An unusual occurrence of Thorea hispida (Thore) Desvaux chantransia on rusty crayfish in West Central Ohio

The occurrence of Thorea hispida (Thore) Desvaux in west-central Ohio represents a new North American record and the first recorded occurrence of an epizooic chantransia stage. The chantransia of T. hispida was attached to the crayfish Orconectes rusticus Girard via multicellular holdfasts on the antennae and antennules and within the grooves, joints, and sensory setae pockets of the dorsal carapace surface. Tufts of filaments bearing morphology resembling the form taxon, Chantransia pygmaea, grew from the holdfast. Chantransia percent cover was positively correlated to carapace size, with larger individuals having greater coverage. This size relationship may be due to less frequent molts by larger individuals. The chantransia of T. hispida was noted growing almost exclusively on an O. rusticus population within a stream reach and was only present microscopically on rocks during a short period in the spring. This report of T. hispida is also a new northern temperate locality in North America for a taxon that has typically been observed only in more tropical and subtropical locations.