Levipalatum texanum n. gen., n. sp. (Nematoda: Diplogastridae), an androdioecious species from the south-eastern USA

Abstract

A new species of diplogastrid nematode, Levipalatum texanum n. gen., n. sp., was isolated from scarab beetles (Coleoptera: Scarabaeidae) in Texas and baited from soil in Virginia, USA. Levipalatum n. gen. is circumscribed by stomatal and pharyngeal morphology, namely a long, hooked dorsal tooth connected to a ‘palate’ projecting anteriad and mediad, subventral telostegostomatal ridges of denticles, and the dorsal radius of the pharynx bulging anteriad. The males of the new species are distinguished from most other Diplogastridae by the frequent presence of ten pairs of genital papillae. Phylogenetic relationships inferred from 11 ribosomal protein-coding genes and a fragment of the small subunit rRNA gene strongly support L. texanum n. gen., n. sp. to be a sister group to Rhabditolaimus, which lacks all the stegostomatal and pharyngeal characters diagnosing the new genus. The new species expands comparative studies of the radiation of feeding morphology that are anchored on the model organism Pristionchus pacificus. The phylogenetic position of L. texanum n. gen., n. sp. indicates a new case of convergent evolution of hermaphroditism in Diplogastridae.