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Impact of parasitism and intersexuality on Mediterranean populations of Paracalanus parvus (Copepoda: Calanoida)

1987; Inter-Research; Volume: 3; Linguagem: Inglês

10.3354/dao003029

1616-1580

A lanora, M.G. Mazzocchi, Bruno Scotto di Carlo,

Genetic diversity and population structure

The incidence of parasitism and intersexuality in the dominant coastal copepod Paracalanus p a n w s was studied from 1984 to 1986 at a fixed station in the Gulf of Naples, Italy.Parasitic dinoflagellates belonging to the genera Atelodnium and Blastodlnium were the most plentiful forms respectively parasitizing the coelomic cavity and gut of their hosts.Infection by species of Atelodinium, the more common of the 2 parasitic groups, seems to be fatal.Parasitized individuals show striking morphological changes in shape and color as well as behavioral anomalies in swimming mode that reflect their poor physical condition.Infection by Blastodinium species is less devastating and does not seem to cause major structural or behavioural n~odifications.Both groups of parasites induce sexual castration in their hosts.Individuals infected by Atelodinium were seasonal in occurrence with highest abundances corresponding to a decline in P. parvus stocks suggesting a strong inverse relationship in the presence of parasites and their hosts.Infection was greatest for juveniles (up to 30 9") as opposed to females (8 %) and completely lacking in males.A strong correlation was also observed between the incidence of intersexes and females parasitized by Atelodinium, 20 '10 of which showed a modification of the P5 approximating that of juvenile and adult males.Most intersexes did not host internal parasites and only rarely were parasitized by Blastodinium suggesting early infection and later abandonment of the host by parasites of the digestive tract.Data are given on the incidence of intersexes in a number of coastal Mediterranean regions.These are discussed in relatlon to the possible role of parasitism in regulating seasonal fluctuations in species stocks in coastal communities.