Dr. Rob Dillon, Coordinator

Friday, December 23, 2005

Idaho Springsnail Panel Report

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019d) Report from the Idaho Springsnail Science Panel.  pp 141 - 147 in The Freshwater Gastropods of North America Volume 4, Essays on Ecology and Biogeography.  FWGNA Press, Charleston.

As most of you are aware, 2005 has seen a great deal of attention focused on the conservation status of the west American hydrobiid, Pyrgulopsis idahoensis. Although the “Idaho Springsnail” was placed on the federal endangered species list in 1992, a recent taxonomic reappraisal by Hershler & Liu (Veliger 47: 66-81) prompted the state of Idaho and Idaho Power to petition the US Fish & Wildlife Service (FWS), for delisting earlier this year. Several non-governmental conservation groups have lodged a competing petition, and the battle lines are now drawn. See my essay of April, 2005 on the “Idaho Springsnail Showdown” for a brief review.

On October 18 & 19 the FWS convened a “Springsnails Science Panel” at the Statehouse Inn in downtown Boise, Idaho for the purpose of making recommendations regarding the conservation status of the Idaho Springsnail. The panelists were Joe Bidwell (Oklahoma State University), Greg Clark (USGS), Stephanie Clark (University of Alabama), Billie Kerens (Montana State University), Leslie Riley (Washington State University), and myself. It occurs to me that the members of the FWGNA group might be interested in a brief report of these proceedings, with a complimentary side-salad on the relationship between science and public policy.

The basis for our two day discussion was an 82-page document from the FWS entitled “Best Available Biological Information for Four Petitioned Springsnails in Idaho, Oregon, Washington, and Wyoming.” We were also given 34 pages of peer review comments on this document, offered (doubtless) by many of you. My main impression was simple amazement that such a tremendous amount of information might be available on any single species of North American freshwater snail. My main recommendation (upon initial review) was simply that the title of the document be changed to better reflect its content, “Absolutely Every Scrap of Data that has Ever Been Collected, and Every Word that has Ever Been Written, about the Idaho Springsnail, Regardless of Quality.”

The most contentious issue was taken off the table before the October meeting even began. On page 9 of the “Best Available” document, the FWS reported its determination that the Idaho Springsnail is not endemic to the Snake River, as previously believed, but also inhabits Washington, Oregon, and Wyoming, as concluded by Hershler & Liu.

The most surprising tidbits of information in the report were, to me, the data on the population size of P. idahoensis in the Snake River. Studies by the Idaho Power Company have found an average snail density of 130 snails / m2 over 80 linear miles. This average includes the 32% of the sites where no snails were present, presumably uninhabitable. I think that the snake river Pyrgulopsis may constitute the largest single population of freshwater snails ever documented. Can anybody on this list think of a larger one?

The panel meeting itself was moderated by Mr. Phil Carroll, a professional facilitator, who favors the “modified Delphi method” of problem-solving. This approach carries a group of experts through a series of discussions and polls to a final vote where each participant invests some standard number of figurative chits to indicate his certainty regarding possible answers to the central question.

I found the entire two-day process intellectually nauseating. On the one hand, most of the questions we entertained were not scientific, nor framed in a way that could be answered by science. And in fact it was clear to me that the entire process was designed and controlled by well-meaning and hard-working people who nevertheless have no clue even what science is.

For example, we panelists spent most of the first afternoon discussing “How intrinsic factors (or extrinsic factors) contribute to population resiliency and vulnerability.” The units in which “population resiliency and vulnerability” might be measured never seemed to be at issue.

Some of our colleagues wrung their hands, saying “If we only had more information, these decisions would be so much easier!” Nonsense. We have more information on the Idaho Springsnail than any other freshwater gastropod in the world, except the medically-important species of the tropics. The questions we were asked in Boise were simply not answerable.

But on the other hand, I understand why the FWS would very much like to have information on “population resiliency and vulnerability” if such statistics could be calculated, to make the decisions it must make on endangered species. And I honestly can’t think of a better method to obtain such information other than asking for gut-level guesses from as large a sample of knowledgeable people as possible. So when I placed myself in the intellectual mindframe of a natural resources manager, or some similar public servant (as opposed to a scientist), the process ongoing at the Statehouse Inn was not uncomfortable.

For me the two-day meeting was like an intellectual roller coaster, periods of relative calm being followed by vertiginous drops, during which I desperately tried not to vomit.

But unlike the typical roller coaster, alas, the ride got worse as it proceeded. In the early afternoon of the second day we took a series of votes designed “to express [our] belief about what is the most likely timeframe for extinction and what is [our] confidence level in this specified timeframe.” We were each given a ballot with boxes labeled 1- 20 years, 21 – 40 years, 41- 60 years, 61- 80 years, and 100+ years, and asked to cast 100 chits into these boxes according to our judgments of when P. idahoensis might go extinct. These ballots were collected, tallied, discussed, and second and third rounds of voting ensued.

I was genuinely surprised by the time frames nominated, which seemed designed to bias our judgments quite low. I would have voted for “a million, billion, zillion years” or perhaps, “a ton of years” had those options been available.

Much to my dismay, this particular series of votes did not constitute the end of the matter. After tabulating the last round of ballots, our facilitator calmly informed us that the specific language of the endangered species act refers not to the simple extinction of a species, but to extinction “in a significant portion of its range.” Further, the date of that extinction has no absolute boundary, but is specified only as “the foreseeable future.” So we six scientists had been packed into a tiny windowless room in downtown Boise, Idaho, for two days and the entire discussion finally boiled down to “what fraction of a range is significant, and what length of time into the future is foreseeable.” At least we could agree on units of measurement.

