> Recommendations: 
   North Carolina Atlantic drainages

The earliest review of potentially endangered freshwater gastropods inhabiting North Carolina was that of Fuller (1977). Meeting at the North Carolina State Museum, a committee headed by Fuller suggested threatened status for Helisoma magnifica and endangered status for both Lioplax subcarinata and the hydrobiid population(s) of Lake Waccamaw. Helisoma eucosmium was believed to be extinct at that time, and H. magnifica feared so. A second group of malacologists met at the NSCM in the late 1980s, this body headed by W. F. Adams (SCFTM 1990). They concurred regarding the extirpated status of H. eucosmium, suggested endangered status for H. magnifica, and added that the conservation status of Ferrissia hendersoni and two hydrobiids from the Lake Waccamaw area might be cause for special concern.

More recently, the (2005) North Carolina Wildlife Action Plan has listed ten freshwater gastropods "prioritized for conservation," seven of which are Atlantic species: the two planorbids, two hydrobiids, and Ferrissia species listed above, plus Somatogyrus virginicus and Viviparus intertextus. The NatureServe Explorer database [accessed 6/06] listed five G1 or G2 species from NC Atlantic drainages - H. magnifica, two Waccamaw hydrobiids, Somatogyrus virginicus and Micromenetus alabamensis.

The present survey suggests that most of the species listed above are not, in fact, threatened or endangered.  Basch (1963) synonymized Ferrissia hendersoni under F. fragilis, which we have recently synonymized under F. rivularis (Dillon & Herman 2009). Micromenetus alabamensis a synonym of Menetus dilatatus (Burch 1989), both species common and widespread throughout the state. Viviparus intertextus is indeed uncommon in North Carolina, but is much more abundant in South Carolina and elsewhere through its extensive range. Neither Lioplax subcarinata nor Somatogyrus virginicus is as rare as has previously been feared. We were especially surprised and pleased to chart 70 records of Somatogyrus in North Carolina, spanning five drainage systems and three ecoregions.

On the other hand, our survey suggests that the conservation status of the Waccamaw hydrobiids is a legitimate cause for concern. Floridobia sp. appears to be endemic to Lake Waccamaw and its direct tributary, Big Creek. The lake’s fauna also includes two endemic mussels and three endemic fishes, and is largely protected within a state park. The Floridobia population inhabiting it should be formally described. Previous suggestions that a second undescribed species of hydrobiid snail may inhabit Lake Waccamaw require further evaluation. The NCSM specimens we examined putatively representing this species were mixed lots, indistinguishable to our eyes from common Amnicola limosa and A. grana.

Both of the planorbid species endemic to North Carolina also merit further study and protection. Helisoma magnifica appears to be restricted to scattered lentic environments in the lower Cape Fear River system near Wilmington. The species has not been reported in the wild since that area was hit by several hurricanes in the late 1990s. We are not certain whether H. magnifica may yet survive under captive propagation, or whether it may be extinct.

We were pleased to find several individuals of Helisoma eucosmium in NCDWQ samples from the Wiccacon River in the northeastern part of the state. This represents a significant extension of the range of this species, previously documented only from two sites near Wilmington. Additional, more detailed surveys are called for.

>References

Basch, P. (1963) A review of the recent freshwater limpet snails of North America. Bull. Mus. Comp. Zool. Harvard, 129: 399-461. Burch, J. (1989) North American Freshwater Snails. Hamburg, MI, Malacological Publications.  Dillon, R. T. & J. J. Herman (2009) Genetics, shell morphology, and life history of the freshwater pulmonate limpets Ferrissia rivularis and Ferrissia fragilis.  J. Freshw. Ecol. 24: 261-271.  Fuller, S. L.F. (1977) Freshwater and terrestrial mollusks. pp 143-194 in Endangered and Threatened Plants and Animals of North Carolina (J. Cooper, S. Robinson, & J. Funderburg, Eds.). Raleigh, NC State Museum of Natural History. Scientific Council on Freshwater and Terrestrial Mollusks (1990) A report on the conservation status of North Carolina's freshwater and terrestrial molluscan fauna.