Mesenchytraeus longiductus, Christensen & Dózsa-Farkas, 2012

Christensen, Bent & Dózsa-Farkas, Klára, 2012, A new genus Globulidrilus and three new enchytraeid species (Oligochaeta: Enchytraeidae) from Seoraksan National Park (Korea), Journal of Natural History 46 (45 - 46), pp. 2769-2785 : 2780-2783

publication ID	https://doi.org/ 10.1080/00222933.2012.737038
persistent identifier	https://treatment.plazi.org/id/03E16D7C-FFB7-FFCE-76FB-F6308FB1FA80
treatment provided by	Felipe
scientific name	Mesenchytraeus longiductus
status	sp. nov.

Treatment

Mesenchytraeus longiductus View in CoL sp. nov.

( Figures 7–9 View Figure 7 View Figure 8 View Figure 9 )

Type material

Type Locality. Extracted from moist soil at the type locality.

Holotype. M.5 Slide No 562 (anterior part of the worm opened dorsally)

Paratypes. P. 92.1–5 (Slide No. 559, 564, 578, 579, 580). All worms are adult. On slide 564 the worm was squashed, only the chaetae are visible.

Other material examined. One living specimen, unfortunately damaged after fixation.

Etymology

Named after the very long sperm duct

Description

Medium-sized worm. Colour whitish. Holotype 12.8 mm long, 300 µm wide at VIII and 340 µm at the clitellum (fixed), segments 56. Number of segments of paratypes 48–55. Body length 7.5–15 mm, width about 600 µm at VIII and 750 µm at the clitellum (in vivo), length of fixed specimens 7–8 mm, width 350–600 µm at VIII, 370–670 µm at the clitellum. Chaetae sigmoid with nodulus, 4,5,3,4–4,5:5,3,2,4–5, 6,(7,8). Chaetae generally 50–60 µm long. In V and VI only 2 or 3 chaetae. In the ventral bundles ( Figure 8E View Figure 8 ) they are much larger and stronger (105–110 µm long) whereas the chaetae in the same lateral bundles only 63–80 µm long. From VI is seen a gradual decrease in size backwards to the clitellum in the posterior segments the number of chaetae per bundle increases but without any major change in their dimensions.

Head pore transversal slit on I near the apex dorsally ( Figure 8A View Figure 8 ). Epidermal gland cells regularly scattered ( Figure 8B View Figure 8 ). Clitellum covers XII–XIII, gland cells irregularly arranged. Body wall 20–25 µm thick, cuticle <1µm (fixed), muscle layer is thin. Brain ( Figure 8C View Figure 8 ) incised anteriorly and slightly convex posteriorly, about 100 µm wide and 75 µm long (fixed).

Two primary pharyngeal glands (in 4/5–5/6) not united dorsally and two or three secondary pharyngeal glands (in V–VII); the secondary glands lobed. Chloragocytes 20–25 µm long.

Dorsal blood vessel originates in XVII, the anterior bifurcation in I, blood pale reddish. Five pairs of preclitellar nephridia from 6/7 to 10/11, anteseptale funnel only, postseptale lobed with folded canal, no interstitial tissue, the efferent duct arises between the lobes. Coelomocytes ([ Figure 8D View Figure 8 ] only mucocytes, oval, with granules, light brown, size of cells 14–20 × 9–10 µm (in vivo).

Sperm sac extending backwards to XX–XXI, egg sack to XXIII–XXIV. Sperm funnels ( Figures 5A View Figure 5 and 9A View Figure 9 ) cylindrical, about 250 µm long and 115 µm wide (in vivo), 160 × 70 µm (fixed) collar weakly developed, sperm ducts prominent (width 25–30 µm fixed) and very long, reaching as far as XVI–XVII, irregularly coiled. Before joining the atrium the duct widens into a section with glandular walls (approximately 500 µm long and 38–40 µm wide in vivo and 300 µm long and 40–48 µm wide when fixed). The atrium (80 µm long and 60 µm wide [fixed]) with two very long (200–300 µm) opposing glands ( Figure 7B View Figure 7 ). The atrium connects through a duct (112 µm long and 37 µm wide in vivo 65 µm long 40 µm wide when fixed) to the male copulatory organs surrounded by four to five glands. Bursal slit transversal with bifurcations at the two ends ( Figure 8F View Figure 8 ). No subneural glands. Ectal ducts of spermathecae devoid of glands, length 80–90 µm, diameter 25 µm gradually decreasing ectally, ampullae without diverticula (70–80 µm wide when fixed), ental bulbs projecting into its lumen and sperm in circles around it, ental ducts (150–280 µm long when fixed) join separately but close to oesophagus in VI ( Figures 7C View Figure 7 and 9B–D View Figure 9 ).

Distribution and habitat

Only known from the type locality.

Differential diagnosis

A related species also with enlarged ventral chaetae in some preclitellar segments, attached spermatheca with onion-shaped ampulla devoid of diverticula and an unusually long sperm duct is found in the recently described Mesenchytraeus gigachaetus Shen et al., 2011 ( Shen et al. 2011, Xie 2012). The main difference is the presence of two very large atrial glands in M. longiductus compared with their total absence in M. gigachaetus .