Myxobolus cognati n. sp. (Myxosporea) from the opercular integument of Cottus cognatus (Cottidae) in Lake Michigan.

A myxosporean producing aggregations of white pseudocysts in skin covering the posterior margin of the operculum and perioral tissue of Cottus cognatus in Lake Michigan is described as Myxobolus cognati n. sp. (Myxosporea). Histological sections revealed that the parasite develops in vascularized regions of the dermis and with development protrudes beyond the surrounding skin surface. Fixed spores are oval in front view, measure 12.0-14.0 microns long and 9.5-10.5 microns wide, and contain 8-11 filament coils wound tightly and perpendicular to the longitudinal axis of the capsule. Myxobolus cognati resembles Myxobolus rhinichthidis Fantham, Porter and Richardson, 1939 from subepithelial tissue of the operculum of the cyprinid Rhinichthys cataractae. Spores in the 2 species are the same size and shape. However, in contrast to those of M. cognati, spores of M. rhinichthidis have filament coils wound loosely at 45 degrees to the axis of the polar capsule and have no sutural ridge folds.