Ecological comments on the intestinal helminths of the rabbitfish Siganusrivulatus (Teleostei, Siganidae) from the northern Red Sea
Between May and September 2006, 640 specimens of the rabbitfish Siganusrivulatus Forsskal (Teleostei, Siganidae) were examined for infections with intestinal helminths.These fishes were caught in the Red Sea off the coast of Sharm El-Sheikh, South Sinai, Egypt,examined in a field laboratory and separated into three size groups of regular length intervals.Only three species of helminths were recovered: the trematode Gyliauchen volubilis Nagaty, 1956(Gyliauchenidae Fukui, 1929), the acanthocephalan Sclerocollum rubrimaris Schmidt et Paperna, 1978(Cavisomidae Meyer, 1932) and the nematode Procamallanus elatensis Fusco et Overstreet, 1979(Cucullanidae Cobbold, 1864). The distribution of these helminths along the intestine of S.rivulatus, in all patterns of single and concurrent infections and the corresponding prevalences andintensities of infection in the different size groups of the fish were recorded. In singleinfections, each parasite species was found distributed in a well-defined fundamental niche alongthe intestine of Siganus rivulatus, and a distinct partial overlap between the niches of G.volubilis and Sclerocollum rubrimaris was observed. In concurrent infections with these two species,their fundamental niches were significantly reduced, probably being affected by interactive sitesegregation and individuals of each species were found segregated in a restricted realised niche. Inall other patterns of concurrent infections, each parasite species was normally found in itsoriginal fundamental niche. The prevalences of these parasites in the fish examined were relativelylow and somewhat similar. In all patterns of single and concurrent infections, the intensity ofinfection was directly related to fish size. In concurrent infection with G. volubilis and S.rubrimaris, a significant decline was observed in the intensities of both species in the differentsize groups of the fish, but, in all other patterns of concurrent infections, no significant changein intensity was observed. These observations suggest that the interaction between G. volubilis andS. rubrimaris is probably a negative and symmetrical one. The mode of transmission of theseparasites to the fish is also discussed.
Hassanine, RMES Al-Jahdali, MO
Assiut Univ, New Valley Fac Educ, Dept Sci and Math, El Kharga, New Valley,Egypt; Jeddah Teachers Coll, Dept Sci, Jeddah, Saudi Arabia
Intestinal helminths interactive site segregation fish Siganus rivulatus Red Sea SITE SEGREGATION FISH COMMUNITIES PARASITES POPULATIONS HOST RHADINORHYNCHIDAE ACANTHOCEPHALANS GORGORHYNCHINAE AGGREGATION