And it could have been worse. Also present in the room, occasionally asking questions and making comments, was a second “Manager’s Panel” comprised of six middle-level FWS field supervisors, division heads, and so forth. We six scientists were allowed to leave on the afternoon of the 19th, but those poor souls were condemned to two additional days of discussion and voting.

I have no idea what recommendation emanated of the Boise meeting. I will observe that among all six of us on the science panel, nobody placed his modal expected extinction date to the left of the foreseeable future. From Boise, however, the decision-making process proceeds through the regional and national Fish & Wildlife Service offices, ultimately to appear in the Federal Register as a ruling by the Secretary of the Interior. Until then, the process is cloaked in secrecy.

For myself, I emerged from the meeting with a renewed conviction that science and politics don’t mix. Steven Jay Gould coined the term, “nonoverlapping majesteria” to describe the relationship between science and religion, but I think the description is just as apt for science and public policy. We have different languages, values, and worldviews. It is quite clear to me that science was horribly corrupted in at The Statehouse Inn in downtown Boise October 18 & 19, invoked to answer questions it could not answer, and to justify decisions it could not justify.

I imagine that most of you reading this essay will disagree with me. In fact, I myself wish I were wrong. Your comments and replies are always welcome!

And we’ll keep in touch,

Historical Note:

The Idaho Springsnail was removed from the US Endangered Species List in August, 2007
[Press Release]

Thursday, November 17, 2005

Aerial Dispersal of Freshwater Gastropods

To the FWGNA group,

I am once again indebted to Dr. Julian Harrison for calling my attention to a previously unconfirmed element of the South Carolina gastropod fauna, the little planorbid Promenetus exacuous. This brings the list of South Carolina freshwater gastropods up to 28 taxa.

Julian has collected Promenetus from lentic environments in two areas of the South Carolina coastal plain, one near Drayton Hall Plantation on the current outskirts of Charleston, the other by the Edisto River about 90 km inland. But the meat of the species’ range is much further north - generally above the glacial maximum. Promenetus does occur in coastal regions of North Carolina, increasingly scattered as one proceeds south. See the map below.
Julian Harrison also gets the credit for discovery of the limpet Hebetancylus excentricus in South Carolina. The distribution of Hebetancylus here is similar to that of Promenetus - it occurs in a few scattered coastal plain ponds. But Hebetancylus is a more southern species, the meat of its North American range extending from Florida to Texas. See map below.
The common factor in the occurrence of both Promenetus and Hebetancylus in South Carolina, other than that both were called to my attention by Julian Harrison, is that both occur in habitats frequented by migratory waterfowl. Charleston and the Carolina lowcountry lie directly beneath the Atlantic flyway, visited twice annually by millions of ducks, geese, and other migratory water birds. (An interesting radiotelemetric study has been published by the Atlantic Flyway Pintail Project.) All the ponds from which Promenetus and Hebetancylus have been collected here are certainly visited. In fact, the pond from which Hebetancylus was first reported is an ornithological research site. Both gastropods are small and clingy. Although the evidence is circumstantial, I think that Promenetus and Hebetancylus may owe their existence in South Carolina to dispersal through the air.

Broadening our discussion a bit, the distributions of Planorbula armigera and Valvata bicarinata in North Carolina look very similar to that of Promenetus in South Carolina - scattered coastal habitats associated with waterfowl. It is tempting also to attribute the single South Carolina population of Biomphalaria to aerial dispersal, although the import of aquatic vegetation may be a more likely explanation here.

To those interested in learning more about the aerial dispersal of mollusca, I would recommend the charming (1965) paper of W. J. Rees. Rees collected several anecdotes connecting freshwater gastropods to both birds and insects. The experiments of Malone (1965 a,b) and Boag (1986) are also interesting in this regard. References below.

In summary, one often sees the adjective “accidental” used in bird books to describe the occurrence of particular avian species outside their normal ranges. I would suggest that “accidental” might just as aptly be applied to certain occurrences of freshwater gastropods as well.

  • Boag, D. A. (1986) Dispersal in pond snails: potential role of waterfowl. Can. J. Zool. 64: 904 - 909.
  • Malone, C. R. (1965a) Dispersal of aquatic gastropods via the intestinal tract of water birds. Nautilus 78: 135-139.
  • Malone, C. R. (1965b) Killdeer (Charadrius vociferus L) as a means of dispersal for aquatic gastropods. Ecology 46: 551 - 552.
  • Rees, W. J. (1965) The aerial dispersal of Mollusca. Proc. Malacol. Soc. Lond. 36: 269 - 282.

Thursday, October 6, 2005

Bellamya (Cipangopaludina) News

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019d)  Bellamya ranching in North Carolina. Pp 7 - 9 in The Freshwater Gastropods of North America Volume 4, essays on Ecology and Biogeography.  FWGNA Press, Charleston.

Many of you will be familiar with the large invasive viviparid gastropods Bellamya (or Cipangopaludina) chinensis and B. japonica. Here in the U.S. one commonly sees Bellamya sold as a specialty item for the purposes of cleaning or clarifying the water in ornamental lilly ponds. The snail has been widely introduced into the wild - our colleague Jay Cordeiro has been monitoring their spread for several years. But the appearance of Bellamya is not generally greeted with the same alarm that accompanies the discovery of large ampullariid snails such as we discussed in August and September just past, primarily because Bellamya does not apparently eat living macrophytes. From a human standpoint, its introduction seems largely benign.

Below are three little news items involving American populations of Bellamya, the first personally collected, the second and third passed along from Jay Cordeiro and Rick Fox, respectively. All fall under the general heading of, "If the good Lord gives you lemons, make lemonade." Enjoy!

