigens cryptica.

Leslie Hubricht described Fontigens cryptica in 1963 from under stones in a small spring along the Ohio River in southeast Indiana [6].  He seems to have had at least one living specimen in hand, because he described the animal as “translucent whitish, blind.”  But he immediately confessed, “verge unknown.”  Hershler reported in 1990 that he “was unable to find the snail during two recent visits to the type locality (and nearby localities), nor was it taken during an extensive survey of subterranean habitats in the region (Lewis 1983).”  Hence the uncertainty of its status.

Below I have scanned the 1.9 mm holotype figured by Hubricht in 1963 next to a photo of a 1.9 specimen collected last year by Lori Schroeder.

Notice also the reference to a "Lewis 1983" in the Hershler quote reproduced above.  My attention was called to the existence of this tenth, questionable-status Fontigens by none other than Dr. Julian J. Lewis himself, still very active in karst, cave, and groundwater research in Kentucky today.

By one of those strokes of fortune I have begun to take for granted in my long career, it materialized that in 2016 the Bernheim management engaged Lewis and Associates LLC to survey the subterranean fauna of its caves and springs, and that professional surveys of the entire property had been underway for several months prior to the date that Lori Schroeder first brought her Fontigens discovery to my attention.

So in April Lori offered me an electronic introduction to Dr. Julian (Jerry) Lewis, and we struck up a conversation.  And Jerry confirmed: 
“Bob Hershler and I looked for this species together at the type-locality at a spring in Clark County, Indiana and I've been there repeatedly with no luck.  The spring is high on a bluff overlooking the Ohio River and consists of a hole about the size of one's fist....not much habitat in which to search.  Subsequently I pulled shells of this species from a meter below the surface of the Blue River  -  from groundwater flowing through the hyporheic zone, in the company with a number of other non-cave subterranean species - using a Bou-Rouche sampling pumpwell. 
 I found the snails alive in the interstices of a gravels in a similar situation in a cave in Monroe County, Indiana (near Bloomington) using Karaman-Chappuis extraction. 
 So I suspect your snails are probably a groundwater species, likely living in the interstices of gravel and sand, and will require special sampling methods."
So no, Lewis and Associates LLC had not recovered any Fontigens whatsoever in their survey of the Bernheim property just recently concluded as of this spring [7].   Nor indeed was it Jerry’s expert opinion that we should expect to find any.  Jerry’s studies of the entire regional biota have led him to hypothesize the existence of a single subterranean zoogeographic province extending at least as far south as Mammoth Cave in central Kentucky and as far north as the Blue River drainage of Indiana.  But he has never seen a population of Fontigens cryptica in any cave stream he has explored, ever.  Gravel under a cave stream, yes.  But the little snail is no more an inhabitant of open flowing water under the ground than of open flowing water at the top.  Fontigens cryptica seems to be limited to a third, even more mysterious habitat: saturated interstitial spaces.

I concluded last month’s blog post with a series of three teaser questions: “From what dark recesses of central Kentucky knobland might Lori’s tiny little snails be emanating?  And what might be their identity?  And will Lori Schroeder surrender her quest?”  This month I have addressed questions #1 and #2.  Next month I will address #3.  And here’s your teaser.  No.


[1] He stood silently in the lobby outside AMU meetings in the 1970s and 1980s, wearing a stiff dark suit.  I wish I had gotten to know him.

[2]  Gerber, J. (2010)  Leslie Hubricht (1908 – 2005), His publications and new taxa.  American Malacological Bulletin 28:15-27.

[3] The image of Leslie Hubricht reproduced above is a detail from a group photo of the American Malacological Union taken in Columbus, Ohio, in 1976.  For a larger version, see:
  • Bill and Ruth and Jack and Virginia, and Campeloma [5Apr21]
[4] Lori Schroeder’s Tiny Snails [17July17]

[5] Hershler, R., J. R. Holsinger and L. Hubricht (1990)  A revision of the North American freshwater snail genus Fontigens (Prosobranchia: Hydrobiidae).  Smithsonian Contributions to Zoology 509: 1 – 49.

[6] Hubricht, L. (1963)  New species of Hydrobiidae.  Nautilus 76: 138 – 140.

[7] Only a single freshwater gastropod was listed among the 61 species documented by Lewis and Associates - Lymnaea humilis in a seep spring.

Monday, July 17, 2017

Lori Schroeder's Tiny Snails

Mrs. Lori Schroeder manages her husband’s dental practice in Bardstown, Kentucky.  She is also a skilled and dedicated malacologist, who in recent years has expanded her interests from seashells to land snails and into the freshwater fauna.  Back in 2009 she volunteered to lead a “Bioblitz” survey of the land snails of the Bernheim Arboretum and Research Forest south of Louisville [1], collaborating with our good friends Harry Lee, the late Henry McCullagh and Bill Frank [2].  And several years ago I was blessed to strike up a correspondence.

