Mesenchytraeus megachaetus, a new enchytraeid with enlarged ventral chaetae (Annelida, Clitellata) from Changbaishan Mountain, China

Abstract

Abstract.-Mesenchytraeus megachaetus, new species, is described from northeast China. It is characterized by possessing enlarged ventral chaetae in segments V-VI (3-4 per bundle); nephridia with solid unlobed postseptale, relatively developed interstitial tissue and near-septal origin of the efferent duct; nephridia occurring in 5 pairs in preclitellar region; seminal vesicle absent, replaced by 5-8 naked ''spermatozeugmata'' in dorsal region of XI; spermathecae without diverticula and attached entally to esophagus in segment VI; atria tubular (indistinct from vasa deferentia) and without prostate glands; egg sac much developed (extending to XVII-XVIII).

Mesenchytraeus anisodiverticulus, a new enchytraeid with enlarged ventral chaetae (Annelida, Clitellata) from north-eastern China

“…M. tetrapodus Timm, 1978, another aquatic species, differs from M. anisodiverticulus by having only one enlarged ventral chaeta per bundle, six pairs of nephridia in preclitellar region (five pairs in M. anisodiverticulus), larger seminal vesicle (extending up to VIII), spindle-shaped atria with prostate glands, and elongate spermathecae (extending back to IX-X) (Table II). Shen et al (2011) this study…”

“…Among them, the new species most resembles M. megachaetus Shen et al, 2011 for the chaetal pattern, the position of enlarged ventral chaetae (V-VI), the number of nephridia in the preclitellar region, the presence of sperm bundles, the absence of prostate glands, and the habitat. However, the new species differs from M. megachaetus by possessing larger body size, fewer enlarged ventral chaetae (2 vs. 3-4 per bundle), different patterns of the clitellar granulocytes and hyalocytes, bilobed nephridial postseptale (in M. megachaetus nephridial postseptale are unlobed), seminal vesicle, atrium distinct from vas deferens, and spermathecae with two asymmetrical diverticula.…”

“…Up to now, 10 species and subspecies within this subgroup had been described (5 with enlarged ventral chaetae and 5 with enlarged lateral chaetae), accounting for nearly one-sixth of the recorded Mesenchytraeus taxa (Nielsen & Christensen 1959;Dash 1970;Timm & Popchenko 1978;Piper et al 1982;Timm 1994;Schmelz & Collado 2010;Shen et al 2011).…”

Mesenchytraeus asymmetriauritus,a new enchytraeid (Annelida, Clitellata) from northeastern China

“…During previous investigations, some species new to science and endemic were found there, including three Mesenchytraeus (Shen et al 2011(Shen et al , 2012a. During a further investigation of the enchytraeid fauna there, we identified one new species belonging to Mesenchytraeus.…”

“…Changbai harbors a highly diverse assemblage of enchytraeids, numbering a total of ca. 50 species so far (Chen 2009, Shen 2013, including three species of Mesenchytraeus (Shen et al 2011(Shen et al , 2012a. These taxa had been all collected during summer months.…”