Decimodrilus diverticulatus, Dózsa-Farkas & Nagy & Felföldi & Hong, 2019

Dózsa-Farkas, Klára, Nagy, Hajnalka, Felföldi, Tamás & Hong, Yong, 2019, Decimodrilus, a new enchytraeid genus from Korea (Annelida, Clitellata, Enchytraeidae), Zootaxa 4661 (2), pp. 385-399 : 387-388

publication ID	https://doi.org/ 10.11646/zootaxa.4661.2.7
publication LSID	lsid:zoobank.org:pub:F13C5EB5-6BDF-43CB-A4E0-598572DDDBA6
persistent identifier	https://treatment.plazi.org/id/F31B87C6-FFCD-8B18-4DD0-FEDEFC055630
treatment provided by	Plazi
scientific name	Decimodrilus diverticulatus
status	sp. nov.

Treatment

Decimodrilus diverticulatus View in CoL sp. n.

( Figs 1 View FIGURE 1 A–B, 2, 3, 6A,C,E–F)

Holotype. NIBRIV0000843108 , slide No. 2575, adult, stained whole mounted specimen.

Type locality. Soil of mixed forest, Mt. Chiaksan, Hakgok-ri, Socho-myeon, Wonju-si, Gangwon-do, South Korea (N 37°23'36.5", E 128°03'15.3"), 395 m asl.

Paratypes. In total 13 specimens, same data as for the holotype. NIBRIV0000843109 , slide No. 2557, NI- BRIV0000843110 , slide No. 2488, P.122.1–122.9, slide No. 2487, 2489–2490, 2492, 2515, 2540–2541, 2556, 2576 adult, stained whole mounted specimen, P.122.10. 2 adult specimens in 70 % ethanol .

Further material examined. Two specimens for DNA analysis (1249, 1254).

Etymology. It was named after the two small diverticula of the spermatheca.

Diagnosis. (1) Small size (4.5–7 mm, in vivo), segments 24–33; (2) chaetae maximum 4 (5) per bundle, straight or slightly bent in a bundle arranged in asymmetric fan without nodulus; (3) five pairs of nephridia preclitellarly, anteseptale consisting of funnel only; (4) the dorsal lobes of pharyngeal glands in IV and V connected dorsally or touching each other, the third pair free, all with ventral lobes, one pair of secondary glands in VI; (5) dorsal blood vessel origin in XII, blood colorless; (6) intestinal diverticulum in IX–X; (7) sperm funnel expanded, pear-shaped 90–140 μm long, 2–3 times longer than wide (in vivo); (8) seminal vesicle absent; (9) spermatheca with 110–190 μm long and 16–20 μm wide ectal duct, one or two ectal glands, and a thin-walled ampulla with two diverticula-like protrusions and mostly two globular sperm mass in it; ampullae united proximally and connected jointly with the oesophagus; (10) 1–3 mature eggs at a time.

Description. Small enchytraeid worm. Holotype 4.65 mm long, 220 µm wide at VIII and 280 µm at clitellum (fixed), 31 segments. Length of paratypes 4.5–7.0 mm, width 220–290 µm at VIII and 240–340 µm at clitellum in vivo, length of fixed specimens 3.1–4.3 mm, width 190–280 µm at VIII and 210–320 µm at clitellum, segments (24)–29–33. Chaetal formula 3,4–4,3,2: 4,3,(5)–4,3,2. Chaetae straight or slightly bent without nodulus, in a bundle arranged in asymmetric fan, those towards dorsal and ventral midlines of body gradually smaller ( Fig. 2E View FIGURE 2 ), e.g. 37, 34, 29, 24 µm long in the ventral bundle of segment X. Maximum of length 30–41 µm in preclitellar region and posterior segments alike and about 2.5–3 µm wide, absent in XII. Epidermal glands conspicuous in vivo and in fixed specimens alike, in 5–6 transverse rows ( Fig. 2C View FIGURE 2 ). Body wall 18–27 μm thick, cuticle less than 1 μm. Clitellum extending over XII– ½ XIII, saddle-shaped, absent midventrally with about 65–82 µm distance, thinner posteriorly ( Fig. 2G View FIGURE 2 ). Clitellar gland cells irregularly scattered ( Fig. 2F View FIGURE 2 ). Head pore 0/I, longitudinal slit ( Fig. 2B View FIGURE 2 ).

