Research Article

Molecular and ultrastructural characterization of Dictyocoela diporeiae n. sp. (Microsporidia), a parasite of Diporeia spp. (Amphipoda, Gammaridea)

Caractérisation moléculaire et ultrastructurale de Dictyocoela diporeiae n. sp. (Microsporidia), un parasite de Diporeia spp. (Amphipoda, Gammaridea)

¹ Department of Fisheries and Wildlife, Michigan State University, 1129 Farm Lane, 177K Food Safety and Toxicology Building, East Lansing, Michigan 48824, USA
² Department of Pathobiology and Diagnostic Investigation, Michigan State University, 1129 Farm Lane, 174 Food Safety and Toxicology Building, East Lansing, Michigan 48824, USA

^* Corresponding author: faisal@cvm.msu.edu

Received: 28 February 2014
Accepted: 3 June 2014

Abstract

Dictyocoela diporeiae n. sp. is described from Diporeia spp. (Amphipoda, Gammaridea) collected from Lake Superior (USA), and its morphology and taxonomic affiliation are discussed. In hematoxylin- and eosin-stained sections of infected amphipods, the microsporidian was observed to infect muscle tissue surrounding the ovaries. Melanized hemocytic encapsulations were often observed in or near masses of microsporidians. The microsporidians appeared as spores measuring 1.99 ± 0.09 μm long by 1.19 ± 0.05 μm wide. Each spore contained eight coils of isofilar polar filaments that were arranged in single ranks. Polar filaments measured 71 ± 3 nm in diameter. A prominent lamellar polaroplast composed of ordered concentric membranes was found at the apical end of the spore surrounding the polar filament. A distinct posterior vacuole was observed at the distal end of the spore. Phylogenetic analysis based on 16s RNA sequences showed that the microsporidian belongs to the genus Dictyocoela, and is most similar to D. berillonum, yet distinctly different. The species is new, based on its morphology, genetic sequence, host, and location within the host.

Résumé

Dictyocoela diporeiae n. sp. est décrit de Diporeia spp. (Amphipoda, Gammaridea) prélevé dans le Lac Supérieur (USA), et sa morphologie et affiliation taxonomique sont discutées. Dans les coupes d'amphipodes infectés colorées à l'hématoxyline-éosine, il a été observé que la microsporidie infecte les tissus musculaires entourant les ovaires. Des encapsulations hémocytiques mélanisées ont été souvent observées dans les masses de microsporidies ou à proximité. La microsporidie est apparue sous forme de spores mesurant 1,99 ± 0,09 µm de long et 1,19 ± 0,05 μm de large. Chaque spore contenait huit spires de filaments polaires isofilaires disposés en rangs simples. Les filaments polaires mesuraient 71 ± 3 nm de diamètre. Un polaroplaste lamellaire important, composée de membranes concentriques ordonnées, a été trouvé à l'extrémité apicale de la spore et entoure le filament polaire. Une vacuole postérieure distincte a été observée à l'extrémité distale de la spore. L'analyse phylogénétique basée sur les séquences d'ARN 16S a montré que la microsporidie appartient au genre Dictyocoela, et est très semblable à D. berillonum, tout en s’en démarquant. L'espèce est nouvelle de par sa morphologie, séquence génétique, hôte, et localisation dans l'hôte.