Description of Ruehmaphelenchus juliae n. sp. (Tylenchina: Aphelenchoididae) isolated from an ambrosia beetle, Xylosandrus crassiusculus (Motschulsky), from South Florida

Abstract

During a survey of nematode associates of ambrosia beetles from dead and dying red bay and avocado trees affected by the laurel wilt epidemic in southern Florida, a Ruehmaphelenchus species was isolated from the non-native ambrosia beetle, Xylosandrus crassiusculus. The new species is characterised by its possession of an oral disc at the stoma opening, three lines in the lateral field, male spicule with clear dorsal and ventral limbs connected by elongated triangular cuticle, thin membrane-like tissue and cuticular bridge-like structure, conical tail with pointed tip of males and conical tail with digitate mucro of females. The new species is very similar to four previously described species: R. asiaticus, R. digitulus, R. thailandae and R. sirisus, and can be distinguished only by some minor morphological differences in male tail characters, i.e., spicule morphology, position of genital papillae and tail tip shape, and morphometric values. However, the new species is phylogenetically unique, i.e., it is the basal taxon of the Ruehmaphelenchus clade and close to Bursaphelenchus spp. Ruehmaphelenchus juliae n. sp. is therefore proposed based on its morphological diagnostic characters and molecular sequences of near-full-length of SSU, internal transcribed spacer region, D1, D2 and D3 expansion segments of LSU ribosomal RNA and partial mitochondrial COI genes.