A Mark-Recapture Study of Trematode Parasitism in Overwintered Helisoma anceps (Pulmonata), with Special Reference to Halipegus occidualis (Hemiuridae).

• Author(s) / Creator(s)

  • Shostak, A.W.
  • Esch, G.W.
  • Goater, T.M.
  • Williams, J.A.

• A collection of 556 snails, Helisoma anceps, was made from a pond in the Piedmont area of North Carolina during October 1987. Snails were measured and assayed for trematode parasitism, and then 500 randomly selected individuals were marked and returned to the pond. Collections made between 23 March and 12 July 1988 resulted in recapture of 86 marked snails. Five trematode species were present in the fall collection, dominated by the hemiurid Halipegus occidualis (present in 31.5% of all snails, and 84.5% of infected snails). Antagonistic interactions between H. occidualis and other trematodes were indicated by a lower proportion of multiple-species infections in the fall collection than predicted from trematode prevalences and snail size distribution. Spring collections resulted in recapture of 31 snails that had patent infections in the fall collection. Of these, 7 of 27 previously infected with H. occidualis no longer harbored patent infections, nor did 2 of 3 previously infected with Megalodiscus temperatus, or the single recaptured snail that previously had a patent infection with Diplostomulums cheuringi. Necropsy of 5 of 7 snails previously infected with H. occidualis revealed an intact ovotestis and no parasites, confirming loss of infection and reversal of parasitic castration. The number of new patent infections increased markedly between late March and early June, suggesting that acquisition of new infections commenced soon after snails emerged from the substratum in early March. Snail survival over the winter was independent of parasitic infection. Growth rates of snails harboring H . occidualis before and after the winter were similar to uninfected snails, but snails that became patent subsequent to the fall collection grew less than predicted. The consistency observed for fall and spring prevalences of H. occidualis reflects a dynamic balance among processes that tend to increase prevalence and others that tend to decrease it.

• Date created

  1989

• Subjects / Keywords

  • North Carolina
  • Parasitic infections
  • Helisoma anceps

• Type of Item

  Article (Published)

• DOI

  https://doi.org/10.7939/R38P5VM5Z

• License

  Copyright American Society of Parasitologists 1989