Immune response of sharpsnout seabream (Diplodus puntazzo, Cetti 1777) to Enteromyxum leei

E. leei affects at least 25 fish species but it represents a production limiting factor most of all for sharpnout seabream, causing high mortality during the first year of rearing (Diamant, 1995; Athanassopoulou et al., 1999). The knowledge on the immune response of sharpsnout seabream (Diplodus puntazzo, Cetti 1777) is lacking, even if recently some innate immune parameters were studied owing to experimental myxozoan transmission in different marine species (Karagouni et al., 2005; Golomazou et al., 2006). In particular the innate immune response against E. scophthalmi was studied in turbot (Scophthalmus maximus) (Sitjà-Bobadilla et al., 2006). The aim of this study was to evaluate serum complement and lysozyme activity, serum protein, peroxidase and immunoglobulin content in physiological conditions and during E. leei infection. Moreover the morphometry of peripheral blood leukocytes and the differential leucocyte counts were investigated on blood smears. Fish collected during spontaneous disease outbreaks, occurring in Italian fish farms, and a healthy fish group (control) were submitted to the immunological analysis. Lymphocytes, neutrophilic, acidophilic and occasionally basophilic granulocytes and monocyte-macrophages have been differentiated in peripheral blood of sharpsnout seabream. In the light of the morphological findings, a cell population resambling the mammalian natural killer cells has been observed. The serum immunological parameters surveyed throughout E. leei outbreaks in this species will be discussed.