Abundance/host size relationship in a fish trematode community.
The abundance of six species of trematodes: Aphanurus stossichi, Bacciger israelensis, Diphterostomum israelense, Plagioporus idoneus, Leprocreadium album and L. pegorchis, parasitic in the digestive tract of marine teleostei (Sparidae) collected near Jounieh (east Mediterranean), was analysed as a function of the host-size. In two parasite/host systems, infections were observed from the lowest size classes of the sample, with a clear tendency to an increase of abundance in older fish. In four others, parasites appear only above a rather high threshold class, young individuals never being infected. In the last three parasite/host systems, host invasion may occur early or late, but infection decreases above a well defined size class, old fishes rarely or never being infected. A given trematode species, when parasitizing several host species, shows similar abundance/host size relationships, e.g., P. idoneus in Diplodus vulgaris and Oblada melanura. When more than one species of trematode infects a single host species, curves can be markedly distinct; for instance, L. pegorchis was collected from Pagellus erythrinus below 15 cm. whereas D. israelense parasitized the same fish approximately above the same size. There is no evidence that such a replacement of one trematode by another in the course of host growth is a result of inter-specific competition.
Saad-Fares
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Centre de Recherches Marines, Jounieh, Liban.
Combes
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D000818:Animals; D001824:Body Constitution; D005393:Fish Diseases / Q000453:epidemiology*; D006790:Host-Parasite Interactions; D010473:Perciformes / Q000469:parasitology*; D014200:Trematoda / Q000254:growth & development*; D014201:Trematode Infections / Q000453:epidemiology / Q000662:veterinary*