Organic litter by Harrison Creek
Lori’s favorite method of surveying land snails is to pick through samples of forest litter, such as are often deposited along the courses of the several creeks and streams running through the 15,000 acre Bernheim property.  So it is not surprising that she occasionally finds freshwater gastropods mixed with her land snail collections.  I received my first emails from her in 2013 regarding the pleurocerids and physids of Bernheim, which I was pleased to entertain.

And I was pleased to receive another email from Lori this past January.  She sent to my attention a jpeg photo of a small planorbid, requesting guidance on the difference between Menetus and Gyraulus.  And, as an afterthought in some follow-up correspondence, she mentioned, “I also have a tiny unidentified hydrobiid species from the same lot.”

My antennae raised immediately.  I replied, “What’s this I hear about a tiny unidentified hydrobiid?  I’d be curious to see a photo of that one as well.”  And on 1 February 2017, this is the jpeg Lori sent me:

My antennae raised even higher.  Clearly a little pile of Fontigens, that diminutive inhabitant of springs, spring runs, and caves scattered widely throughout the Eastern and Midwestern United States.  I reached to the shelf beside my desk and pulled out my well-thumbed copy of the monograph by our good friend Bob Hershler and colleagues [3].  And here is the reply I sent Lori, under the subject line “OK, now you’ve got my attention:”
Dear Lori, 
The jpegs attached to your message of earlier this afternoon appear to depict a hydrobiid population of the genus Fontigens.  My first guess would be the most common species, Fontigens nickliniana.  But upon closer examination, they might look more like published photos of Fontigens aldrichi, which I’ve never personally seen on the hoof.
The genus Fontigens was marvelously-well monographed by Bob Hershler and colleagues (1990).  And among the many surprises is that Hershler did not report any records of Fontigens of any species in Kentucky, period.  F. nickliniana is widespread in the Great Valley of Virginia, spreading up to Pennsylvania, and also in western Michigan, so one might assume that they range through Kentucky.  A lot of secondary references do indeed list F. nickliniana in your state.  But I myself have never seen a F. nickliniana population in Kentucky, and don’t know of any reliable record.
All that said, the flat nuclear whorl doesn’t really look like F. nickliniana.  Picture-matching to the other eight species recognized by Hershler, they look more like Fontigens aldrichi or Fontigens antroecetes.  But those species are not known outside of Missouri.
Bottom line.  Those shells were all dead-collected, am I right?  It would be great if you could find the living population, and send a preserved sample to Bob Hershler at the USNM.  Fontigens populations are often narrowly-restricted to springs and spring runs.  There’s a lovely, clean, clear, coldwater spring right upstream from your collecting site, am I correct?  Lots of watercress, I’ll bet?  You should find your big population of Fontigens at that spring head, covering the cress and every square inch of bottom.  Go look and tell me if I’m right.  Take a Nalgene bottle or something to collect in.
Standing by,
And here is Lori’s immediate reply: 
Hello Dr. Dillon, 
I've been down the hydrobiid road with Dr. Lee and Dr. Fred Thompson at the Florida Museum previously [4].  I failed miserably to locate any living specimens.  That being said, I am more than willing to give it a second go. 
 It subsequently materialized that my speculations about a spring head with “lots of watercress” and “Fontigens covering every square inch of bottom” were very, very wrong.  And the situation much more complicated than I initially imagined.

Lori had found her little pile of Fontigens shells sorting through debris deposited along Harrison Creek by a catastrophic flood that ravaged the area in January of 2016.  Harrison Creek washes down through a lovely valley of old fields flanked by mixed hardwoods.  Yes, there are (indeed) small springs and caves on the ridges surrounding, but most issue water only in wet weather.

A further complication was that Lori had actually found Fontigens shells in similar circumstances along three different streams on the Bernheim property during the course of her extensive studies of the area, all in dry debris deposited by floodwaters, none downstream from any spring or other obvious source of groundwater.

And on 3 February 2017 Lori sent me another set of more detailed jpegs, giving a standard shell length of just 2.1 mm.  Adult F. nickliniana reach 3 – 4 mm, in my experience.

Broadly speaking, there are two categories of Fontigens in North America, which (given my Presbyterian heritage) I think of as being either “black” or “white” [5].  The black species, such F. nickliniana, F. morrisoni and F. bottimeri, are usually somewhat larger and live above ground.  The white species, such as F. orolibas, F. tartarea and F. turritella, are usually smaller and subterranean.  The shell photos Lori sent us on Feb 3 struck me as depicting a white species – not something we might expect to find at the surface.

