Four new species of Steinemema Travassos, with short infective juveniles from Vietnam

摘要

The length of the infective juveniles (Us) of four new species (Steinemema cumgarense sp. n., Steinemema eapokense sp n., Steinemema backanense sp n and Steinemema sasonense sp. n.) is less than 600 mu m. The I.J have lateral fields with four centralridges and two prominent marginal ridges (at least in anterior body half). As the Us have no horn-like appendages on the cephalic end, these species belong to the 'carpocapsae-scaterisci-tami' group. The length of IJ of S. cumgarense sp. n. is similar toS. eapokense sp n. and S siamkayai, but differs from S. sasonense sp. n., S. carpocapsae, S. scapterisci and S. tami. This species can be distinguished from the closely related species S. eapokense sp. n, by the D% value, and the hyaline part of I.J tail Steinemema cumgarense sp n Us have thicker body than S. siamkayai. The spicules and gubemaculums of this species are longer than S, backanense sp. n. Moreover, S. cumgarense sp n. differs from S. sasonense sp n. in IJ pharynx and tail length. The E% value of S. eapokense sp n helps to distinguish this species from S siamkayai Us of S. eapokense sp n. are shorter than those of S. sasonense sp. n.., S. carpocapsae and S. scapterisci. The spicule of S. eapokense sp. n. is shorter than that in S. backanense sp n. Males of S. backanense sp. n can be distinguished from S. cumgarense sp. n., S. eapokense sp. n, and S. sasonense sp. n., and also from S. tami, S. scapterisci and S,, siamkayai by their short spicules Steinemema backanense sp. n. also differs from S. carpocapsae in D% value of IJs. Steinemema sasonense sp n. can be distinguished from S. scapterisci by the IJ length; and from S. cumgarense sp, n. and S. eapokense sp. n. by longer Us. Steinemema sasonense sp, n. can be distinguished from S. carpocapsae by the shorter pharynx length and D% value of Us. In addition, four new species can be differentiated further from each other and from closely related species of the 'carpocapsae-scaterisci-tami' group by characteristic sequences of their ITS-rRNA gene. The phylogenetic relationships within clade 'carpocapsae-scaterisci-tami' of the genus Steinemema with inclusion of newly sequenced S. cumgarense sp n., S. eapokense sp. n., S. backanense sp. n. and S. sasonense sp. n. are presented on the basisof ITS-rRNA gene sequence analysis.