Myxozoan parasites of the European sea bass, Dicentrarchus labrax (Teleostei: Moronidae): Correlates of infections at the micro- and macroenvironment scales

Infections with myxozoan parasites are a source of concern for fish farm owners, as they can lead to significant economic losses. Owing to such potential detrimental impact, a comprehensive body of knowledge on myxozoans is required and, in this regard, elucidating different aspects of their ecology at the micro- and macroenvironment-level scales is crucial. The present study addresses the correlates of infections at both level-scales, for species of myxozoans occurring in Dicentrarchus labrax (Teleostei: Moronidae), an economically important species of fish for the aquaculture industry. Infection data for Sphaerospora dicentrarchi and S. testicularis (Myxozoa: Sphaerosporidae), and Ceratomyxa diplodae and C. labracis (Myxozoa: Ceratomyxidae), obtained from a total of 764 fish from wild (N = 373) and cultured (N = 391) environments, were used in the analyses. The mean prevalences of infection were 79.8% for S. dicentrarchi, 6.2% for S. testicularis and 21.7% for Ceratomyxa spp. At the microenvironment-level scale, a significant relationship was detected between the host sex, age, total weight and length and the prevalences of infection. At the macroenvironment-level scale, the prevalence of S. dicentrarchi was higher in wild than in cultured fish, contrary to that observed for Ceratomyxa spp. The results obtained from the Generalized Linear Model analysis suggest that, the control of the environmental variables which influence the occurrence of infection constitutes a crucial prophilatic measure in the minimization of economic losses occurring in fish farming systems.