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Fungal Biol. 2014 Jul;118(7):544-58. doi: 10.1016/j.funbio.2014.01.007. Epub 2014 Feb 12.

Aquastella gen. nov.: a new genus of saprolegniaceous oomycete rotifer parasites related to Aphanomyces, with unique sporangial outgrowths.

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Division of Research & Collections, New York State Museum, New York State Education Department, Albany, NY 12230, USA; Department of Biological Sciences, State University of New York, 1400 Washington Avenue, Albany, NY 12222, USA. Electronic address:
135 Brodrick Road, Eastbourne BN22 9RA, East Sussex, UK.
Division of Research & Collections, New York State Museum, New York State Education Department, Albany, NY 12230, USA.
School of Biology, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA.
RNT Consulting, Ontario, Canada.
Department of Biology, Saint John's University, Collegeville, MN 56321, USA.
Université de Lorraine, CNRS UMR 7146, Campus Bridoux, Rue du Général Delestraint, F-57070 Metz, France.


The oomycete genus Aquastella is described to accommodate two new species of parasites of rotifers observed in Brooktrout Lake, New York State, USA. Three rotifer species--Keratella taurocephala, Polyarthra vulgaris, and Ploesoma truncatum--were infected, and this is the first report of oomycete infection in these species. Aquastella attenuata was specific to K. taurocephala and Aquastella acicularis was specific to P. vulgaris and P. truncatum. The occurrence of infections correlated with peak host population densities and rotifers were infected in the upper layers of the water column. Sequencing of 18S rRNA and phylogenetic analysis of both species placed them within the order Saprolegniales, in a clade closely related to Aphanomyces. The Aquastella species were morphologically distinct from other rotifer parasites as the developing sporangia penetrated out through the host body following its death to produce unique tapered outgrowths. Aquastella attenuata produced long, narrow, tapering, finger-like outgrowths, whilst A. acicularis produced shorter, spike-like outgrowths. We hypothesize that the outgrowths serve to deter predation and slow descent in the water column. Spore cleavage was intrasporangial with spore release through exit tubes. Aquastella attenuata produced primary zoospores, whereas A. acicularis released spherical primary aplanospores, more typical of other genera in the Aphanomyces clade.


Aquastella acicularis; Aquastella attenuata; Convergent evolution; Phylogenetic analysis; Saprolegniales

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