Morphological and Molecular Characterisation of Myxidium kudoi Meglitsch, 1937 from the Blue Catfish Ictalurus furcatus, Valenciennes in Oklahoma, USA

Abstract

Myxidium kudoi Meglitsch, 1937 has been described from the type host, blue catfish Ictalurus furcatus, with no additional host records or molecular data available for this species. To provide molecular data and a novel host locality for this species and carry out phylogenetic analyses to infer the evolutionary relationship of the species to other members of the family Myxidiidae for which DNA sequence data is available. These data were collected using myxospores from the gallbladder of a blue catfish, Ictalurus furcatus collected from Lake Texoma, Oklahoma, USA. Myxospores were morphologically consistent with the only other account of this species and not any other Myxidium species described from siluriform fishes. Myxospores were oblong with rounded ends and were 10.8-12.6 (11.6 ± 0.5) µm in length and 4.7-6.6 (5.7 ± 0.5) µm in width. Polar capsules were subspherical and 2.7-3.9 (3.4 ± 0.3) µm in length and 2.4-3.5 (3.1 ± 0.3) µm in diameter, with each capsule containing a polar filament with 3-4 coils. Molecular data consisted of a 2918-bp sequence of the partial 18S, complete ITS1, 5.8S, ITS2, and partial 28S ribosomal rRNA regions as well as a 2455-bp sequence of partial 28S ribosomal RNA. The partial 18S and 28S data was used in a concatenated Bayesian phylogenetic analysis to further infer the evolutionary relationships of the Myxidiidae. Additionally, the partial 18S data was used in a separate phylogenetic analysis. The present work reports novel morphological and molecular data for Myxidium kudoi as well as a novel locality of occurrence for this species. In concatenated phylogenetic analysis using 18S and 28S data and other molecular data from Myxozoa, M. kudoi grouped with other freshwater Myxidiidae. In the single-locus, 18S analysis, M. kudoi grouped with Myxidium rhodei from Rutilus rutilus and Myxidium amazonense from Corydoras melini, the only other Myxidium species of catfish for which molecular data are available.