Bellamya Ranching in North Carolina
While on a field trip last month I was not surprised to discover large and apparently healthy populations of B. japonica in High Rock Lake and Tuckertown Reservoir, both impoundments of the Yadkin/Pee Dee River system in central NC. There were previous records from Lake Hickory of the Catawba River system next door, as well as several ponds and smaller populations scattered around the state. I would characterize High Rock and Tuckertown as "highly disturbed" environments, built in the 1920s by Alcoa for hydroelectric purposes and currently supporting a lot of recreational use, although such venues do not appeal to me personally (Photo below).

In any case, I had just finished making collections on High Rock at a very popular boat ramp east of Salisbury when I was approached by two state game wardens. They had lots of questions, and once we got beyond the usual "Who the heck are you and what the heck are you doing here?" our conversation turned to "these large snails." They related an interesting story.

Apparently one night in the not too distant past, their suspicions were aroused by a large band of fishermen seining or netting on the lake under cover of darkness. They and other officers swooped down on the nocturnal fisherman only to discover all their nets and coolers filled with "these large snails." The fishermen were Laotian, of Hmong descent. Since North Carolina does not apparently have any laws regulating the harvest of snails, the Laotian fishermen were allowed to continue.

I personally speculate that the Laotians may have previously "seeded" Bellamya into High Rock and Tuckertown Reservoirs. This may represent a previously unrecognized mechanism for the spread of Bellamya in the US. Of course, very few of us approve (in principle) of artificially spreading exotic organisms. But "snail ranching" to feed (perhaps impoverished?) people from what is otherwise an underutilized and already disturbed environment doesn't seem like much of a sin. If the good Lord gives you lemons...

Bellamya Roundup in Massachusetts
Our good friend Jay Cordeiro is calling for volunteers to hand-collect Bellamya from Johnson's Pond in Groveland, Massachusetts next Saturday, October 15. His (very cute!) PDF flier is available for download from the FWGNA web site [here]. Any of you in that part of the world are encouraged to contact Ms. Susan Park before October 10 for more details.

Jay is considering a mark-recapture study aimed at estimating the current size of the Bellamya population in Johnson's Pond, to be repeated over the next several years, in an effort to measure the effect of his roundup project. If he also launches a second mark-recapture survey in a nearby pond left undisturbed, he should be able to gather data on the regulation of population size in aquatic invertebrates of general importance. Looks interesting!

Jay tells me he plans to "euthanize" his Bellamya harvest. Any Laotian folks up in your part of the world, Jay? How about "boil?"

Bellamya as a Model for Invertebrate Anatomy
My thanks (and a tip of the hat!) go to Rick Fox of Lander University up in Greenwood, South Carolina. Rick has developed a truly impressive investigation for his Invertebrate Zoology laboratory featuring the dissection of Bellamya, and made his detailed notes and instructions available through Invertebrate Anatomy Online. The site is best viewed with MS Explorer - some of his 19 cleanly-drafted figures don't display with Netscape.

Saturday, September 17, 2005

Pomacea in Georgia

Expanding on the theme of my post last month, this morning's newspaper carried an Associated Press article with the following headline: "Snails Threaten Georgia Wetlands." Georgia DNR is reporting the discovery of a reproducing population of invasive Pomacea in ponds and streams of the Alabaha River system, a tributary of the Satilla in SE Georgia. Although not actually in the drainage of the Okefenokee Swamp, officials are concerned that the snail might be spread 20 miles south to the Swamp and cause significant environmental damage. A press release from the Georgia DNR-Wildlife Resources Division (upon which the AP article was based) is appended below.

The article refers to Pomacea as the "channeled apple snail," which is a good, descriptive common name. Elsewhere in the world the critter is more commonly called the "golden apple snail," because (at least initially) many of the populations were albinistic. The snail has become a terrible pest in Hawaii and throughout east Asia where rice and taro are grown. Breeding populations have also become established in Florida, Texas, and California. I've appended a few web references below the Georgia DNR article if you'd like to learn more.

Meanwhile, we here in Charleston are once again manning the southern breastworks. First Sherman and now this. Perhaps we'll have a bit more time to prepare for this invasion than the last.

Ga Wildlife Resources Division News Story
BLACKSHEAR, Ga. (9/13/2005)
Invasive South American Snails Breeding in South Georgia

It’s just the kind of tourism Georgia doesn't need. Recent surveys conducted by the Georgia Department of Natural Resources, Wildlife Resources Division (WRD) have documented breeding populations of a large, invasive species of snail native to South America. During a recent search, WRD biologists removed 79 of the channeled apple snails and 151 egg masses from a pond in Pierce County in a span of less than four hours.

A live snail found near the Alabaha River in Pierce County in early 2005 was identified as a channeled apple snail. The specimen was the first of its kind discovered in the state. Since then, live apple snails and eggs have been found in several ponds and streams in the Alabaha River system, a tributary of the Satilla River in Southeast Georgia.

"These snails have a voracious appetite for aquatic plants, which many native species depend on for foraging and shelter," said WRD Wildlife Biologist Brett Albanese. Shells of channeled apple snails can reach a width of more than two inches and a height of three inches, and are yellowish to brown in color. Channeled apple snails have established populations in at least six Florida counties, and breeding populations of the species also exist in Texas, California and Hawaii.

Initial findings of the snails in Georgia raised speculation that the specimens might have been aquarium pets released into the wild, but the subsequent discovery of a large population in a popular fishing spot may indicate otherwise. "We now suspect that these snails may have hitched a ride into Georgia on a fishing boat that had been in Florida waters, where the apple snail has also been introduced," said WRD Fisheries Technician Chad Sexton.

The discoveries were of particular interest to biologists because of the invasive nature of the species. An array of problems can arise when pet owners or fishermen introduce non-native species into Georgia’s waters. Non-native or nuisance species can be spread when anglers release live bait into the water or move between water bodies without cleaning boats and trailers.

