Heterochely is an important feature in some marine decapod crustaceans, but it is seldom investigated in freshwater crayfish. In this study, we applied a biometrical analysis targeting wild populations of three European crayfish species, Astacus leptodactylus, Astacus astacus, and Austropotamobius torrentium, as well as one invasive North American species, Faxonius limosus. Field data were combined with video-recorded observations to understand the usage of chelae in laboratory experiments for A. leptodactylus and F. limosus. According to biometrical measurements, heterochely was evenly distributed between species and sexes in wild populations, leading to the assumption that there is no specific pattern in chela size. Moreover, we found that the ambidextrous usage of chelae is a commonly encountered behaviour in crayfish, since no significant relationship was found between their chelae and asymmetry. This behaviour could maximize the chances of survival for crayfish in general, since losing one or both chelae is often recorded in the wild.
Laimaphelenchus spiflatus n. sp. isolated from declining Chinese pine, Pinus tabuliformis, is described and illustrated. The new species can be characterised by its relatively long body size of 1150 ± 108 (976-1437) μm for females and 1092 ± 78.6 (905-1235) μm for males, lateral field with four lines, females with a long vulval flap, and tail conoid, slightly ventrally curved and ending in a stalk having 8-12 projections when observed with SEM. Males are common, with 27.3 (23.4-28.8) μm long spicules having blunt (not well-developed) condylus and rostrum and truncate simple distal tip, and four caudal papillae. By having a vulval flap, four lateral lines and tail end with a stalk (without four tubercles), the new species comes close to L. preissii, L. simlaensis, and L. unituberculus, but can be differentiated from them by morphological characters and morphometric data. In phylogenetic analyses using near full length 18S and D2-D3 expansion segments of 28S rDNA, Laimaphelenchus spiflatus n. sp. appeared as an independent lineage separated from the other Laimaphelenchus spp. that are currently sequenced for their aforementioned genomic regions.
Cryptaphelenchus paravaricaudatus n. sp., from declining Pinus massoniana in China, is described and illustrated. The new species is characterised by the 233-308 μm long females with distinctly annulated cuticle, lateral fields with four lines, lip region separated from the body by a shallow depression, delicate stylet with small knobs, post-vulval uterine sac short and rectum and anus invisible. Males are 204-259 μm long, with spicules 8.5-12.0 μm long, condylus well developed and broad, caudal papillae arranged as a single (P1) and a pair of precloacal papillae (P2) plus two pairs of postcloacal papillae (P3 and P4). Based upon the general morphology of the female, the new species most closely resembles C. varicaudatus. The morphological differences with the aforementioned species and other species having similar morphology are discussed. The phylogenetic analyses based on small (SSU) and large subunit (LSU) D2-D3 expansion segments of ribosomal DNA (rDNA) of different individuals of the new species revealed that it fell into the clade of Cryptaphelenchus in both SSU and LSU trees. The monophyly of the genus was retained.
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 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.