A new genus and two new nematode species (Drilonematoidea: Ungellidae: Synoecneminae) parasitic in two morphs of Drawida ghilarovi Gates, endemic earthworm from the Russian Far East

Abstract

Drasico n. g. is erected to accommodate two new species of nematode, Drasico nemoralis n. sp. and D. paludigenus n. sp., recovered from coelomic cavities of Drawida ghilarovi Gates, endemic earthworms of the Russian Far East. The new genus is characterised by the following unique for the Synoecneminae characters: apical portion of the head attenuated, cephalic hooks displaced to the base of attenuated portion, amphids displaced posterior to cephalic hooks, excretory duct short and weak, males possessing several genital papilliform sensilla. The new species are differentiated by the size, number and disposition of the male genital sensilla (larger and more numerous in D. nemoralis n. sp.); the body shape of females (with thinner neck and wider mid-body in D. paludigenus n. sp.) and the ovarian tube arranged in transversal folds in D. paludigenus (vs longitudinal folds in D. nemoralis n. sp.). Nucleotide sequences of D2-D3 expansion segment of 28S rDNA for the two new species differed at 13 positions. Phylogenetic analysis revealed close relationships of Drasico n. g. with species of Siconema Timm, 1966. The host species was represented by two morphs (blue-grey forest and tar-black meadow-swamp morph) with intraspecific divergence of 16-17% for cytochrome c oxidase subunit 1 (COI) gene, and each host morph was found infected by a different nematode species. A co-infection with the plectid nematode Creagrocercus drawidae Ivanova & Spiridonov, 2011 was recorded together with D. nemoralis n. sp. in the blue-grey forest morph.

Reports of Drawida (Oligochaeta: Moniligastridae) from far East Asia

“…Occurring as a litter species or subsoil geophage in forest soils, meadow-swamp and in peat to depths of 1 m (Ganin, 1023), its cold tolerance is found to be 16 C in worms to 20 C for cocoons (Berman et al, 2010). Nematode parasites are also reported (Ivanova et al, 2014) uniquely for two Drawida ghilarovi morphs supporting the current suggestion of separate species rather than just morphs or ecotypes.…”

Twenty Years after De Ley and Blaxter—How Far Did We Progress in Understanding the Phylogeny of the Phylum Nematoda?

“…Both Osstellidae and Bicirronematidae are represented by a single taxon in published analyses, while the largest family of this infraorder, Cephalobidae, is paraphyletic [ 13 , 60 ]. It also includes Daubayliidae (not included in [ 2 , 3 ]) [ 48 ] and Drilonematomorpha, represented by Drilonematidae and Ungellidae in published phylogenies [ 60 , 61 ]. The remaining families Alirhabditidae and Elaphonematidae from Cephalobomorpha and Homungellidae and Pharyngonematidae from Drilonematomorpha have not been included in molecular phylogenies.…”

The re-description of Synoecnema hirsutum Timm, 1959 (Synoecneminae, Ungellidae, Drilonematoidea) from a pheretimoid earthworm in Vietnam with the analysis of its phylogenetic relationships

“…The family Ungellidae has been split into Synoecneminae accommodating species lacking male spicular apparatus and Ungellinae housing ones with spicules and a gubernaculum . While no molecular data are available for Ungellinae, a limited number of molecular data was obtained for three out of 10 genera of Synoecneminae, namely Synoecnema, Siconema and Drasico Ivanova, Ganin & Spiridonov, 2014. The phylogenetic analysis, based on the D2-D3 region, confirmed the validity of all three genera (Ivanova et al 2014.…”

“…While no molecular data are available for Ungellinae, a limited number of molecular data was obtained for three out of 10 genera of Synoecneminae, namely Synoecnema, Siconema and Drasico Ivanova, Ganin & Spiridonov, 2014. The phylogenetic analysis, based on the D2-D3 region, confirmed the validity of all three genera (Ivanova et al 2014.…”