The WRD Fisheries Management Section and the WRD Nongame Wildlife and Natural Heritage Section have been working to monitor the spread of apple snails in the Alabaha River system. They are experimenting with trapping and manually harvesting adult snails from ponds and streams and manually removing the egg masses from trees. "Although the track record for eradicating non-native species is not promising, biologists hope that they can halt or slow the spread of these snails in South Georgia," Albanese said. "One reason for optimism is that we can target two life stages of the snails ­ both the eggs and the adults ­ for removal."

Conservation agencies nationwide are working to stop the spread of non-native aquatic plants and animals, citing concerns about the potentially harmful impact to native species. "The wrong organism in the wrong place can eat or out-compete native species, which can have serious impacts on an entire aquatic community. Invaders can also spread non-native diseases," Sexton said.

For more information about aquatic nuisance species, visit http://www.protectyourwaters.net/ or http://www.gofishgeorgia.com/. Additional information on identifying apple snails is available at http://www.applesnail.net/. Georgia residents who think they have found an apple snail should collect it, photograph it and provide detailed locality information to WRD Fisheries Management in Waycross at (912) 285-6094, or WRD Headquarters at (770) 918-6400. Citizens should also be on the lookout for the apple snail’s bright pink eggs, which are laid on trees and shrubs above the waterline.

On-line Pomacea References:

Addendum, 21Sept05

To the FWGNA group:

Our thanks are due to Bob Howells for the update on Texas Pomacea copied below. Bob has also sent me three nicely-produced fliers on the subject, which are now available for download from the FWGNA site.

Bob is most smitten by recent DNA evidence suggesting that his Texas Pomacea are not true P. canaliculata, as have been introduced throughout the Pacific, but rather something else. Given the ease with which these animals can be cultured, however, I think it would be a shame to jump to such a conclusion without controlled breeding experiments. I understand that TX/HI Pomacea crosses are next on Ken Hayes' to-do list. Right, Ken?

Keep in touch!

Subject: RE: Pomacea in Georgia
Date: Mon, 19 Sep 2005 08:32:37 -0500
From: "Robert Howells" Robert.Howells@tpwd.state.tx.us
To: "Rob Dillon" dillonr@cofc.edu

Thanks for the heads up on the most recent applesnail information. There are a few points of interest. (1) We (TPWD/USDA/etc.) heard about the first Pomacea collections in Georgia last Spring…literally during a USDA applesnail meeting being held at that time in Houston. However, additional specimens have turned up in Georgia more recently. (2) Rob Cowie and his associates have determined that the large channeled Pomacea we have in the U.S. (those tested so far…) are not true P. canaliculata like those in Hawaii and in the Philippines. (3) The ANSD article was rewritten extensively by the editor and without my knowledge or approval. It contains some completely false information. Never cite it!!!! (4) I have gotten together with Alex Karatayev and Lyubov Burlakova (SFASU) and Romi Burks and one of her students (SWU) and drafted a chapter for a book by Ravi Joshi on Ampullariidae. We have addressed all the species of Ampullariidae in North America (there was actually a Canadian introduction a while back). Joshi expected the book out sometime this fall. Our chapter has a lot of photographs and range maps as well as a lot of new information on Texas populations being generated by the academic folks in Texas. (5) Attached are some handouts related to Pomacea in Texas that update status and terminology.

Bob H.

Howells, R. G. (2005) Exotic Applesnails in Texas Waters [PDF]
Howells, R. G. (2005) Invasive Applesnails in Texas: Status of these harmful snails through spring 2005 [PDF]
Howells, R. G. (2005) Channeled Applesnails: Recommendations to Prevent Their Spread [PDF]

Thursday, August 11, 2005

Ampullariids Star at Asilomar

I am pleased to report that the annual meeting of the American Malacological Society, held in late June at the Asilomar Conference Center near Monterey, CA, was a great success. The registered attendance of about 150 well-assorted malacologists combined to present 120 papers and posters, including 10 on freshwater snails, as appended to the end of this message. Abstracts are available from the AMS web site:

The quality of the papers was generally excellent. And on Monday morning June 27, Yoichi Yusa of Nara Women’s University (yusa@cc.nara-wu.ac.jp) may have presented the most important research results I have ever heard in my 29 years of scientific meetings.

Although most mollusks are gonochoristic (sexes separate), great mystery has long surrounded molluscan mechanisms of sex determination. There have been a couple scattered reports of sex chromosomes in prosobranch gastropods. The research of Stan Allen, Ximing Guo and their colleagues in the 1990s suggested that sex determination in (partially protandric) oysters seems to be controlled by a single locus with a dominant male allele. But population sex ratios are often way off 1:1 in the Mollusca, and sometimes the bias may be attributable to differential growth or survivorship in the sexes, or partial protrandry, and sometimes it clearly isn’t.

At Asilomar Yusa described an impressive series of breeding experiments strongly suggesting that gender in Pomacea canaliculata is controlled by a small number of additive sex-determining genes, apparently scattered through the genome, inherited from both parents. Such an oligogenic sex determining mechanism has never before been suggested for the Mollusca. It seems clear to me that sex ratios might easily vary from 1:1 in this situation, especially in populations subject to drift and bottlenecks, such as many freshwater prosobranch snails. The evolutionary implications are profound.

While we’re on the subject of the Ampullariidae, I should also report that Ken Hayes (working with Rob Cowie at the University of Hawaii – Manoa, khayes@hawaii.edu) has been sequencing the daylights out of the family. He has (to this point) sampled somewhere around 9 – 13 Pomacea species from the Americas, as well as representatives of the genera Marisa, Asolene, Lanistes and Pila. His database currently includes about 435 individual CO1 sequences, from 40 populations in their native ranges and 80 introduced populations.

