First description of parasitation by Aggregata octopiana in common octopus, Octopus vulgaris, in Canary Islands

Abstract

The negative effects that infections with the coccidian parasite Aggregata octopiana has in cephalopods is widely known. However, the assessment of this pathology is fundamental to optimize the intensive culture of octopus. In the present report a total of 35 octopuses were studied, 6 coming from the wild, 5 grown in land tanks, 11 grown in benthic sea cages and 13 grown in floating cages. Each octopus was individually identified by a microchip and fed a fresh diet based on discarded bogue and crab during two months for then being sacrificed and sampled. Experimental animals were weighed weekly to calculate their growing rate and, at the end of the trial, segments from intestine, stomach and gills were fixed in buffered formalin for their histopathological evaluation. Furthermore, caecum smears were studied in fresh and after Giemsa staining. In each studied group the prevalence of infection was up to 70%, being 100% in the case of animals grown in land tanks. Weight gain was high, around 38 g.day(-1), excepting for animals grown in land tanks (only 9 g.day(-1)). Sexual and asexual reproductive forms of this parasite were observed in studied organs, being macroscopically observed as white nodules distributed all along the digestive tract. Histologically, lesions observed in intestines consisted of a marked dilatation of lamina propria and presence of a moderate inflammatory reaction at intestinal villi, which were invaded by parasitic structures. In gills, parasites were observed both in epithelial and connective tissue, generating haemocytic infiltrates. This paper reports the first description of an apicomplexan of the genus Aggregata in Octopus vulgaris from northeastern central Atlantic waters and proves that growing of octopus in cages is optimal for this species.