The nematodes of the genus Dicelis Dujardin, 1845 parasitic in earthworms: the interrelationships of four Eurasian populations

In order to study the phylogenetics and morphology of the genus Dicelis, we collected infected lumbricid hosts from geographically remote areas. Four species of Dicelis were found: A rubidi, D. lovatiana and two new species, D. caledoniensis and D. ussuriensis sp. n. described herein. Dicelis caledoniensis sp. n. is characterised by having pocket-like amphids, a nearly cylindrical pharynx, distinct excretory pore and duct, the ovary extremity located between the vulva and anus, short bristles coating the egg-shell, fimbriate organs being located at mid-tail in females and at one-third of the tail in males, broad, scarcely tapered tail of both sexes ending in a rounded tip and distinctly cephalated spicules with pointed distal tips. Dicelis ussuriensis sp. n. is characterised by pore-like amphids, pharynx with slightly expanded basal part and conical posterior, indistinct excretory pore, the ovary extremity located between the Vulva and anus, egg-shells with high tubercles, fimbriate organs located mid-tail, the conical tail of both sexes with bifurcate tail tip, and the long thin spicules with elongated angular manubria. Partial sequences of the 18S and 28S rDNA were obtained for all four species and Subjected to maximum parsimony (NIP), maximum likelihood (ML) and Bayesian analysis. All three methods of analysis showed that the genus Dicelis is closely related to the free-living nematode genera Zeldia and Cephalobus. Both morphological and molecular data showed the four species comprised two closely related species pairs with D. lovatiana Ivanova, 1993 resembling A caledoniensis sp. it. and D. rubidi Ivanova, 1994 resembling D. ussuriensis sp. n. A new host for D. rubidi Ivanova, 1994 is recorded.