The catastrophic collapse of the larval trematode component community in Charlie ' s Pond ( North Carolina ) - - Manuscript Draft

Abstract: ABSTRACT: In 1984, work on the parasite population and community ecology in the pulmonate snail, Helisoma anceps, was initiated in Charlie's Pond (North Carolina). Similar research on Physa gyrina was started in 1986. When study in the pond began in 1984, 8 species of larval trematodes were being shed from H. anceps. By far, the dominant species was Halipegus occidualis, with prevalences generally ~60%, except during mid-summer, when older snails were dying. For the other 7 trematode species being shed, prevalences were consistently less than 4%. By 2006, 18 species had been identified in H. anceps at one time or another. In 1986, Halipegus eccentricus was discovered in P. gyrina, with a prevalence of ~49%. Through 2006, 7 trematodes were found to be shedding cercariae from P. gyrina. Halipegus eccentricus disappeared from the pond in 1998. From March through November of 2012 and 2013, 1,292 H. anceps and 716 P. gyrina were collected, using collection protocols that were identical to those used from 1984 through 2006. In 2012, 5 trematode species, including H. occidualis, were present in H. anceps at one time or another. During the last part of the 2012 collecting season cercariae of just 2 species were being shed from H. anceps (and 1 from P. gyrina). In 2013, only cercariae of Haematoloechus longiplexus and Uvulifer ambloplitis were observed from H. anceps. The latter species was lost by 2014, and an echinostome was present (2.1%); a single snail was infected with H. longiplexus. Four species were being shed from P. gyrina, i.e., Echinoparyphium sp. (7.9%), Glypthelmins sp. (1.5%), Plagiorchis sp. (4.9%), and Posthodiplostomum sp. (7.4%). Rarefaction curves were generated for H. anceps shedding in 1984, 1988, 1989, 2002, 2006, and August of 2014. The data clearly indicate that species diversity was constantly declining over the 31-yr-period. We did