Phylum HAPLOSPORIDIA Caullery & Mesnil, 1899

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Introduction

Haplosporidia are characterised by the formation of unicellular spores (without polar capsules or polar filaments) that contain a single sporoplasm and several dense organelles (known as haplosporosomes). Spores have an orifice covered by an operculum or occluded by a lingua plug. The spores are covered with filamentous ornaments that sometimes appear as tails. They occur as parasites of invertebrate hosts in which uninucleate cells undergo modified schizogony to give rise to multinucleate plasmodia which develop into sporonts and eventually differentiate into spores. Most are histozoic or coelozoic parasites of aquatic molluscs, annelids, crustaceans and helminths. Several species cause significant diseases and mortality in oysters around the world.

Haplosporidian and paramyxean parasites have recently been grouped together on the basis of their molecular phylogenetic similarities in the Phylum Ascetospora Sprague, 1979, emend. Cavalier-Smith, 2009, placed near the base of the Cercozoa Cavalier-Smith, 1998, emend. Adl et al., 2005 (cf. Adl et al. 2012).

Diagnosis

Unicellular protistan parasites, form unicellular spores without polar capsules or filaments.

General References

Adl, S.M., Simpson, A.G.B., Lane, C.E., Lukes, J., Bass, D., Bowser, S.S., Brown, M.W., Burki, F., Dunthorn, M., Hampl, V., Heiss, A., Hoppenrath, M., Lara, E., Le Gall, L., Lynn, D.H., McManus, H., Mitchell, E.A.D., Mozley-Stanridge, S.E., Parfrey, L.W., Pawlowski, J., Rueckert, S., Shadwick, L., Schoch, C.L., Smirnov, A. & Spiegel, F.W. 2012. The revised classification of eukaryotes. Journal of Eukaryotic Microbiology 59: 429-493

Caullery, M. & Mesnil, F. 1899. Sur le genera Aplosporidium (nov) et l'ordre nouveau des Aplosporidies. Comptes Rendus des Séances de la Societe de Biologie et de Ses Filiales 1 51: 789-791

Perkins, F.O. 1990. Phylum Haplosporidia. Chapt. 2. pp. 19-29 in Margulis, L., Corliss, J.O., Melkonian, M. & Chapman, D.J. (eds). Handbook of Protoctista. Boston : Jones & Bartlett Publishers.

Sprague, V. 1979. Classification of the Haplosporidia. pp. 40-44 in Perkins, F.O. (ed.). Haplosporidian and Haplosporidian-like Diseases of Shellfish. Special Bulletin. United States National Museum 44

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