Description of Ruehmaphelenchus kuroshioi n. sp. and R. interjectus n. sp. (Tylenchomorpha: Aphelenchoididae) isolated from ambrosia beetles, Euwallacea spp. (Scolytinae), from Japan

Abstract

Summary Two Ruehmaphelenchus species were isolated from the ambrosia beetles Euwallacea kuroshio and E. interjectus, collected from Okinawa and Kagoshima, Japan, respectively. Both nematodes were successfully cultured on a lawn of the grey mould Botrytis cinerea. Morphological observation and molecular characterisation revealed that both species are undescribed; therefore, the nematodes are described herein as R. kuroshioi n. sp. and R. interjectus n. sp. Phylogenetically, both species are closely related to R. formosanus, R. fujiensis, R. digitulus and R. asiaticus. Ruehmaphelenchus kuroshioi n. sp. is characterised by a conical male and female tail, which has a terminal projection (mucron), small male spicule with a weakly-developed triangular condylus, dorsal and ventral limbs that are connected to each other by three different tissues, and clearly separated distal pairs of genital papillae (P3 and P4). However, R. kuroshioi n. sp. can be distinguished from its close relatives by a combination of male and female tail characters and its distinctive phylogenetic status. Ruehmaphelenchus interjectus n. sp. is almost identical to R. formosanus, sharing characteristic lateral spikes of the spicule; they form a well-supported phylogenetic clade. However, R. interjectus n. sp. is distinguished from R. formosanus by morphometric values and ribosomal RNA, i.e., a 6-bp difference from the ca 1.7 kb molecular sequence of the 18S ribosomal RNA of R. formosanus, which warrants independent species status.