engleski

Ceratothoa oestroides: The beauty within the beast

Ceratothoa oestroides (Risso, 1816), an obligate crustacean isopod parasite in marine fish, causes many issues in aquaculture in some parts of Mediterranean, inducing tissue damage at the site of parasitation (tongue), growth defects, decrease in mean host weight and size, as well as increase in mortalities in the population of wild fish. A generalist in the wild, in aquaculture is known to infect cage reared sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) where fish density facilitates transmission between individuals. In some countries it is efficiently treated by chemotherapeutics, while in others it is manually extracted during vaccination or sorting for the market. Nevertheless, understanding the life cycle and behavioral mechanism of C. oestroides could help us in establishing novel strategies in preventing and controlling infection outbreaks. Live sea bass (300 g) infected with paired isopods were transported from the fish farm to Institute of Oceanography and Fisheries, where they were kept in experimental tanks (2m3) for 46 days (17.6 ⁰C - 24⁰ C) before releasing F1 generation. Infective pulli stage (F1) were harvested immediately upon release from the female marsupium and were manually transferred to the buccal cavity of live sea bass (14 g). After 112 days (20.0 ⁰C – 25 ⁰C) female released pulli – F2 generation. The life cycle of the parasite was successfully repeated over two passages (F2 generation) in the new hosts. Some of parasite’s developmental stages were kept for transmission electron microscopy (TEM), assessment of feeding apparatus ontogeny and artificial feeding trials. Adult females fed by blood survived for 30 days in experimental system and a development of embryos was observed. Pulli kept in different feeding systems survived the same length of time, but did not undergo any development, surviving upon their vitelline reserves. Still many factors need to be elucidated before we understand more clearly the developmental triggers that enable infection in fish.

Ceratothoa oestroides ; Dicentrarchus labrax ; experimental infection ; artificial feeding ; life cycle

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