The effect of trematode parthenites on the individual fecundity of Bithynia troscheli (Prosobranchia: Bithyniidae)

Abstract

AbstractWe studied the long-term infection of Bithynia troscheli (Paasch, 1842) snails with trematodes and estimated the influence of trematode parthenites on the individual fecundity of female snails from the Kargat River (Chany Lake, Russia). The prevalence of B. troscheli females infected by trematode parthenites varied from 7.12% to 17.35% in different years. Eleven redioid species from 5 families and 9 sporocystoid species from 5 families of trematodes were found during this investigation. Snails’ fecundity was analysed in relation to the type of infection (redioid or sporocystoid species). Fecund females of B. troscheli were uninfected or they had pre-patent infections from 5 families of trematodes (Psilostomidae, Notocotylidae, Prosthogonimidae, Lecithodendriidae, and Cyathocotylidae). 89.9% of infected B. troscheli females were infertile. Moreover, 13.57% and 1.29% egg capsules (of infected and uninfected females, respectively) were without embryos (χ2 = 323.24, p<0.001). The results of the two-way analysis of variability confirmed that trematode parthenites influenced significantly the individual fecundity of B. troscheli. The age of B. troscheli females alone did not alter the individual fecundity, however age in combination with infection by tremathode parthenites influenced significantly the number of normal egg capsules. We also found that under unfavorable environmental conditions the proportion of fertile females increased by 23.7% among uninfected and by 219% among infected females.