Undaunted, Lori and her husband Jeff set out on what she called a “full-on blitz attack,” ultimately extending over several months and involving Andrew Berry, Forest Manager at Bernheim.  And I cannot remember ever witnessing, first-hand or second, a more earnest or comprehensive survey of any patch of the earth for any mollusk population, of land or sea.  Lori and colleagues surveyed every spring or cave or hole in the ground actually, potentially, or historically upstream or in the vicinity of every location where any Fontigens specimen had ever been recovered from Bernheim.  They also installed mesh traps over the openings of several culverts draining into Harrison Creek.  And the results, to quote Lori directly, were “Nothing.  Nada.  Zilch.”

From what dark recesses of central Kentucky knobland might Lori’s tiny little snails be emanating? Indeed, what might be their identity?  And will Lori Schroeder surrender her quest?  Tune in next time! 


[1] The Bernheim Arboretum and Research Forest was originally developed in 1929 and endowed by the German philanthropist Isaac W. Bernheim “as a gift to the people of his new homeland.”  It is open to the public during regular daylight hours, with a small admission charge on the weekends.
Website: [html]

[2] The Kentucky land snail list is available at [Jaxshells-Kentucky].
Photos of many elements of the Bernheim freshwater gastropod fauna are also available from the jaxshells.org website, if you try the search button at the bottom of the front page.

[3] Hershler, R., J. R. Holsinger and L. Hubricht (1990)  A revision of the North American freshwater snail genus Fontigens (Prosobranchia: Hydrobiidae).  Smithsonian Contributions to Zoology 509: 1 – 49.

[4] Yes, it materialized that the 2016 specimens were not the first Fontigens Lori had found in her nine-year survey of Bernheim.  Several years previous she had corresponded briefly with Fred Thompson about the little snails, but Fred was not interested unless she could find live material, and the matter dropped.

[5]  For an illustration of the striking black/white dichotomy see:
  • Springsnails of The Blue Ridge [26July06]

Tuesday, June 27, 2017

The Freshwater Gastropods of The Ohio: An Interim Report

By popular demand!  Several of you have requested copies of the presentation I contributed at the Society for Freshwater Science meeting in Raleigh earlier this month.  A pdf download is available for the clicking below.

My collaborators on the work were Ryan Evans of KYDOW, Mark Pyron of Ball State, Tom Watters of Ohio State, Will Reeves of the USDA in Ft. Collins, Richard Kugblenu of SUNY-Albany, and Jeff Bailey & Mike Whitman of WVDEP.  Here’s the abstract: 
We report preliminary results from a survey of the freshwater gastropod fauna from the Ohio River basin above Paducah, including western Pennsylvania and most of West Virginia, Ohio, Kentucky, and Indiana.  Our database of 4,746 records was almost entirely drawn from state natural resource agencies (36%), museums (30%) and our own original collections (30%), almost all personally examined and verified.  We report 66 species and subspecies of freshwater gastropods [1], the most common of which are Physa acuta (959 incidences), Ferrissia rivularis (536), and Pleurocera semicarinata (all subspecies combined 528).  Nine species were collected in but a single population, four of which seem to be legitimately rare, the remainder peripheral.  The distribution of commonness and rarity appeared log-2 bimodal, with mean 3.84 (14.3 incidences) and standard deviation 2.79 (6.9 incidences).  Our Ohio River basin results are compared to similar databases previously assembled from the Atlantic drainages and from East Tennessee, and the 99 species of the combined 13-state fauna ranked by their incidence.
 I should emphasize that the results as I offered them in Raleigh were very preliminary.  Subsequent to the submission of the abstract above, our GIS analysis suggested that a couple subregions of our study area had been oversampled, resulting in a prune of our database back from 4,746 records to 4,570.  And I have just returned from two weeks in the field, adding quite a few sample sites from northern Tennessee [2] and central Kentucky, as well as a very large and impressive slug of data from Illinois [3].

Several of you have also asked me when the finished FWGO site might be expected to appear online.  That date, to be precise, is Not Quite Yet.  But we’ll keep you posted… 


[1] We recognize 6 subspecies of freshwater gastropods in the FWGO study area: the pair Campeloma decisum crassulum and C. decisum (ss), the pair Pleurocera simplex ebenum and P. simplex (ss), the pair Pleurocera canaliculata acuta and P. canaliculata (ss), the pair Pleurocera laqueata alveare and P. laqueata (ss), and the trio Pleurocera semicarinata livescens, P. semicarinata obovata, and P. semicarinata (ss).  Thus the total species we analyzed on slide #7 of our June presentation was 60.

[2] Yes, the Green River drainage includes a sliver of north central Tennessee.  The faunal similarity between Kentucky and Tennessee has been one of the biggest surprises of the FWGO survey.

[3] A tip of the hat to our good friend Kevin Cummings for his gracious hosting at the Illinois Natural History Survey.