The big headline (from my outside perspective) is that Ken seems to find that sequence methods are useful in discriminating Pomacea species. Freshwater and terrestrial gastropods both typically show great intrapopulation sequence variation, to the point that the distinction between populations known to constitute valid biological species may be swamped. But Ken reports that the mean maximum intraspecific sequence divergence in his Pomacea data set is around 5%, while mean minimum interspecific divergence is around 10%, suggesting that sequence data may prove to be a useful tool for specific diagnosis in the Ampullariidae.

Although the various Pomacea species are not terribly difficult to culture, I don’t believe that Ken has breeding data of sufficient quality to absolutely confirm the biological status of his nominal species groups. Thus his sequence data, strictly speaking, remain uncalibrated. But he reassures me that anatomical morphology supports the specific distinctions being made by his CO1 sequences in all cases where they’ve looked. Regardless, it’s nice to see sequence data find some application not dependent on the tenuous assumptions of phylogenetic reconstruction.


Freshwater gastropod presentations at AMS 2005, Asilomar:
  • Robert T. Dillon, Jr., John D. Robinson, and Amy R. Wethington. Empirical Estimates of Reproductive Isolation Among the Freshwater Pulmonate Snails Physa acuta, P. pomilia, and P. hendersoni.
  • Kenneth A. Hayes. Preliminary phylogenetic assessment of invasive apple snails in Asia and beyond.
  • Cynthia G. Norton and Jennifer M. Bronson. The relationship between body size, growth, and egg production in the hermaphroditic freshwater snail, Helisoma trivolvis.
  • Robert S. Prezant and Eric J. Chapman. Temporal Community Structure and Biodiversity of Malacofauna from an Urban New Jersey Pond.
  • David C. Richards, C. Michael Falter, Gary T. Lester, Ralph Myers. Mollusk Survey and Basic Ecological Studies in Hells Canyon, Snake River, USA.
  • Ellen E. Strong. New morphological data for Pleuroceridae (Gastropoda, Cerithioidea): implications for monophyly and affinity of the family.
  • Andries Ter Maat, Cora Montagne-Wajer and Joris M. Koene. The year of the pond snail.
  • Lori Tolley-Jordan. Impacts if urbanization on the biodiversity of the imperiled snail fauna (Gastropoda: Prosobranchia: Pleuroceridae) of the Cahaba River, Alabama, USA.
  • A.R. Wethington, M.K. Smith, G. Oliveira, F. Lewis, and D.J. Minchella. Genetic Structure of Biomphalaria glabrata populations sampled from a schistosomiasis endemic region.
  • Yoichi Yusa. Genetics of Sex Ratio Variation in the Apple Snail, Pomacea canaliculata.

Thursday, June 23, 2005

New Zealand Mudsnail Conference

The introduction of the "New Zealand mud snail" (Potamopyrgus antipodarium) into steams of the American West has been attended by a blossoming of interest in what was already perhaps the best-known freshwater prosobranch. Our colleagues in Montana deserve special commendation for their remarkable research efforts in this regard.

Below is an announcement for the 4th (yes, fourth!) NZMS Conference, scheduled for Bozeman in mid-August. There's still time to submit an abstract, but hurry! Contact Dave Richards directly for more details.

And follow some of those links from the conference web site given below if you want to be impressed at the state of our knowledge on Potamopyrgus!

From: "David Richards" davidr@montana.edu
To: "Rob Dillon" DillonR@cofc.edu
Subject: 4th NZMS Conference
Date: Tue, 3 May 2005 09:39:12 -0600

Just a reminder the 4th New Zealand Mudsnail Conference will be held August 16-18, 2005at Montana State University, Bozeman, MT. For more info go to: http://www.esg.montana.edu/aim/mollusca/nzms/con4.html

Call for papers ends June 30. So get your abstracts in by then!!

Hope to see you all there!
David Richards
Ph.D.Research Ecologist,
EcoAnalysts Inc.

Monday, May 9, 2005

Ivory-billed Freshwater Gastropods

Congratulations are in order for our colleagues Jeff Garner of the Alabama DCNR and Stephanie Clark of the University of Alabama! Last week The Nature Conservancy announced that both researchers have recently rediscovered freshwater gastropods previously feared extinct. An article from The Birmingham News is appended below.

Jeff collected Goniobasis vanuxemiana and G. lachryma diving in the Coosa River below the Logan Martin Dam east of Birmingham. Stephanie found Clappia cahabensis in the Cahaba River south of Birmingham, closer to Tuscaloosa. Their discoveries were unrelated but highly coincidental - both occurred last year and were reported independently at the annual Alabama Mollusk Meeting. TNC's decision to issue a combined press release last week was prompted by the big Ivory-billed Woodpecker buzz.

Good job to all involved!

------[The Birmingham News 3May05]-----------

Biologist, student find 3 snails thought to have been extinct
Coosa, Cahaba Rivers turn up prizes the discovery of snails believed to have been wiped out by human actions
Tuesday, May 03, 2005
Birmingham News staff writer

Three snails listed as extinct have been rediscovered in Alabama's rivers, the Nature Conservancy plans to announce today.

Jeff Garner, the Alabama Department of Conservation and Natural Resources' mollusk biologist, rediscovered the cobble elimia and the nodulose Coosa River snail on a stretch of the Coosa that remains free-flowing between Lake Logan Martin and Neely Henry Lake. And Stephanie Clark, a postdoctoral student from Australia, found a Cahaba pebblesnail in the Cahaba River in Bibb County.

Alabama is recognized as the globe's most densely populated home of mollusks - the snails and mussels that dot the beds of rivers, the acres of white shells that gave Muscle Shoals its name. The state also is known to be the nation's top spot for extinct and imperiled mollusks. Of 174 species of aquatic snails to occur here, 39 are presumed to be extinct.

