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!


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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.
406.580.7816
davidr@montana.edu

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
KATHERINE BOUMA
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.

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:
http://idahoes.fws.gov/
(See "Service to review status of four springsnail species."

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).

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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.

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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.

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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.

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."

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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.

Gigantic Pulmonates

Editor's Note #1.  This essay was published as: Dillon, R.T., Jr. (2019b)  Gigantic pulmonates.  Pp 113-120 in The Freshwater Gastropods of North America Volume 2, Essays on the Pulmonates.  FWGNA Press, Charleston.

Editor's Note #2. I subsequently re-identified the planorbid population inhabiting this "fancy landscape pond" as Helisoma scalare duryi.  See my posts of [5Jan21] and [7Feb23].

The fancy landscape at the office park near my home in Charleston features a narrow pond, perhaps three meters deep and over 100 meters long, with concrete lining and a natural earth base. It is inhabited by our three local pulmonate weeds (Physa acuta, Helisoma trivolvis, and Lymnaea columella) as well as by mosquito fish, tadpoles, and a variety of macrophytes both submerged and emergent. This pond has long served as the water source for my laboratory cultures of pulmonates, and as such I have visited it approximately every two weeks for 6 - 8 years.

About a month ago the pond was drained for cleaning. A crew subsequently spent quite a few days shoveling leaves, mud, vegetation and organic debris from the basin, leaving a few shallow pools scattered on a clean mud bottom. The photo at left above shows the drying pond at its lowest end, with the concrete standpipe that ordinarily regulates water depth in the background. A high-resolution close up of one of the drying pools with Helisoma trivolvis (both the living and the dead) much in evidence, can be downloaded [here]. As the figure below illustrates, the individual Helisoma were exceptionally large.

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A similar phenomenon also seems to occur occasionally in the Physa acuta population inhabiting the main pond at Charles Towne Landing State Park. I have many years of casual observations on this population, which has served as my source of control snails for experiments on the reproductive biology of Physa since 1988. In culture, P. acuta from this population reach maturity at about 6 mm shell length (seven weeks post hatch), and have never grown larger than about 12 mm when reaching the end of their life at 12 - 13 months of age (Wethington & Dillon 1993, 1997). For years I never saw an individual larger than about 12 mm in the wild. But on a casual visit in March, 2001, I discovered that the population was comprised almost entirely of gigantic individuals, 15 - 20 mm in shell length (below).


What might cause such sporadic cases of gigantism? Growth is indeterminate in all the basomatophoran pulmonates of which I am aware. But since growth rate slows dramatically at onset of reproduction, maximum size effectively becomes a function of size at maturity. Following Charnov and similarly minded evolutionary biologists from the 1980s and 1990s, I have suggested that size at maturation in pulmonates may be a function of survivorship schedule (Dillon 2000: 140 - 149).

In both my local Helisoma population and my local Physa population, gigantism appeared in the fall or winter and was not associated with parasitism. Both populations seemed stressed by low water, and probably severe temperatures. But neither population appeared to be starving, at least in the long term. And perhaps most strikingly, in neither population were eggs or juveniles in evidence. It is my hypothesis that gigantism in pulmonates may be prompted by some environmental perturbation postponing, perhaps even canceling, reproductive maturity.

Such a perturbation, although perhaps ongoing as gigantic individuals are observed, must have begun earlier in the season, when maturation would in an ordinary year have taken place. Its effect would be to improve survivorship above expected levels, perhaps through an unusual reduction in predation, parasitism, or disease. Did something kill the predators that ordinarily live in the ponds with my gigantic pulmonate populations without adversely affecting the snails themselves, triggering a growth spurt?

And do systematic malacologists have a history of being fooled by gigantism? About 300 km up the coast from where I write this essay is the home of Helisoma ("Planorbella") magnifica, a pulmonate of truly gigantic proportions (Figure below from plate 96 of Baker). Long feared extinct, a couple scattered populations of H. magnifica were re-discovered in 1988 near Wilmington, North Carolina, by Bill Adams and Andy Gerberich. The subsequent history of this species, tragic and comic by turns, is a tale best left for another day, and another teller. I know that a sample of H. magnifica was held in culture for a number of years, and that at least occasionally, magnifica adults bore offspring subsequently identified as H. trivolvis, with which magnifica co-occurs. The morphology of H. magnifica does not suggest simple gigantism of H. trivolvis, however, the magnifica shell being much more boxy and broad than the trivolvis shells shown above. The extent to which the shape of the pulmonate shell may be influenced by environmental cues is another topic upon which we might chew in the future.

