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Diseases of Aquatic Organisms

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DAO 65:237-243 (2005)  -  doi:10.3354/dao065237

Ophryoglena hemophaga n. sp. (Ciliophora: Ophryoglenidae): a parasite of the digestive gland of zebra mussels Dreissena polymorpha

Daniel P. Molloy1,*, Denis H. Lynn2, Laure Giamberini3

1New York State Museum, The State Education Department, Cultural Education Center, Albany, New York 12230, USA
2Department of Zoology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
3Laboratoire Ecotoxicité et Santé Environnementale, CNRS UMR 7146, Université Paul Verlaine-Metz, Campus Bridoux,rue du Général Délestraint, 57070 Metz Cedex, France

ABSTRACT: Ophryoglena hemophaga n. sp. is described from a freshwater Dreissena polymorpha population in the Rhine delta of the Netherlands. This is the first ophryoglenine species (order Hymenostomatida, suborder Ophryoglenina) recorded as a molluscan parasite. As is typical of ciliates in the suborder Ophryoglenina, O. hemophaga exhibits a polymorphic life history with cystment and reproduction by palintomy. Trophonts were observed within digestive gland lumina, and zebra mussel hemocytes were present in some of their digestive vacuoles. The presence of a single, longitudinal tract of multiple contractile vacuoles represents its most unique feature and distinguishes it from all other described Ophryoglena spp. The number of somatic kineties of O. hemophaga (range 50 to 62) is also a distinguishing feature, since it is the lowest described from any Ophryoglena sp. Other characteristics of this species include: ovoid to elongate trophonts 96 to 288 µm in length, with an elongate macronucleus 41 to 65 µm in length; tomonts 50 to 150 µm in diameter producing a clear mucous cyst envelope, whose thickness is approximately half of the tomont diameter; elongated theronts 96 to 131 µm in length which emerge after 1 to 3 cell divisions taking 36 to 48 h at 20 ± 3°C. Protomonts and theronts are, respectively, negatively and positively phototactic—characteristics that likely aid in maintenance of infection in zebra mussel populations.
Erratum 1, Erratum 2

KEY WORDS: Contractile vacuoles · Trophont · Tomont · Theront · Zebra mussel · Palintomy · Phototaxis

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