Hepatoxylon trichiuri (Cestoda: Trypanorhyncha) plerocercoids in cage-reared northern bluefin tuna, Thunnus thynnus (Osteichthyes: Scombridae)
Northern bluefin tuna (Thunnus thynnus) were caught by purse seine boats and brought to a farm for a rearing cycle of 1.5 years. Mortalities occurred in the first weeks of acclimatization at the facility. Parasitological examination revealed plerocercoids of the cestode Hepatoxylon trichiuri embedded in the stomach mucosa. The larvae were found in 28.4% of the fish and the mean abundance was 3.12 per fish. Histopathology revealed disseminated erosion at the site of attachment, atrophy of fundic glands, lymphocytic migration, and hyperplasia of connective tissue in the lamina propria. These symptoms, however, together with the parasite abundance, could not have triggered the mortalities. This is the first record of this parasite in northern bluefin tuna.
Les helminthes parasites des thons tropicaux
Il n’est pas possible à l’époque actuelle d’établir une récapitulation complète des espèces d’helminthes parasites des thons tropicaux, et cela pour deux raisons : la systématique exacte des thons est encore fort mal préciiée, le nombre des espèces décrites étant certainement trop élevé. Il semble en particulier que certains thons, à répartition sans doute cosmopolite, ont re$u des noms spécifiques différents, en fonction surtout de leur origine géographique, ou de très faibles variations morphologiques; chez ces hôtes souvent mal identifiés, ont été décrites de nombreuses espèces d’helminthes, parfois tellement voisines que l’on retenait justement la différence d’hôte comme critère d’identification.
Relationships among black marlin, Makaira indica, in Eastern Australian coastal waters, inferred from parasites.
Parasites of black marlin, Makaira indica, from Queensland coastal waters were examined in order to evaluate their usefulness as biological tags providing information on host movements. Sixty-three black marlin were sampled between 1987 and 1989 from five localities between Cape Moreton in southern Queensland and Lizard Island in the north. Black marlin carried 31 parasite taxa of which 21 were new host records, including one new species, Maricostula makairi Bruce & Cannon, 1989. Multi-dimensional scaling and cluster analysis of data on eight parasite taxa considered to be long-lived indicated that juvenile black marlin in Queensland coastal waters are isolated from the adults of Lizard Island. There was a tendency for parasite infections to increase with latitude within a cohort of juvenile fish, which is consistent with a hypothesis of southerly migration in coastal waters. Information from nine short-lived parasite taxa suggested that similar short-term movements by juveniles and adults, but with recently matured males at around 50 to 80 kg showing greater association with the adult population; these latter results were interpreted as, not a mixing of the juvenile and adult subpopulations, but an acquisition of short-lived infections by adults, similar to those of the juvenile marlin, during movement into shelf-edge water for spawning.