Influence of trematodes on the demography of Littorina saxatilis (Gastropoda:Prosobranchia:Littorinidae) in the White Sea

Abstract

Five populations of the rough winkle Littorina saxatilis (Olivi) with different levels of trematode infection were investigated in the White Sea, NW Russia: 2 control populations N1 and N2 (ca 5'K) infection), 1 moderately infected population M (ca 10 to 15% infection) and 2 heavily infected populations H1 and H2 (50 to 80% infection). Trematode prevalence was the lowest in snails collected from macrophytes, intermediate on gravel and highest on stone surfaces at all collection sites. The distribution of infection in different age groups of snails was random in the control populations, but prevalence increased with age in moderately and heavily infected populations. Demographic structure was variable. The following parameters were typical for all populations regardless of infection level: (1) total sex ratios were close to 1:l or biased slightly towards females; (2) the relative abundance of males decreased with the age of snails; (3) no sex-specific ditterences in infection prevalence were found in any population, and (4) females became mature at 3 to 4 yr However, the following demographic parameters showed significant differences that were correlated with trematode ~nfection: (1) fewer juveniles were found in populations H1 and H2, probably a result of reduced recruitment due to severe infection; and (2) fecundity of uninfected females increased with the increase in trematode infection at the collection sites and was the lowest in populations N1 and N2, intermediate in population M and the highest in population HI. These results suggest an adaptation that ensures periwinkle survival under conditions of heavy infection pressure.

Parasitic castration in Concholepas concholepas (Gastropoda:Muricidae) due to a larval digenean in northern Chile

“…As in other mollusks (Sokolova 1995, Taskinen & Valtonen 1995, there were no significant differences in prevalence of infection between male and female mollusks. A direct relationship between prevalence of infection and size of molluskan host has been described for infection by larval digeneans (Sousa 1983, Taskinen & Valtonen 1995, and adult digeneans (Oliva & Diaz 1988, 1992.…”

“…In contrast to other gastropod-parasite systems with sporocysts or rediae as the infective stage, Concholepas concholepas is infected by only 1 parasitic digenean. (Sullivan et al 1985, Fernandez & Esch 1991a, Jokela & Lively 1995, Sokolova 1995. Parasites of other marine gastropods from this zone are also only infected by 1 parasitic species; this has been found to be the case in 5 species of key-hole limpets Fissurella spp.…”

Physiology and lipid metabolism of Littorina saxatilis infected with trematodes

“…Despite often heavy infestation by trematodes, gastropods in tidal zone areas are often numerous. In the White Sea, densities of trematodeinfected L. saxatilis can amount to thousands of individuals m -2 (Sokolova 1995). The effects that parasites can inflict on host physiology remain to some extent ambiguous; it is particularly unclear to what extent parasites stimulate parasitism.…”

Estrategias de transmisión de digeneos parásitos que utilizan gasterópodos como hospedadores intermediarios en la costa patagónica

“…La talla es una de los principales factores que afectan la prevalencia de parásitos y ha sido ampliamente citado en la bibliografía (e.g. Baudoin, 1975;Granovitch, 1992;Jokela & Lively, 1995;Sokolova, 1995;Poulin & Mouristen, 2003;. Sin embargo, algunos trabajos han registrado que no existen diferencias significativas de prevalencia entre sexos (Ginetsinkaya, 1988;Oliva & Diaz, 1988;Sokolova, 1995).…”

“…Baudoin, 1975;Granovitch, 1992;Jokela & Lively, 1995;Sokolova, 1995;Poulin & Mouristen, 2003;. Sin embargo, algunos trabajos han registrado que no existen diferencias significativas de prevalencia entre sexos (Ginetsinkaya, 1988;Oliva & Diaz, 1988;Sokolova, 1995). En la mayoría de los casos, cuando se registran diferencias de la prevalencia entre sexos suele deberse a variaciones en la abundancia de hospedadores de cada sexo, a diferencias de tallas o de comportamiento etre sexos, teniendo los sexos más abundantes o de tallas más grandes mayor probabilidad de infección (Ginetsinkaya, 1988;Granovitch, 1992).…”