Brain ( Fig. 2A View FIGURE 2 ) about 100–140 μm long in vivo and 90–110 μm fixed, 1.5–2 times longer than wide, anteriorly slightly concave, posteriorly truncated. Oesophageal appendages absent. Postpharyngeal bulbs well developed. Pharyngeal glands united in IV and V dorsally, sometimes only touching each other, the third pair free, all with ventral lobes ( Fig. 2J View FIGURE 2 ), and one small pair of secondary glands in VI ( Fig. 2K View FIGURE 2 ). Intestinal diverticula in IX–3 / 4X, conspicuous when well-developed, as a fusion of four diverticula-like protrusions ( Figs 3 View FIGURE 3 A–B), sometimes only a widening is visible ( Figs 3 View FIGURE 3 C–D). 140–200 μm wide in vivo (160–250 μm when fixed) about 30–60 μm wider than wide the intestine before and after the diverticula. Chloragocytes about 15–25 μm high. Dorsal blood vessel from XII, blood colorless; the anterior bifurcation in peristomium. Five pairs of preclitellar nephridia from 6/7 to 10/11; anteseptale consisting of funnel only, efferent duct arises antero-ventrally ( Figs 1B View FIGURE 1 , 2H View FIGURE 2 ). Coelomocytes ( Fig. 2H,I View FIGURE 2 ) oval mucocytes, granulated, about 22–33 μm long in vivo and fixed. Midgut pars tumida in XVIII–XXIV occupying 3–4 segments ( Fig. 2L View FIGURE 2 ). Seminal vesicle absent. Sperm funnels ( Figs. 3 View FIGURE 3 E–G) expanded pear-shaped 90–140 μm long, 2–3 times longer than wide in vivo, (65–130 μm long and 1.2–3 times longer than wide in fixed specimens), often appears hyaline entally. The collar narrower than the funnel body. Diameter of sperm ducts 6–7 μm. Spermatozoa 70–120 μm long, heads 30–50 μm in vivo (40–65 and 17–18 μm fixed, respectively). Male glandular bulb ( Figs 2G View FIGURE 2 , 3H View FIGURE 3 ) compact, well developed, spherical, diameter about 80–90 μm in vivo (47–70 μm, fixed). Spermathecae ( Figs 1A View FIGURE 1 , 3 View FIGURE 3 I–K, 6 C, E–F) attached to the oesophagus. Ectal ducts 110–190 μm long and 16–20 μm wide in vivo [90–135 μm long (in one case, only 60 μm) and 15–17 μm wide, fixed], canal at orifice 2.5–3 μm wide, distally widening slightly at ampulla into 6–8 μm width in vivo, with one or two ectal glands (sometimes the two glands have different length: 19–39 μm) ( Fig. 3K View FIGURE 3 ). Ampullae onion-shaped, when fully mature with two diverticula-like protrusions and mostly two (occasionally three) globular sperm masses in it ( Figs 6 View FIGURE 6 E–F). Ampullae united proximally and connect jointly with the oesophagus; 1–3 mature egg at a time.

Distribution and habitat. Only known from type locality in South Korea, at site 1: soil of mixed forest, Mt. Chiaksan, Hakgok-ri, Socho-myeon, Wonju-si, Gangwon-do (N 37˚23′36.50″, E 128˚03′15.30″), 395 m asl.

Differential diagnosis. D. diverticulatus sp. n. is similar to D. globulatus sp. n. in many traits (size, segments number, intestinal diverticula in IX–X, the shape of brain, the number of preclitellar nephridia (5), the type of chaetae, the size and form of sperm funnels, secondary pharyngeal glands in VI, seminal vesicle absent). For the principal differences, see the differential diagnosis of D. globulatus sp. n.