Morphological and molecular characterisation of Paralongidorus plesioepimikis n. sp. (Nematoda: Longidoridae) from southern Spain

Abstract

Paralongidorus plesioepimikis n. sp. is described and illustrated by light microscopy, scanning electron microscopy and molecular studies from specimens collected in a sandy soil in the rhizosphere of stone pine (Pinus pinea) in Bonares (Huelva Province), southern Spain. The new species is characterised by a very long body (9.71-14.11 mm), an expanded and rounded lip region, with a clear constriction followed by a depression posterior to the amphidial aperture, a very long and flexible odontostyle (202-227 μm), guiding ring located at 36.5-44.0 μm from anterior end, dorsal pharyngeal gland nucleus in anterior part of bulb, one subventral pair of nuclei near middle of bulb, vulva at 33-38%, and a dorsally convex tail with rounded terminus (32-39 μm long). SEM observations showed a very large amphidial fovea with conspicuous aperture ca three-fourths as wide as lip region and cephalic papillae appearing as small apertures, each located just anterior to a distinct cephalic lobe. The sequences of the D2-D3 expansion segments of 28S rRNA, partial 18S rRNA and ITS rRNA gene for P. plesioepimikis n. sp. were obtained. Phylogenetic analyses of P. plesioepimikis n. sp. rRNA gene sequences and of Paralongidorus spp. and Longidorus spp. sequences published in GenBank were done using Maximum Likelihood and Bayesian inference. Paralongidorus species (including P. plesioepimikis n. sp.) clustered together, except for P. bikanerensis which clustered within Longidorus spp. and was clearly separated from all other Paralongidorus spp. in trees generated from the D2-D3 expansion segments of 28S and partial 18S data set. ML analysis using SH-test for the validity of Paralongidorus was performed and showed the validity of the genus using the D2-D3 expansion segment of 28S and partial 18S.