engleski

Microparasites of reared bluefin tuna (Thunnus thynnus)

Prasitofauna of blufin tuna is composed of high number of species that in optimal farming conditions it shows no tendency for intensive proliferation, and thus does not represent a real health threat. It is noteworthy that highly pathogenic parasites implicated in mortalities of southern bluefin tuna (T. maccoyii) reared in Australia, the scuticociliate Uronema nigricans and trematode Cardicola forsteri, were not isolated from Adriatic reared stocks (Nowak B et al, Bulletin of the European Association of Fish Pathologists, 26: 38-42). Over the period of 2002-2006, parasitological examination was done on newly caught tuna specimens, one/ two-years-reared fish, harvested tuna and occasional mortalities. While the total number of isolated parasite species was 23, composed mostly of didymozoid digenea, only two species were microparasitic: myxosporidian Ceratomyxa thunni and microsporidian of still undesignated phylogeny Microsporidia sp. In order to have a better insight of their morphology, TEM was done on parasitic cysts and bile fluid embedded in Durcopan resin. The ultrathin sections (0.05 µ ; ; m) were made from the chosen area, stained with uranyl acetate and lead citrate and examined on microscope FEI Morgagni 268D. 28ssu rDNA of two microparasites species was amplified, sequenced and the product was aligned to available GeneBank sequences showing, in case of Microsporidia sp., discrepancy between morphology and genetic provenience. Calculated prevalences and abundances of two species were low (Bush AO et al, Journal of Parasitology, 83: 575-583). No pathology could be related to isolated parasites.

microparasites ; bluefin tuna ; Thunnus thynnus

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