Taxonomy and relationships of a new and the first continental species of Trissonchulus Cobb, 1920 along with two species of Ironus (Nematoda: Ironidae) collected from coal mines.

Abstract

The morphological and taxonomic account of a new and the first terrestrial species of the largely marine genus Trissonchulus Cobb, 1920 is given, along with descriptions of two known species of the sister taxon Ironus Bastian, 1865, reported for the first time from India. Trissonchulus baldwini sp. n. is characterised by the lip region markedly offset from adjoining body by a deep groove; lips strongly amalgamated forming a band or collarette; inner margins of lips serrated; small, setose and backwardly directed cephalic sensilla; narrow funnel-shaped amphids; inconspicuous excretory pore; larger stoma with two dorsal and two ventral outwardly curved, reversible teeth at anterior margins; expanded part 65-70% of the corresponding pharyngeal length; anterior vulva (38-39%); reduced anterior genital branch; long filiform tail and absence of males. The species Trissonchulus lichenii Nasira et Turpeenniemi, 2002 has been placed under genus Syringolaimus de Man, 1888 as S. lichenii on the basis of affinities with the latter. The population of Ironus dentifurcatus Argo et Heyns, 1972 shows slight variations from the original population in having narrower amphids, fang-like projections of the dorsal tooth, conspicuous crystalloids and the presence of caudal pores, while the population of I. terranovus Ebsary, 1985 shows variations from the original specimens in having a smaller body, dome-shaped head and a pair of caudal pores. On morphological grounds, among the congeners T. baldwini sp. n. has been found to show a close relationship with T. acutus and T. benepapillosus while showing many affinities to I. terranovus and I. dentifurcatus on account of morphometric characteristics.