Redescription of Dichelyne (Cucullanellus) jialaris (Nematoda: Cucullanidae), a parasite of seabreams (Perciformes: Sparidae) in East Asia.

An insufficiently known nematode species Dichelyne (Cucullanellus) jialaris Luo, Guo, Fang et Huang, 2004 (Cucullanidae), originally described from the red seabream Pagrus major (Temminck et Schlegel) (Sparidae) in the Taiwan Strait, off China, is redescribed based on light and scanning electron microscopical (SEM) examinations of specimens collected from the intestine of three species of sparid fishes, Acanthopagrus schlegelii (Bleeker), Evynnis tumifrons (Temminck et Schlegel) and P. major, in Hiroshima Bay, Japan. The present redescription provides exact data on the cephalic structure, character of cephalic papillae and amphids, location of the excretory pore, deirids and phasmids, and the number and distribution of caudal papillae in the male; the presence of the dorsal postdeirid in this species is reported for the first time. The SEM study revealed that the anterior cloacal lip has a median lobe-like elevation bearing two minute papillae, whereas the posterior cloacal lip is somewhat depressed, with a median longitudinal rod-like elevation probably serving to direct the movement of spicules. The size of eggs is reported for the first time. Dichelyne (C.) jialaris differs from the morphologically similar D. (C.) pleuronectidis (Yamaguti, 1935) mainly in the shape of the oesophagus. The present finding of D. (C.) jialaris represents the first record of this nematode from fishes in Japanese waters and A. schlegelii and E. tumifrons are its new host records.