The Coosa River is home to hundreds of aquatic animals, making it a global hot spot for snails and mussels. For that reason, it also has a more lethal distinction - the site of the largest extinction in the history of the United States.

From 1917 to 1967, dams were built along the length of the Coosa River until it became a series of reservoirs. Dozens of fish, mussels and snails that evolved to live and breed in the fast-flowing water on the shoals and riffles of the Coosa reefs lost their niche. Animals were drowned, cut off from each other or stuck in water so dirty that they could not reproduce, biologists say.

In recent years, scientists have discovered some species hiding in the "headwaters" of the dams, the streams between reservoirs where the Coosa still retains some of its original habitat. So Garner went diving below Lake Logan Martin and found two species that hadn't been spotted since the dams changed the river. Garner knew immediately what the small, brownish spirals were. "One of these I found is pretty distinctive," Garner said. "I've always said it was my favorite snail - I hated it was extinct. It sort of has teardrops around the periphery."

Clark, who began postdoctoral research at the University of Alabama last year, didn't know immediately what she was looking at. But she knew it was unusual. She was accompanying a graduate student to the Cahaba River National Wildlife Refuge in Bibb County when she began wandering around looking in the usual spots a biologist would look for river snails. "Behold, there was this oddball snail under a rock," Clark said. "I didn't know that I'd found an extinct one straightaway, but I knew I'd found something that I hadn't seen before."

The Cahaba pebblesnail, a round, yellow snail only about a quarter of an inch in length, hadn't been spotted since 1965. "That these things are being found is a surprise, but it's not shocking," said Paul Hartfield, an endangered species biologist for the U.S. Fish and Wildlife Service in Jackson, Miss. In the past 15 years, scientists have turned their attention to the snails of Alabama. The study of mollusks had dwindled to nearly nothing by the early 1970s, with students lured away to sexier, high-tech fields, he said. Then after the passage of two federal laws, the Endangered Species Act and the Clean Water Act, the field was in demand again, he said. It took until the 1990s for the science to mature and for great numbers of experts to begin looking for the snails that once covered Alabama's river bottoms.

In recent years, Garner has found several species believed to have been extinct, including a snail in the Locust Fork, a mussel in the Alabama River and a mussel in the Tennessee River. Clark last month collected two snails she believes have never been recorded. "The number of people who are capable of looking grows every day," Hartfield said. "This is a big basin when it was just me out there looking for snails and driving over from Mississippi for four or five days. Now what do we have? We have grad students from Australia."

However, some spots had been surveyed before but only recently have snail hunters had any luck, said Paul Freeman, a freshwater ecologist for the Nature Conservancy of Alabama, the land conservation group that secured the Cahaba refuge for preservation. He believes that may have something to do with cleaner water and better habitat brought by three decades or more of environmental laws. "Folks had been looking for these critters," Freeman said. "It's not just an artifact of people not looking."

Although he believes rapid growth in the river basins has negated many of the improvements, Hartfield said it may not be a coincidence that Alabama Power Co. has managed for good river habitat in the stretch where the two Coosa snails were found. He said their survival will depend on the continued goodwill of the company. He said he only wished more Americans realized the value of mussels and snails, which filter water, clean river bottoms and serve as food for birds, small mammals and aquatic animals. "Those snails and mussels have a lot to do with quality of life for the people of Alabama," he said.

E-mail: kbouma@bhamnews.com 1965.

Thursday, April 28, 2005

Idaho Springsnail Showdown

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2019d) Idaho Springsnail Showdown.  Pp 137 - 140 in The Freshwater Gastropods of North America Volume 4, Essays on Ecology and Biogeography.  FWGNA Press, Charleston.

Last Wednesday the US Fish & Wildlife Service (Boise Office) announced a 90-day comment period on a pair of competing petitions: one to remove Pyrgulopsis idahoensis (the "Idaho springsnail") from the federal endangered species list, the other to retain it and add several additional Pyrgulopsis populations from Wyoming and Oregon. The April 20, 2005 notice in the Federal Register is available as a PDF file from the link below. The purpose of this essay will be to briefly review the recent history of this simmering controversy from the standpoint of an interested outsider, with an eye toward patching a rift I fear may develop within the community more directly involved.

Pyrgulopsis idahoensis was one of five freshwater gastropods from the Snake River watershed added to the federal endangered species list in December, 1992. At that time, the species was believed to be restricted to an 35 mile stretch of the main Snake River below the C. J. Strike Reservoir. But as is too often the case, some fundamental background work on the biology of the animal had yet to be done. Early last year Hershler & Liu (2004a,b) reported that Pyrgulopsis populations conspecific with P. idahoensis inhabit three other regions: the upper Snake River drainage around Jackson Lake, Wyoming, springs scattered among Snake and Great Basin drainages in southeast Oregon, and the Columbia River on the Oregon/Washington border. The populations in the vicinity of Jackson Lake were previously identified as P. robusta while the SE Oregon populations were previously assigned to P. hendersoni. Since the nomen P. robusta (Walker 1908) has priority over idahoensis and hendersoni (both Pilsbry 1933), Hershler & Liu synonymized all these populations under P. robusta.

Last June the State of Idaho, together with the Idaho Power Company, petitioned the Fish & Wildlife Service to remove P. idahoensis from the federal endangered species list. This was followed in August by a petition from several (non-governmental) conservation groups to list the Pyrgulopsis populations from all four of the regions mentioned above. Both petitions referred to the data of Hershler & Liu (2004a), while reaching different conclusions from it. Last week the FWS responded by announcing a status review and a solicitation to the public for comments and information on both petitions.