For what its worth, our colleague Art Bogan and his colleagues (2002) reported mtDNA sequence divergence in the 4 - 9% range between a sample of four H. magnifica and sample of 9 H. trivolvis collected in Union County, a couple hundred kilometers west of Wilmington. Given Art's observation that sequence divergence within conspecific Helisoma populations ranged over 3%, however, a comparison of magnifica to a trivolvis population with which it co-occurs would have been much more cogent. But regardless of the status and fate of H. magnifica, the existence of great phenotypic plasticity in shell morphology should remain foremost in the minds of all of us struggling with the taxonomy and classification of freshwater pulmonates.

References

• Adams, W.F. & A. G. Gerbeich (1988) Rediscovery of Planorbella magnifica in southeastern North Carolina. Nautilus 102: 125-126.
• Baker. F. C. (1945) The Molluscan Family Planorbidae. University of Illinois Press, Urbana.
• Bogan, A.E., M. Raley, & J. Levine (2002) Conservation status of the magnificent ramshorn, Planorbella magnifica (Pilsbry, 1903), endemic to the lower Cape Fear River Basin, North Carolina. Abstract, American Malacological Society, Charleston.
• Dillon, R. T., Jr. (2000) The Ecology of Freshwater Molluscs. Cambridge University Press.
• Wethington, A. R. & R. T. Dillon (1993) Reproductive development in the hermaphroditic freshwater snail, Physa, monitored with complementing albino lines. Proc. R. Soc. Lond. B 252: 109 - 114. [pdf]
• Wethington, A. R. & R. T. Dillon (1997) Selfing, outcrossing, and mixed mating in the freshwater snail Physa heterostropha: lifetime fitness and inbreeding depression. Invert. Biol. 116: 192-199. [pdf]

Proceedings of the Charleston Symposium

As you may recall, the 2002 meeting of the American Malacological Society here in Charleston featured a symposium entitled, "The Biology and Conservation of Freshwater Gastropods." Our colleague Amy Wethington organized a related special session at that same meeting, "Pulmonates in the Laboratory."

Now (at long last!) I'm pleased to report that 12 papers from those two sessions have reached publication in the American Malacological Bulletin, Volume 19: 31 - 144. A table of contents is provided below.Single issues of the AMB are available from the office of the Editor-in-Chief: Dr. Janice Voltzow, Department of Biology, University of Scranton, Scranton, PA 18510-4625. The cost: $40 for members, $48 for non-members. Email Janice for more details: voltzowj2@Scranton.edu


Thanks to all of you on this list who were involved in bringing this symposium to successful fruition.


----------- AMB 19:31-144 (14Oct04) ---------------

• Dillon, R. T., Jr. The biology and conservation of freshwater gastropods: Introduction to the symposium.
• Richards, David C. & Dianne C. Shinn Intraspecific competition and development of size structure in the invasive snail, Potamopyrgus antipodarum.
• Mower, Christina B. & Andrew M. Turner Behavior, morphology, and the coexistence of two pulmonate snails with molluscivorous fish: A comparative approach.
• McCarthy, Thomas M. Effects of pair-type and isolation time on mating interactions of a freshwater snail, Physa gyrina (Say, 1821).
• Brown, Kenneth M., and Paul D. Johnson Comparative conservation ecology of pleurocerid and pulmonate gastropods of the United States.
• Dillon, Robert T., Jr., Charles E. Earnhardt, and Thomas P. Smith Reproductive isolation between Physa acuta and Physa gyrina in joint culture.
• Dillon, Robert T., Jr., & Robert C. Frankis High levels of mitochondrial DNA sequence divergence in isolated populations of the freshwater snail, Goniobasis.
• Stewart, Timothy W. & Robert T. Dillon, Jr. Species composition and geographic distribution of Virginia's freshwater gastropod fauna: A review using historical records.
• Britton, David K., & Robert F. McMahon Environmentally and genetically induced shell shape variation in the freshwater pond snail Physa (Physella) virgata.
• McMahon, Robert F. A 15-year study of intrapopulation, interannual shell-shape variation in a freshwater, pulmonate limpet population (Pulmonata: Basommatophora: Ancylidae).
• Glaubrecht, Matthias Leopold von Buch's legacy: Treating species as dynamic natural entities, or Why geography matters.
• Wethington, Amy R. & Robert Guralnick Are populations of physids from different hot springs distinctive lineages?

And forthcoming in the next AMB:

• Jokinen, Eileen H. Pond mollusks of Indiana Dunes National Lakeshore: Then and now.