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 aciculariswas 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. acicularisreleased spherical primary aplanospores, more typical of other genera in the Aphanomyces clade.
NOTICE: this is the author’s version of a work that was accepted for publication in Fungal Biology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Fungal Biology 118(7) (2014). DOI: 10.1016/j.funbio.2014.01.007.
Figures associated with this document are available for download as separate files at http://digitalcommons.csbsju.edu/biology_pubs/63/.
Molloy DP, Glockling SL, Siegfried CA, Beakes GW, James TY, Mastitsky SE, Wurdak ES, Giamberini L, Gaylo MJ, Nemeth MJ. 2014. Aquastella gen. nov.: A new genus of saprolegniaceous oomycete rotifer parasites related to Aphanomyces, with unique sporangial outgrowths. Fungal Biology 118(7): 544-558.