Redescription of Dichelyne (Cucullanellus) cotylophora (Ward &Magath, 1917) (Nematoda: Cucullanidae) parasitic in freshwater fishes of eastern North America

Abstract

Dichelyne (Cucullanellus) cotylophora (Ward &Magath, 1917) Petter, 1974, is redescribed based on specimens from 440 perch (Perca flavescens) collected in Lake Erie, Ontario, from May 10 to October 29, 1982. There is a dorsoventrally elongate mouth opening and enlarged oesophastome with an armature similar to that described for other species of Dichelyne and Cucullanus. Dichelyne cotylophora most closely resembles Dichelyne bullocki Stromberg &Crites, 1972, from which it can be distinguished by possessing a markedly thicker body cuticle and by sexual maturation at a larger body size. Dichelyne cotylophora is reported in P. flavescens from two new localities: St. Lawrence River at Montreal, Québec, and Lake Memphremagog, Eastern Townships, Québec. This species occurs in a wide variety of fishes in eastern North America, but its main host is P. flavescens. A five- to six-fold increase in size and morphological changes occur during growth of adult D. cotylophora. The oesophastome of small worms is relatively undeveloped, especially the processes extending from the oesophastomal ring which are conspicuous in large adult worms. The caudal pseudosucker, which is prominent in large males, is undeveloped in small specimens. Morphometric analysis indicated that measurements of body dimensions can be misleading in taxonomy of cucullanids.