I would encourage any of our colleagues with data relevant to this issue to communicate with the US Fish and Wildlife Service before June 20. Visit the Snake River FWS link below for further details.

I have a concern of a secondary nature, however, which I think should be addressed within our professional community, rather than through the federal agencies and the various interest groups involved in the pending Idaho springsnail showdown. I perceive some danger that we may begin to fight among ourselves on this issue. I want to point out that we are all on the same team here, and to the extent possible we need to be careful not to antagonize each other.

Bob Hershler and Hsiu-Ping Liu are excellent scientists, and their 2004a paper in The Veliger meets the highest standards of systematic malacology. Any professional who has seen their research findings will respond by referring to all the Pyrgulopsis populations involved in this matter as P. robusta. I am not asserting that this is The Truth, only that the conclusions of Hershler & Liu must become the lead hypothesis, against which any other hypothesis may be tested. Instead, the petition filed by the conservation groups in August continued to refer to these populations as separate species: the Idaho springsnail (P. idahoensis), the Jackson Lake springsnail (P. robusta), the Harney Lake springsnail (P. hendersoni) and the Columbia springsnail (P. spp. A), which has never been recognized as specifically distinct by any professional malacologist. The petition criticized and picked at the work of Hershler & Liu, suggesting that they "overlooked key differences between the four species." Nonsense.

Worse, I understand that Bob Hershler's motives may have been impugned. He and Hsiu-Ping did receive part of their funding from a law firm whose clients include Idaho Power, but to suggest that this affected their scientific judgment is an insult.

There seems to be a confusion widespread among environmental advocates to the effect that "splitting is good, lumping is bad." Taxonomists who split out new species at the drop of a nucleotide are seen as allies in the good fight, while those of us who understand interpopulation variation are painted as soldiers in the service of darkness. The root of this problem is the mixture of science and politics, but I'll resist getting on my high horse about that, for now.

Returning to the western Pyrgulopsis, however, the scientifically responsible (and collegial!) approach for the Conservation Groups would have been to petition for the listing of P. robusta, period. Any confusion regarding the relationship between the nomena "P. robusta" and "P. idahoensis" could have been cleared up in a couple paragraphs of introduction. It's probably not possible, nor possibly even desirable, for these groups to modify their August petition to the FWS at this point. But somebody owes our colleague Bob Hershler and apology. And better communication among all members of the team in the future, OK?

Links & References

Hershler, R. & H-P. Liu (2004a) Taxonomic reappraisal of species assigned to the North American freshwater gastropod subgenus Natricola (Rissooidea: Hydrobidae). The Veliger 47: 66-81.

Hershler, R. & H-P. Liu (2000b) A molecular phylogeny of aquatic gastropods provides a new perspective on biogeographic history of the Snake River region. Molec. Phyl. Evol. 32: 927-937.

US Fish & Wildlife Service. Notice of two 90-day petition findings...Federal Register 70: 20512-20514. [PDF]

U.S. Fish & Wildlife Service, Snake River Office:
(See "Service to review status of four springsnail species."

Friday, February 18, 2005

Shell morphology, current, and substrate

Editor's Note #1.  This essay was published as: Dillon, R.T., Jr. (2019b)  Shell morphology, current, and substrate.  Pp 121-126 in Freshwater Gastropods of North America Volume 2, Essays on the Pulmonates.  FWGNA Press, Charleston.
Editor's Note #2.  I subsequently re-identified the planorbid populations inhabiting Wakendaw Lakes as Helisoma scalare scalare on the riprap stones and Helisoma scalare duryi in the weedy ponds.  See my posts of [5Jan21] and [7Feb23]. 

In my post of November 2004 I examined the phenomenon of gigantism in pulmonates, taking as a point of departure the population of Helisoma trivolvis inhabiting an ornamental pond near my Charleston neighborhood. This month I'll develop that theme in an entirely different direction, focusing not on the mean shell diameter achieved by populations of Helisoma in the lowcountry, but on the spire height.

Across the Cooper River east of Charleston lies the suburb of Mt Pleasant, a bedroom community that has witnessed tremendous growth in the several generations since prosperity returned to the Carolina lowcountry. Among the scores of housing developments sprawling across this former patchwork of swampy forests is the subdivision of "Wakendaw Lakes." The photo above shows the low earthen dam constructed to retain the largest of the Wakendaw "Lakes." The nomen "pond" would be more descriptive of this shallow body of water, perhaps 1 - 2 hectares in extent, weedy and protected. It hosts the usual pulmonate fauna of the Charleston area, including a population of Helisoma trivolvis bearing shells that may tend to be a bit more narrow and compressed than we think of as typical (Below, right).

Excess water from the pond overflows a standpipe and exits through an open channel perhaps 2 meters wide at the base of the dam, then runs no more than 3 - 4 meters before disappearing into a culvert under the road. I gather that there must be substantial groundwater input to the pond, for the flow in the channel is mild but constant year round. Residents tell me that the current can be extreme in times of storm. The engineers who built this small work thoughtfully lined the entire four meters of channel with granite rip rap stones to forestall erosion.

