Spore ornamentation of Minchinia occulta n. sp. (Haplosporidia) in rock oysters Saccostrea cuccullata (Born, 1778)

Abstract

Phone 61 08 9360 24792 ABSTRACT A Minchinia sp. (Haplosporidia: Haplosporidiidae) parasite was identified infecting rock oysters and morphologically described by Hine and Thorne (2002) using light microscopy and transmission electron microscopy (TEM).The parasite was associated with up to 80% mortality in the host species and it is suspected the parasite would be a major impediment to the development of a tropical rock oyster aquaculture industry in northern Western Australia.However, attempts to identify the parasite following the development of a specific probe for Haplosporidium nelsoni were unsuccessful. The SSU region of the parasite's rRNA gene was later characterised in our laboratory and an in situ hybridisation assay for the parasite was developed. This paper names the parasite as Minchinia occulta n sp. and morphologically describes the parasite using histology, scanning electron microscopy and transmission electron microscopy. The non-spore stages were unusual in that they consisted primarily of intracellular, uninucleate stages reminiscent of Bonamia spp. The parasite's spores were ovoid to circular shaped and measured 4.5 μm -5.0 μm x 3.5 -4.1 μm in size. The nucleus of the sporoplasm measured 1.5 -2.3 μm and was centrally located. The spores were covered in a branching network of microtubule-like structures that may degrade as the spore matures.

Minchinia mercenariae n. sp. (Haplosporidia) in the Hard Clam Mercenaria mercenaria: Implications of a Rare Parasite in a Commercially Important Host

“…The type species, M. chitonis , has two long appendages at each end of the spore (Ball 1980), M. tapetis has only a single long aboral tail (Azevedo 2001), and M. teredinis has four unbranched appendages (McGovern and Burreson 1990). Another newly described Minchinia sp., M. occulta , is covered with a network of branching, microtubule‐like structures (Bearham et al 2008a). The spore ornamentation of M. dentali , a parasite of scaphopods in the French Mediterranean Sea, is unknown.…”

Inter-relationships of haplosporidians deduced from ultrastructural studies

“…Similarly, NM-BG were also not reported from Minchinia occulta (Hine & Thorne 2002, Bearham et al 2008b), but vegetative stages were rarely observed. Indentations in the nuclear surface (INS) have been reported in the NZAP and 3 ostreid haplosporidians (Table 4).…”

“…reported from rock oysters Saccostrea cuccullata by Hine & Thorne (2002) was reclassified as Minchinia sp. on the basis of a molecular study (Bearham et al 2007), and described as M. occulta Bearham et al (2008b).…”

“…These may be transient and associated with exsporulation (Azevedo & Corral 1989), but they have not been observed on the operculae of Haplosporidium spp. or M. occulta (Hine & Thorne 2002, Bearham et al 2008b). …”

“…Minchinia spp. infect different classes of molluscs: M. dentali in a scaphopod, M. chitonis in a polyplacophoran, and M. teredinis, M. occulta (Bearham et al 2008b) and Minchinia sp. (Comps & Tigé 1997) in different families of bivalves.…”