Fine Structure of Marteilia sydneyi sp. n.: Haplosporidan Pathogen of Australian Oysters

Abstract

AOSTnACT: A new species of oyster pathogen, Marteilia syd11eyi, from Australian oysters, Crassostrea commercialis, is described incorporaling light and electron micro~ropr obsrrvatious. The pathogen is a hnplosporidan w hich e,ists n.s a plasmodiwn in the oyste r hepatopnncreas. Upon sporulation, 8 to 16 uninuc lcate sporangial prlmordia a re internally cleaved (endogenously budded) from each plasmodium; thus c.-onver:;ion lo a sporangiosorus occurs. Each spornngium enlnrsres and internally cleaves into 2 or 3 spore primordia each of w hich, in turn, internally cleaves into 3 uninuclcalc sporoplnsms of graded sizes, the largest containing the \ mailer 2 in u va cuole and the inte m1ediale-~izcd one containing the smallest in a vacuole. The spore wall Is continuous without an orifice ur upt•rculum.

Breeding for QX disease resistance negatively selects one form of the defensive enzyme, phenoloxidase, in Sydney rock oysters

“…The homogenates were diluted 1:10 in FSW and M. sydneyi sporonts were stained with KOVA (Hycor Biomedical Inc., California, USA) so that their frequency could be calculated using a haemocytometer according to the method of Peters and Raftos [6]. The identification of M. sydneyi was based on previous descriptions [22,23].…”

Marteiliosis in molluscs: A review

“…Another species of the genus Marteilia, M. maurini, was described in blue and Mediterranean mussels, Mytilus galloprovincialis, M. edulis, from France Auffret and Poder 1985). In Australia, Marteilia sydneyi was described in the Sydney rock oyster, Saccostrea glomerata (see Perkins and Wolf 1976). Lastly, the species Marteilia christenseni was described in peppery furrow, Scrobicularia [piperata] plana by Comps (1983) on the Atlantic coast of France, and M. lengehi in the hooded oyster, Saccostrea cucullata, from the Persian Gulf (Comps 1976) and, possibly, Australia (Hine 1996).…”

“…Marteilia refringens is the causative agent of Aber disease which provokes mass mortality of the flat oyster, Ostrea edulis, in Europe (Alderman 1979;Grizel 1985). Similarly, Marteilia sydneyi is responsible for QX disease in Sydney rock oyster, Saccostrea glomerata, in Australia (Perkins and Wolf 1976;Adlard and Ernst 1995). These agents are regarded as major concerns for mollusc aquaculture and are listed by the Office International des Epizooties (OIE 2003).…”

Molecular detection of Marteilia sydneyi, pathogen of Sydney rock oysters

“…and reported poor hybridisation of mature spores of 2 haplosporidian species, Haplospondiurn nelsoni and Minchinia teredinis, and attributed this to the inability of either (or both) the probe or anti digoxygenin antibody to penetrate the thick spore wall. Impermeability of the spore wall in Marteilia spp., described as a 'thin envelope' (Desportes 1984) which does not variegate as the spore matures (Perkins & Wolf 1976), is an unlikely explanation for differences in probe and antibody penetration in immature and mature spores in this study. Concentric myelin whorls, composed of degraded extraspore cytoplasm, progressively enclose the spore as it matures within the sporont (Perkins & Wolf 1976); however, given that fixatives and embedding agents easily penetrate mature spores of M. sydneyi for ultrastructural study and are excluded in preparations of mature spores of Haplosporidia (Perkins 1990), the membranes should not compromise p r o h e or an!ihcrly penetration.…”

“…Although current management strategies exist to keep stock losses within manageable limits and prevent further geographic spread of the disease, potential control is hindered by the incomplete understanding of the life cycle of this pathogen. Development and ultrastructure of presporulating and sporulating stages in the oyster host are described (Perkins & Wolf 1976); however, the stage infective to the oyster and its origin are unknown. Failure to infect oysters experimentally with mature spores (Lester 1986) and recent evidence which suggests a limited period of viability of spores in seawater (Wesche et al 1999) have implicated the involvement of an intermediate host.…”