Transmission electron microscopic observation of body cuticle structures of phoretic and parasitic stages of Parasitaphelenchinae nematodes

Abstract

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.

Different predation capacities and mechanisms of Harmonia axyridis (Coleoptera: Coccinellidae) on two morphotypes of pear psylla Cacopsylla chinensis (Hemiptera: Psyllidae)

“…The cuticle thicknesses of the first abdominal segment of the two morphotypes of C . chinensis were compared by using the program ImageJ (https://imagej.nih.gov/ij/) [53]. Five psyllids were measured for each morphotype.…”

Three Seinura species from Japan with a description of S. shigaensis n. sp. (Tylenchomorpha: Aphelenchoididae)

“…The nematode lysate served as the template DNA for polymerase chain reaction analysis. After confirming the species identity within each strain, ca 4.2 kb of the ribosomal RNA region, including the nearly full-length small subunit (SSU), internal transcribed spacer (ITS) including the ITS1, 5.8S and ITS2 regions and the D1-D4 segments of the LSU (D1-D4 LSU), as well as ca 0.7 kb of mitochondrial cytochrome oxidase subunit I (mtCOI) were determined for each strain using the methodology described by Kanzaki and Futai [8] and Ekino et al [9]. The molecular sequences were deposited in GenBank with accession numbers LC596442 (rDNA of NKZ272 = S. caverna), LC596444 (mtCOI of NKZ272 = S. caverna), LC596443 (rDNA of NKZ274 = S. caverna), LC596445 (mtCOI of NKZ274 = S. caverna), LC596440 (rDNA of NKZ276 = S. shigaensis n.…”

Feeding Dimorphism in a Mycophagous Nematode, Bursaphelenchus sinensis

“…aberrans has only been reported from field-collected materials, its species status has not been confirmed with genotyping, and its insect parasitism or feeding behaviour have not been experimentally observed. Also, the parasitic forms of the other two species were recently confirmed as an alternative phoretic form, i.e., a non-feeding transportation survival form 23 . Therefore, the presence/absence of functional feeding dimorphism/polymorphism has not been confirmed yet in non-diplogastrid nematodes.…”