Rhabdochona rotundicaudatum n.sp. and a redescription of R. cascadilla Wigdor, 1918 (Nematoda: Thelazioidea) from minnows in southern Ontario, Canada

Abstract

Rhabdochona rotundicaudatum n.sp. is described from hornyhead chub (Nocomis biguttatus (Kirtland, 1841)), and a redescription of R. cascadilla Wigdor, 1918 from common shiner (Notropis cornutus Mitchill, 1817) is provided. Rhabdochona rotundicaudatum n.sp. most closely resembles Rhabdochona cascadilla, but is distinguished by the size and form of the right spicule and the form of the tail in both sexes. Rhabdochona rotundicaudatum n.sp. has a rounded tail tip whereas R. cascadilla has a pointed tail tip. Females of both species produce ovoidal eggs without filaments or floats. No other Rhabdochona species from North America have both a rounded tail tip and smooth eggs. Adult R. rotundicaudatum n.sp. were also recovered from a mayfly (Ephemeroptera). The occurrence of an adult spirurid nematode in an invertebrate is rare; adult spirurids are normally found only in vertebrate (definitive) hosts.