SummaryA new species of a predator aphelenchoidid,Seinura cavernan. sp., is described and illustrated. The new species was isolated from bat guano collected from a calcareous cave in Japan. The new species is characterised by its three-lined lateral field, secretory-excretory pore at the level of the posterior two-thirds of the metacorpus, a long post-uterine sac, hermaphrodite tail shape elongate conoid with a filiform tip, and an androdioecious reproductive mode. The new species is typologically and biologically close toS. steineri, but is distinguished by its longer post-uterine sac, slightly longer stylet and slightly larger median bulb. The comparisons with other morphologically similar species,i.e.,S. chertkovi,S. tenuicaudataandS. steineri, are discussed. A molecular phylogenetic analysis based on two small and large subunit ribosomal RNA genes revealed that the new species is located at the basal position of clade 3 of the Aphelenchoididae, clearly separate fromS. demani, its congener with unclear rectum and anus, which is located at the derived position, suggesting that further generic revision is necessary for the genus.Aphelenchoides liin. comb. (=Seinura lii) is proposed.

SummaryLitylenchus crenatae n. sp., isolated from leaf galls of Fagus crenata from Japan, is described and figured. The new species is characterised by its dimorphism in adult females, six (or more) lateral lines, a more or less pointed tail tip in both sexes, male bursa arising posteriorly and reaching to near tail tip, presence of a quadricolumella and a post-uterine sac in females. Litylenchus crenatae n. sp. is distinguished from its only congener, L. coprosma, by the number of lateral lines, six or more vs four; the lip morphology, offset with very shallow constriction or dome-shaped without clear constriction vs clearly offset; tail tip morphology, more or less pointed vs blunt; and structure of the median bulb, weakly muscular with a clear valve vs not muscular with an obscure valve. The molecular phylogenetic analysis confirms that the new species is close to, but clearly different from, L. coprosma.

Using transmission electron microscopy, we examined the body cuticle ultrastructures of phoretic and parasitic stages of the parasitaphelenchid nematodes Bursaphelenchus xylophilus, B. conicaudatus, B. luxuriosae, B. rainulfi; an unidentified Bursaphelenchus species, and an unidentified Parasitaphelenchus species. Nematode body cuticles usually consist of three zones, a cortical zone, a median zone, and a basal zone. The phoretic stages of Bursaphelenchus spp., isolated from the tracheal systems of longhorn beetles or the elytra of bark beetles, have a thick and radially striated basal zone. In contrast, the parasitic stage of Parasitaphelenchus sp., isolated from bark beetle hemocoel, has no radial striations in the basal zone. This difference probably reflects the peculiar ecological characteristics of the phoretic stage. A well-developed basal radially striated zone, composed of very closely linked proteins, is the zone closest to the body wall muscle. Therefore, the striation is necessary for the phoretic species to be able to seek, enter, and depart from host/carrier insects, but is not essential for internal parasites in parasitaphelenchid nematodes. Phylogenetic relationships inferred from near-full-length small subunit ribosomal RNA sequences suggest that the cuticle structures of parasitic species have apomorphic characters, e.g., lack of striation in the basal zone, concurrent with the evolution of insect parasitism from a phoretic life history.