The ultrastructural morphology of the buccal capsule and intestine (mid-gut) of the predatory marine nematode Sphaerolaimus balticus is investigated. The major part of the voluminous barrel-shaped buccal capsule is made up of strongly modified somatic cuticle and hence presents itself as an intricately differentiated cheilostome. The latter consists of three compartments: i.e., i) labial region; ii) striated region with six rows of fine longitudinal ribs; and iii) shagreen band penetrated by about ten projections of arcade tissue. The gymnostome and telostome are narrow and together constitute a small posterior portion of the buccal capsule. The mouth is evidently opened by contraction of anterior longitudinal somatic muscles. The intestine is characterised by a very thin and homogenous basal lamina. The cytoplasm of the enterocytes contains lipid granules, large electron-light vacuoles and rounded concentric inclusions in membranous vacuoles. Apical microvilli are separated from the lumen by a dense three-layered glycocalyx resembling the peritrophic membrane in the intestine of arthropods. The glycocalyx is only a supportive structure of the mid-gut. The most peculiar features of the intestine are the particularly strong junctions connecting the glycocalyx with the cells. The junctions appear as cytoplasmic bundles attached to the dense glycocalyx layer by dint of hemidesmosomes.
Bursaphelenchus acaloleptae n. sp. is described and figured based upon its morphological characters and molecular profiles. The new species belongs to the xylophilus-group of the genus and is typologically characterised by its secretory-excretory pore being located slightly posterior to the median bulb, weakly tapering, relatively broad and straight female tail with variously shaped terminus, and rounded male bursal flap with squared terminus. The new species is phylogenetically and biologically closest to B. luxuriosae. These cryptic species share the host (habitat) tree species, Aralia elata (Araliaceae), the same carrier insect species, Acalolepta luxuriosa (Cerambycidae), and a characteristic phoretic adult form. However, the new species is typologically distinguished from all other xylophilus-group species by the combination of the above-mentioned characters and molecular profiles (SSU and LSU molecular barcodes). Further, B. acaloleptae n. sp. can be distinguished from its closest relative, B. luxuriosae, by mating experiments, i.e., these two species did not produce a viable F1 generation in reciprocal crossings, thereby confirming separate species status using the biological species concept.
Two new species and a new subspecies of Bursaphelenchus are described. Bursaphelenchus carpini n. sp. and B. cryphali okhotskensis n. subsp. were isolated from Cryphalus carpini emerged from a dead log of a Carpinus sp. collected in Ibaraki Prefecture, Japan, and from C. piceae emerged from a dead log of Abies sachalinensis collected in Hokkaido, Japan, respectively. Meanwhile, B. laciniatae n. sp. was isolated from the bark of dead Ulmus laciniata, which harboured Scolytus esuriens galleries, collected in Hokkaido, Japan. These three species phylogenetically belong to the eggersi/eremus-group clade and share common typological characters such as a relatively slender body, three-lined lateral field, male spicule with a well-developed condylus, short and wide blade (calomus-lamina complex) and lack of clear cucullus. These three species and subspecies can be distinguished from one another and their close relatives by the condylus shape, female tail shape and phylogenetic and biological characters.
Based on earlier investigations, Bursaphelenchus sexdentati sensu lato consists of two distinct forms, a central European and a southern European type. In this paper we recognise these forms at species level and propose B. dietrichi sp. n. for the southern European type, regarding it as distinct from B. sexdentati sensu stricto. The relatively long (733-881 μm) and slender (a = 34.7-43.3) females of the new species have a small vulval flap, a long post-uterine sac extending for 46.6-75.3% of the vulva to anus distance, and a mostly conical tail with a more or less bluntly rounded terminus. The male spicules are strongly ventrally arcuate, measuring 13-17 μm along the arc, and have a bluntly pointed rostrum ca 2-3 μm long in the proximal part and a small cucullus at their distal end. The capitulum is slightly concave and the condylus is ca 2-3 μm long, truncated and slightly hooked. The oval bursa and the disposition of the male caudal papillae, as well as the presence of four lateral lines, justify the assignment of this taxon to the sexdentati-group. Bursaphelenchus dietrichi sp. n. can be distinguished from B. sexdentati s.s. and other related species by morphological characters and sequencing results. Bursaphelenchus sexdentati s.s. is also recorded from China for the first time.
