Kahayandrilus tundaiensis, Ohtaka & Wulandari, 2016

Ohtaka, Akifumi & Wulandari, Linda, 2016, Description of Kahayandrilus tundaiensis gen. et sp. nov. (Annelida: Clitellata: Tubificinae) from Central Kalimantan, Indonesia, Species Diversity 21 (1), pp. 43-47 : 45-46

Kahayandrilus tundaiensis sp. nov.

( Figs 1–2 )

Type series. Holotype. MZB Oli. 0005, a whole-mounted unstained specimen from profundal bottom of Lake Tundai , depth 6 m, 3 May 2004 . Paratypes, all from the type locality: MZB Oli . 0006, a whole-mounted unstained specimen, 3 May 2004; USNM 1283362–1283363 , two wholemounted unstained specimens, 21 September 2004; ICHUM 5107–5111 , two whole-mounted unstained, and one sagittally and two cross sectioned specimens, stained in hematoxylin and eosin, 3 May and 21 September 2004 .

Other material. Seventeen whole-mounted, six sagittally and two cross sectioned specimens from the type locality and nearby sites in Lake Tundai, depth 3–6 m, 3 May and 21 September 2004.

Type locality. Profundal of Lake Tundai , Central Kalimantan, Indonesia .

Etymology. The specific epithet is derived from the type locality, Lake Tundai, Central Kalimantan, Indonesia.

Description. Body reddish in color when alive, not coiling up when stimulated. In mature and fixed state, body 13–18 mm long, 0.35–0.46 mm wide in segment VIII, and 0.50–0.63 mm in segment XI, with ventral side of XI flattened and oπen swollen laterally ( Fig. 1A ). Segments up to 110. Body wall naked and without pigments. No secondary annulation. Prostomium bluntly conical, 140–160 µm long and 90–120 µm wide in fixed individuals. Clitellum formed by a single layer of glandular cells 24–32 µm in height, extended from beginning of XI to the end of XII and less developed around male pores ( Fig. 1A ). One pair of male pores opening ventrally on the chaetal line at mid-XI ( Fig. 2F ).

All chaetae bifurcated crotchets, their shape and number not different in ventral and dorsal bundles. Chaetae in preclitellar segments ( Fig. 1B ) 4–7 per bundle, 80–96µm long, with nodulus at 1/3 from distal end and with upper tooth longer and as thick as the lower; those in postclitellar segments ( Fig. 1C ) 1–3 per bundle (mostly 2 in middle segments and mostly 1 in posterior segments), 64–85 µm long, with nodulus at 1/3–1/4 from distal end and with upper tooth a little longer or slightly shorter and thinner than the lower. No intermediate teeth. In fully mature worms, both dorsal and ventral chaetae decreased to 1–3 per bundle in X and oπen entirely missing in XI. No modified genital chaetae.

Coelomocytes not observed. Commissural blood vessels connecting dorsal and ventral vessels from I through VII, forming loops in each segment. Pharynx in II and III, with high epithelium and several clusters of glandular cells dorsally ( Fig. 2A ). Pharyngeal glands dorsally in IV and V. Chloragogen cells on gut from VI on. Intestine from VIII on, not abruptly widening.

Male genitalia paired. One pair of testes in X and one pair of ovaries in XI. Sperm sac from IX to XI, containing complete sperms. Egg sac extending backwards to XIII. Sperm funnel large, 150 µm in diameter, located in ventral part of septum 10/11. Vas deferens long and coiled up, 12–16 µm wide throughout course, with lumen 6–8 µm, ciliated, entering atrium apically ( Fig. 1D ). Atrial ampulla ovoid, 110 µm long, maximum 80 µm wide, with thick (16–30 µm) and granulated inner epithelium and with thin (less than 3 µm) outer muscle layer ( Fig. 2C ). A solid prostate gland almost as large as atrium, connected with that at 1/3 of ental portion through short stalk ( Figs 1D , 2B ). Ejaculatory duct long (420µm long), not winding and non-glandular, almost uniform in width (14–19 µm) throughout course with lumen about 10 µm in diameter. Large penis set in deep and narrow penial pouch opening ventrally in XI ( Fig. 2F ). Penis conical, 110–120 µm long, 50–105 µm wide at base, with thin (1.6–3 µm) inner epithelium and with thick (10–12 µm) subepithelial layer of connective tissue staining well with eosin ( Fig. 2D, E ). Cuticle layer on penis a little thicker than integumentary cuticle but not forming any distinct penial sheath. None of 19 specimens examined with male ducts had completely or partially developed, nor vestigial spermathecae.

Distribution and habitat. The present species was collected from muddy bottom in Lake Tundai, an oxbow lake in Kahayan River system in Central Kalimantan. The lake water is acidic and brownish in color due to high amount of humic substances derived from a tropical bog, with the pH ranging from 3.9 to 4.6 ( Ohtaka et al. 2014). The lake is 3–6 m deep, the bottom temperature ranged from 27 to 29°C and the concentration of dissolved oxygen in the bottom waters ranged from 0.7 to 1.1 mgl −1 ( Ohtaka et al. 2014). Chiromonid larvae were predominant in the zoobenthos of Lake Tundai, followed by oligochaetes ( Iwakuma et al. 2008). Aulophorus , Dero , Branchiura , Limnodrilus , and two more, uncertain oligochaete taxa were recorded from the lake bottom ( Iwakuma et al. 2008).

Figures

Fig. 1. Kahayandrilus tundaiensis gen. et sp. nov. (A) Lateral view of anterior segments in a non-type specimen; (B) dorsal chaeta in III in holotype (MZB Oli. 0005); (C) the same in a posterior segment; (D) male duct from a dissected specimen in paratype (MZB Oli. 0006).

Fig. 2. Kahayandrilus tundaiensis gen. et sp. nov. (A) Sagittal section of anterior segments in paratype (ICHUM 5110); (B) sagittal section of atrium together with prostate gland in paratype (ICHUM 5110); (C) cross section of atrium together with prostate gland in paratype (ICHUM 5110); (D) penis in holotype (MZB Oli. 0005); (E) sagittal section of penis in paratype (ICHUM 5109); (F) cross section of X at the line of male pore in paratype (ICHUM 5111).