Mate finding in the isopod parasite Ceratothoa oestroides (Risso, 1816) in an aquaculture environment: A case study in the sea bass Dicentrarchus labrax (Linnaeus, 1758)

Abstract

The purpose of this in situ study was to determine the pattern of protandrous hermaphrodite Ceratothoa oestroides infestation in sea bass with respect to parasite sexual behaviour. Sea bass (N = 618) were divided into six net cages which presented three experimental groups. Group 1 represented infected fish, where female parasites were manually removed and male parasites were left in the buccal cavity of fish. Group 2 represented infected fish where both female and male parasites were removed, and group 3 represented uninfected fish (i.e., the control group). The duration of the experiment was 865.47 degree days (ºD), and average sea bass mortality rate was 11.97 %. No mature C. oestroides females were found at the end of the experiment. Fish in cages with removed female parasites (group 1) had a statistically higher number of parasites in pairs at the end of the experiment, compared to the group where all parasites - both males and females - were removed (group 2) and control group (group 3) (P < 0.005). Female parasites from group 1, being larger and older, had more success in mate finding. These results suggest that the female parasite uses some method of communication to attract the pulli II, i.e., the future male parasite, necessary for reproduction. Because there is a lack of parasite biology studies, especially in situ, our data on reproduction and mating behaviour of C. oestroides could help in the development of overall parasitic removal procedures and health management in aquaculture.