Bursaphelenchus michalskii sp. n. is described from the bark of the European white elm, Ulmus laevis. All propagative stages of the nematode were found in larval galleries of the large elm bark beetle, Scolytus scolytus, and in overlapping gallery systems of this species and the small European elm bark beetle, S. multistriatus. Dauer juveniles of the new nematode are transmitted to new breeding trees under elytra of adult S. scolytus. Bursaphelenchus michalskii sp. n. is characterised by the female body length of 953 (838-1108) μm and male body length of 893 (811-971) μm, very slender body (a = 53.9 (46.1-58.5) and 60.9 (52.2-72.0) in female and male, respectively), lateral fields with three incisures (two bands), excretory pore usually located anterior to the median bulb, lack of vulval flap, long post-uterine sac, relatively small spicules 12.3 (10.8-13.3) μm long with no cucullus and with distinct, somewhat thorn-like, dorsally bent or reflexed condylus and a conical or digitate rostrum, and the arrangement of the seven male caudal papillae (i.e., a single precloacal ventromedian papilla (P1), one pair of adcloacal ventrosublateral papillae (P2) at or just anterior to cloacal slit, one ventrosublateral, postcloacal pair (P3) located at ca 60% of the tail length, posterior to cloacal slit, and one pair (P4) of ventrosublateral papillae located near the base of the bursa). The newly described species shares most of the key morphological characters with members of the eremus-group (sensu Braasch et al., 2009). However, B. michalskii sp. n. is unique amongst Bursaphelenchus species by a combination of female tail and spicule shape, excretory pore position, and other morphometric characters. These findings were confirmed by DNA sequencing and phylogenetic analysis of the 18S and 28S rDNA regions and by the unique molecular profile of the ITS region (ITS-RFLP).
Bursaphelenchus pterocarpi n. sp. isolated from Pterocarpus sp. logs imported from Ghana to Ningbo, China, is described and illustrated. The new species is characterised by a female body length of 630-946 μm, lateral field with four lines, a short 12.6-13.9 μm long stylet with small basal swellings, excretory pore located posterior to nerve ring, outstretched reproductive system with amoeboid sperm inside the spermatheca, a well-developed vulval flap, tail conical and straight with a 1.9-4.8 μm long mucron at the tip, and lacking males in both the wild type and fungal-cultured populations. In a concatenated tree, reconstructed on the basis of the partial 18S, full length ITS and partial 28S rDNA D2-D3 sequences, the new species occupied a basal placement to the clade of xylophilus-group and africanus-group species.
Populations of Hemicriconemoides chitwoodi, H. fujianensis, H. parasinensis, and Criconemoides myungsugae isolated in China from the rhizosphere soil of woody perennials were characterised molecularly, important morphological details being elucidated by SEM observations. The morphometric data of the Chinese populations were compared with all previously reported populations. The SEM observations of en face views indicated that H. chitwoodi and H. parasinensis have lip patterns belonging to type 1 and phylogenetically both species clustered with other Hemicriconemoides species that showed the same kind of lip pattern. On the other hand, H. fujianensis showed a lip pattern belonging to type 2 and phylogenetically appears basal to the above-mentioned clade. SEM observation of C. myungsugae showed that the first lip annulus forms a non-projecting uninterrupted disc and the labial annulus is a rectangular shape with slight dorsal and ventral indentations. Phylogenetic relationships among Criconemoides spp. are apparently not well resolved. The present study provides updated morphological descriptions, molecular diagnostics and phylogenetic relationships of H. chitwoodi, H. fujianensis, H. parasinensis, and C. myungsugae, the last species being the first report from China.
The host response to Meloidogyne javanica infection of selected Oryza sativa and NERICA (New Rice for Africa) genotypes that are commonly grown in Tanzania and East Africa was examined. The O. sativa genotypes ‘Komboka’ and ‘Supa’ appeared to be partially resistant. A further experiment showed that both genotypes are also partially resistant to M. graminicola infection. The host response of ‘Komboka’ and ‘Supa’ to M. javanica and M. graminicola was further examined and compared in indoor growth chamber conditions. The genotypes ‘TOG5674’, ‘TOG5675’, ‘CG11’ and ‘CG14’ (both O. glaberrima) were included as the resistant reference genotypes for M. graminicola and the genotype ‘UPLRi-5’ (O. sativa) was included as the susceptible reference genotype for both species of root-knot nematodes. Meloidogyne graminicola was more aggressive on ‘Komboka’ and ‘Supa’ than M. javanica. Significantly less root galling was observed on ‘Komboka’ and ‘Supa’ than on ‘UPLRi-5’. In ‘Komboka’ and ‘Supa’ significantly fewer second-stage juveniles (J2) were able to penetrate the roots, to develop into adult females and to reproduce compared with ‘UPLRi-5’. Differential emigration of J2 from the roots of ‘Komboka’ and ‘Supa’ compared with ‘UPLRi-5’ contributed to the observed partial resistance in these genotypes to M. graminicola and M. javanica. Nematodes that successfully penetrated and developed in ‘Komboka’ and ‘Supa’ showed aberrant phenotypes. ‘Supa’ and ‘Komboka’ may be recommended for use by farmers in M. javanica and M. graminicola-infested fields.