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Morphology and molecular phylogeny of Haplozoon praxillellae n. sp. (Dinoflagellata): A novel intestinal parasite of the maldanid polychaete Praxillella pacifica Berkeley

Rueckert, Sonja; Leander, Brian S.


Brian S. Leander


The genus Haplozoon comprises a group of endoparasites infecting the intestines of polychaete worms. Comparative studies using light microscopy, scanning and transmission electron microscopy, and small subunit rDNA have shown that these organisms are very unusual dinoflagellates. To date, there is only one species known from the Pacific Ocean, namely Haplozoon axiothellae Siebert. In this study, we describe Haplozoon praxillellae n. sp. from the intestine of the Pacific maldanid polychaete Praxillella pacifica Berkeley. The parasites are relatively small, oblong and about 35–125 μm in length, consisting of the trophocyte (anterior-most compartment), rectangular gonocytes and bulbous sporocytes. The trophocyte bears an attachment apparatus with a prominent ‘suction disc’ and numerous stylets. We were able to detect spherical vesicles near the ventral surface of each gonocyte. The whole organism is covered with thecal barbs of different shape and size, except for the caudal end of the posterior-most sporocyte, which is instead covered with hexagonal or pentagonal alveoli. A continuous membrane encloses the whole pseudocolony. Molecular phylogenetic data, host specificity and morphological differences clearly distinguish H. praxillellae n. sp. from H. axiothellae.

Journal Article Type Article
Publication Date 2008-11
Deposit Date Sep 25, 2013
Print ISSN 0932-4739
Electronic ISSN 1618-0429
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 44
Issue 4
Pages 299-307
Keywords Microbiology
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