Morphological and molecular characterization of Isobinema luisdearmasi sp. nov. (Oxyuridomorpha: Thelastomatoidea: Travassosinematidae) from the mole cricket Gryllotalpa orientalis Burmeister, 1838 (Orthoptera: Gryllotalpidae) in Japan

Isobinema luisdearmasi sp. nov. (Nematoda: Oxyuridomorpha: Travassosinematidae) is described from the mole cricket Gryllotalpa orientalis Burmeister, 1838 (Orthoptera: Gryllotalpidae) in Kasugai, Aichi Prefecture, Japan. The females of I. luisdearmasi sp. nov. are similar to I. flagellocercum Rao, 1958 (type species of the genus) by some morphometric variables overlapping in both species, namely the body length and the comparative length of the oesophagus and tail.

The new species can be differentiated from I. flagellocercum by its comparatively slender body and larger eggs. Isobinema luisdearmasi sp. nov. lacks lateral alae, which are present in I. flagellocercum. The new species differs from I. indicum Singh & Singh, 1990 by its slightly longer body, comparatively shorter oesophagus and tail, and more posterior vulva.

Isobinema jairajpurii Singh & Malti, 2003 is larger than I. luisdearmasi sp. nov.; its body is more robust, and its oesophagus and tail are comparatively shorter. Isobinema neoflagellocercum Padmaja & Lakshmi, 1994 differs from I. luisdearmasi sp. nov. by its more anterior vulva. The nomenclature of the species of Isobinema as well as Binema ornata Travassos, 1925, was corrected in order to match the gender of generic and specific epithets.

Additionally, the genus Hindustanicola Morffe & García, 2023, is considered a junior synonym of Hexasinghiella Ceccolini & Cianferoni, 2021. Isobinema dimorphicaudum Parveen & Jairajpuri, 1982 is proposed as species inquirenda, since the identity of the species cannot be reliably determined. The phylogeny of I. luisdearmasi sp. nov. is inferred by the D2-D3 domains of the 28S rDNA, the 18S rDNA, and the mitochondrial COI.

For all three markers, the new species was recovered in a clade with other taxa from mole crickets. In the case of the COI, the only marker with an available sequence of I. flagellocercum, both species form a monophyletic clade.