title: The influence of trematode metacercariae on the individual fecundity of Bithynia troscheli (Gastropnoda: Bithyniidlae).
abstract: Fifteen trematode species belonging to seven families parasitizing the females of Bithynia troscheli (Paasch, 1842) at metacercarial stage, were recorded in Kargat River (Lake Chany, South of West Siberia, Russia). The breeding mollusk females have less metacercarial diversity (9 species vs. 15) and lower mean parasite abundance, comparing to non-ovigerous mollusks. The hypothesis of the metacercarial influence on individual fecundity of aquatic gastropods was tested. The individual fecundit pariameters of the-B. troscheli females, uninfected and infected with the trematode metacercariae belonging to fam. Echinostomatidae, Cyathocotilidae, Strigeidae, Cyclocoelidae, were compared. The percentage of the breeding B. troscheli females--was less and their fecundity parameters were lower for the hosts infected (with the Strigeidae or Cyclocoelidae metacercariae) comparing to non-infected ones. Trematode metacercariae found in the mantle or somatic musculature had no significant effects on the fecundity of the host. However, our results showed that trematode metacercariae affect the reproduction of B. troscheli in dual ways. All fecundity parameters of the mollusk females with the high infection rate were, significantly lower than those for uninfected females: the percentage of fecund females (chi2 = 6.73 ,p < 0.01), number of clutches per female, number of egg capsules per clutch and number of normal egg capsules per female (Tukey HSD, p < 0.001). Although the females with-low intensity of metacercarial infection lay egg clutches significantly more frequently than uninfected ones (chi2 = = 4.18, P = 0.04); the fecundity parameters were approximately equal for both groups of the mollusk females. These pioneer results prove the reality of influence of metacercariae on the individual fecundity of aquatic gastropods. The regulatory population mechanisms that may compensate the host reproduction loss caused by metacercaria, are discussed.
authors.forename: E A
authors.initials: EA
authors.lastname: Serbina
mesh_terms: D000818:Animals; D004450:Echinostomatidae / Q000502:physiology*; D005260:Female; D005298:Fertility; D049851:Gastropoda / Q000469:parasitology*; D058488:Metacercariae / Q000502:physiology*; D012800:Siberia