Marteiliasis affecting cultured mussels Mytilus galloprovincialis of Galioa (NW Span). I. Etiology, chases of the infection, and temporal and spatial variability in prevalence

Abstract

The histological location, morphological fedtures and ultrastructural characters of the sporulation of the parasite causing Marteiliasis affecting cultured mussels in Galicia fit the characteristics defined for the type species Marteilia relringens The early stages of the infection are confined to the host stomach epithelium. The spreading of the parasites through the host digestive diverticula involves a n exponential increase in the number of parasites as the infection progresses, suggesting the occurrence of merogony, in addition to the well known sporulation. The infection usually triggers a host hemocytic reaction that may slow down or even stop the infection at times. The study of 5 zones of culture disclosed great spatial variability in the prevalence of Marteiliasis on mussels throughout the bays of Galicia, including a n area in which no infection was detected. The culture zones located within the bays showed higher prevalences than those located outside. There was no significant difference in the intensity of the infections among the affected zones Sporulation occurred throughout the year Several peaks of both prevalence and occurrence of heavy ~nfections took place every year. Considering the areas affected by Marteiliasis, the higher the prevalence of the infect~on the higher the mortality. In some of the studied zones, mortality was significant for the mussel farming industry.

Experimental transmission of Marteilia refringens with special consideration of its life cycle

“…In Europe, M. refringens has been observed in Ostrea edulis, 0. angasi, 0 . chilensis (Grizel et al 1974, Bougrier et al 1986, and in Mytilus edulis and M. galloprovincialis (Tig6 & Rabouin 1976, ClaverDerqui 1990, Villalba et al 1993. M. refringens cells were also found in the Pacific cup oyster Crassostrea gigas (Cahour 1979).…”

Marteiliosis in molluscs: A review

“…As the infection progresses, variable amounts of haemocyte infiltration may be observed in primary and secondary digestive tubules (Alderman 1979;Robledo and Figueras 1995). In Mytilus galloprovincialis, focal and massive concentrations of haemocytes described as granulocytomas may occur along with tissue necrosis (Villalba et al 1993a). Infection by M. refringens may cause significant increase of haemocytes in the haemolymph (Carballal et al 1998).…”

Ultrastructural characterisation of Marteilia species (Paramyxea) from Ostrea edulis, Mytilus edulis and Mytilus galloprovincialis in Europe

“…The diagnosis of the 2 species of Marteilia found in Europe (M. refringens and M. maurini ) currently requires analysis of the ultrastructural characteristics and consideration of the host specificity (Grizel 1974, Comps et al 1982. Indeed, the only ultrastructural features selected by Comps et al (1982) to distinguish the 2 species were subtle differences in haplosporosome shape and the 'existence of a multimembranous envelope next to the spore wall'.The recent discovery of Marteilia refringens in Mytilus galloprovincialis (Villalba et al 1993 has raised some doubt that Marteilia maurini, which was described as the only Marteilia species parasitizing mussels, is a distinct species from M. refringens. Experimental transmission of M. refringens between members of the same or differing host species has been unsuccessful, although it has been attempted in a number of experiments under differing conditions (Figueras & Robledo 1993, Berthe et al 1998.…”