Grazing on the stones in the moderate current one can find a population of Helisoma with the very peculiar shell morphology shown above left. The animals are often so obliquely coiled as to violate the definition of planispiral, effectively retaining the shell morphology normally associated with juveniles. But several years ago I ran a batch of allozyme gels comparing the populations above and below the dam, and was able to confirm that all the Wakendaw animals belong to a single randomly-breeding population of H. trivolvis.
Once again, I think the best explanation for this phenomenon lies in ecophenotypic plasticity. The planispiral shell borne by typical H. trivolvis in lentic waters enfolds an air bubble, which the snails use to regulate their buoyancy as they graze on floating or emergent vegetation. The narrow aperture of typical trivolvis may function as a defense against smaller predators (such as minnows) that might seek to snatch the snail's body from inside its shell. But a narrow, planispiral shell is worse than useless in a lotic environment. Thus individual H. trivolvis born on rocks in flowing water might retain a lower, broader shell to present less drag in the current, and a wide aperture enfolding a broad foot with which to cling. And again I emphasize, no genetic divergence need be involved.
As all of us in this group are aware, the taxonomy of freshwater gastropods both here and around the world rests largely, if not entirely, on shell morphology. In Florida, the related species Helisoma duryi and H. scalare are characterized by a broad, "buliniform" shell morphology very much like the H. trivolvis population of the rocky channel at Wakendaw. Burch reprinted a lovely 1934 figure of H.A. Pilsbry's suggesting evolutionary relationships among duryi, scalare, and several other species of Florida planorbids with low, more typical spire heights back to the Pliocene (above). I hate to be cynical, but I can think of an easier explanation.

Monday, January 24, 2005

Gillia Rediscovered

I am pleased to report the rediscovery of Gillia altilis in South Carolina, the 26th freshwater gastropod taxon confirmed living in the state today. This discovery, in addition to its value as an item of general good news, has strengthened a couple of convictions I've held for some time, perhaps of some broader interest, perhaps now worth sharing.

But first, a bit of biological background. Faithful correspondents may remember an essay I posted on 26May04 admitting my own long standing confusion regarding Gillia, Amnicola, Lyogyrus and Somatogyrus, four hydrobiid genera of the southern United States bearing similarly plain shells. That essay featured a photo comparing the four taxa that may be worth revisiting [Somatogyrus in the Southeast].

In any case, Gillia is much larger than any of these other hydrobiid genera, and is really quite unmistakable, now that I've held one in my hand. The Figure Below shows a 7.8 mm individual crawling in a beaker. The collection I made earlier this month was comprised entirely of adults ranging from 6 - 8 mm in shell length, twice the size of typical adults from either Amnicola or Somatogyrus, three times that of Lyogyrus. The shell is intermediate in thickness between the lightly-shelled Amnicola, more characteristic of lentic environments, and the heavily-shelled Somatogyrus, an inhabitant of rocky riffles.

Gillia altilis was first described by Lea (1841) using specimens sent him from the Santee Canal, an 1800 - 1850 passage between the port of Charleston and the Santee River 40 miles north. Only remnants of that canal remain today. The Charleston Museum holds two nineteenth-century lots of Gillia, one labeled simply "Santee Canal" and the other "Lynch's Creek."
I rediscovered the species Tuesday, January 11, at the US 52 bridge over the Lynches River 8 miles south of Florence, where I'd stopped on a whim. We'd had two weeks of unusually mild weather here in the southeastern US, and very little rainfall. The Lynches River was very low, and the morning so warm and bright, I pulled off the road primarily to stretch my legs and enjoy the fresh air. The water was black (as normal) but clearer than usual. I found Gillia altilis moderately common on the riprap used to stabilize the banks directly under the bridge. Individuals were also grazing on hard-packed clay. Three other freshwater gastropods were also present: Physa acuta, Goniobasis catenaria catenaria, and Amnicola limosa. Sometimes it seems to me that hydrobiid populations are positively associated - the occurrence of one species making a second more likely.

Here's the first moral I have derived from this experience - the value of revisiting sample sites. I had previously made collections at this site at least three or four times in the past under good conditions and had never found a trace of Gillia. Certainly, I had no previous observations from the winter, nor had I previously sampled water conditions quite this low. But I feel certain that Gillia is a perennial, and as common and conspicuous as the things were earlier this month, it's hard to believe I missed them entirely four times. I was tempted to subtitle this essay, "Humbled by hydrobiids again."

I've had similar experiences many times in the past. There's a spot on the Combahee River at Yemassee about 50 miles south of Charleston, for example, I've sampled at least annually for eight years. It's the type locality of Physa hendersoni, which we've been using for experiments on reproductive isolation in pulmonates. Prior to last March I had catalogued five pulmonate species from the site, generally collected during the course of my hunts for P. hendersoni. Last March, however, I found every stick and rock in the Combahee River covered with Amnicola granum, a species of which I had no prior record, and the five pulmonates had almost vanished. Freshwater gastropod populations are flashy. Revisit your sites.

The second moral of this story is never to underestimate the hidden potential of crappy rivers. The Lynches River arises in the lower piedmont of South Carolina, and on its roughly 150 mile journey to join the Pee Dee River passes through a watershed characterized by intensive row crop farming. Erosion and sedimentation have certainly been major problems for over 300 years, and who knows what sort of chemicals they spray on that cotton. Yet Goniobasis is very common in several of its upstream tributaries, and (again, as faithful readers may remember) the only modern record of Lioplax in South Carolina is also from the Lynches, about 40 miles upstream from the US 52 bridge (See my post of 26Aug04). To appreciate the biodiversity value of any river, one needs much more than a glance at a map and a few casual visits.

The web page I posted on 9Mar04 to report the results of my (510 record) survey of the Freshwater Gastropods of South Carolina is now badly out of date. In the section on "recommendations" I wrote:
"The status of Gillia altilis in South Carolina, its type locality, is worrisome. Burch & Tottenham (1980) quote the range given by Walker (1918): 'Atlantic drainage from New Jersey to South Carolina,' although populations apparently live as far north as Vermont and west to Lake Ontario (Jokinen 1992). I have seen fairly recent collections of Gillia from the Waccamaw River of southern North Carolina, but have to date been unable to confirm its modern occurrence here."
The modern occurrence of Gillia in South Carolina is now no longer in doubt. It is the continued existence of the species here that becomes the question. Gillia should shoot right to the top of our state list of aquatic species of concern.