Description of Lelenchus brevislitus n. sp. (Nematoda: Tylenchidae), an example of a cryptic species from Iran and its phylogenetic relationships with other species in the family

Abstract

Lelenchus brevislitusn. sp. is described and illustrated based on morphological, morphometric and molecular data. The new species is characterised by having females with slender, 452-488 μm long, body lateral field vestigial as a plain simple band under scanning electron microscopy (SEM) in vulval region and absent in proximal and distal body ends, cephalic region short,ca2 μm high, conical and truncate in anterior end in lateral view under SEM, dorso-ventrally flattened, amphidial pouches pocket-shaped and large under light microscopy (LM), their apertures short (ca1 μm long in SEM) longitudinal sinuous slits remarkably wide near the small oral disc and significantly narrowing posteriad stylet, slender. 6.5-8.0 μm long, developed median bulb with distinct valvular plates, monodelphic-prodelphic reproductive system having a short post-vulval uterine sac (PUS), transverse vulval slit (V = 47.5-51.7) bearing small lateral membranes on each side, long filiform female tail (154-170 μm, c = 2.8-3.1, c′ = 21.5-28.3), and males unknown. The new species is considered to be a cryptic species inside the Tylenchidae. Morphological comparisons with all species of the genus are discussed. Phylogenetic studies were performed for further characterisation of the new species, and the results, using nearly full length 18S rDNA data, revealed it formed a clade with an isolate ofL. leptosoma, both of which are in a sister clade with an isolate ofSakia. In a reconstructed phylogenetic tree using partial 28S rDNA sequences, the new species formed a monophyletic group, again withL. leptosoma, a sister clade to someMalenchusspp.