Granovitch A.I., A.M.Gorbushin, 1995 The differences between infestation rates of females and males in intertidal snails from gen. Littorina and Hydrobia infected by trematode parthenites.

Parasitologia, 29(3), 167-178 [In Russian]

Abstract. The distribution of trematode parasites was investigated in 12 populations of Littorina saxatilis, L.obtusata, Hydrobia ulvae and H.ventrosa in White Sea. Differences in infection level were found in different populations of the same host species from few percents to more than 60%.

The quantitative differences of infection prevalence in snails of different sex were found in some populations of the hosts. However there are no differences of this kind in other populations of the same species of snails.

More sophisticated treatment of the syntopic populations of L.saxatilis and L.obtusata (western spit of southern inlet of Ryazhkov island in North Archipelago, Kandalakshsky Bay) was carried out over a period of 8 years - from 1982 to 1989. The infection prevalence of the snails by the most species of trematodes (8 species) is low. There are no differences in male female infection prevalence connected with these parasites over the all period of investigation. The infection prevalence of L.obtusata and L.saxatilis by trematodes Microphallus piriformes varies from year to year more than twice and may be as much as 50%. It has been just the years of peak of infection prevalence (by this parasite), when the levels of hosts males and females infection are differ (P<0.05) (1985 - for L.obtusata and 1984 for L.saxatilis).

The distribution of M.piriformes in snails of different age was considered separately for males and females during 8 years. High levels of infection in populations of L.saxatilis and L.obtusata were found to be connected with infection of snails in all age groups, but those of different ages were infected differently in the certain year. This index is also differ for the same age groups of the hosts but in different years (due to dynamics of the level of infection from year to year). In the same time general