Amynthas taiwumontis, Shen, Huei-Ping, Chang, Chih-Han, Li, Chi-Lun, Chih, Wen-Jay & Chen, Jiun-Hong, 2013

Shen, Huei-Ping, Chang, Chih-Han, Li, Chi-Lun, Chih, Wen-Jay & Chen, Jiun-Hong, 2013, Four new earthworm species of the genus Amynthas (Oligochaeta: Megascolecidae) from Kinmen, Taiwan, Zootaxa 3599 (5), pp. 471-482 : 479-481

Amynthas taiwumontis sp. nov.

( Fig. 4 )

Holotype: Clitellate (mature) specimen (133 mm in total length, dissected) collected 1 May 2008 in front of Haiyin Temple (elevation 207 m), Mt. Taiwu, Kinmen by C. L. Li and Y. H. Lin (cat. no. 14-07399).

Other material. 2 specimens altogether. One aclitellate (cat. no. 14-07398) and one semi-clitellate (cat. no. 14-07400), same collection data as holotype.

Diagnosis. Small to medium; length 133–151 mm. Segments numbering 131–142. Setae 74–97 in VII, 73–89 in XX, and 16–22 between male pores. First dorsal pore in 11/12. Spermathecal pores small, four pairs in 5/6–8/9, 0.25–0.28 body circumference ventrally apart. Male pores 0.22–0.29 body circumference ventrally apart in XVIII, each inconspicuous on a round, slightly elevated porophore. Genital papillae absent. Spermathecae four pairs in VI–IX. Seminal vesicles small, two pairs in XI and XII, each vesicle with a round or elongated oval dorsal lobe. Prostate glands large, occupying four to nine segments in XVI–XXIV. Prostatic duct C- or S-shaped in XVIII–XIX. Accessory glands absent.

Description. External: Total length 133–151 mm. Weight 1.78–2.69 g. Segments numbering 131–142. Clitellum XIV–XVI, setae and dorsal pores absent, length 2.79–4.78 mm and width 3.32–4.77 mm. Prostomium epilobous. Setae 74–97 in VII, 73–89 in XX, and 16–22 between male pores in XVIII. First dorsal pore in 11/12. Spermathecal pores small, four pairs in intersegmental furrows of 5/6–8/9; distance between paired pores 0.25–0.28 body circumference ventrally apart. Genital papillae absent. Female pore single, mid-ventral in XIV. Male pores paired in XVIII, 0.22–0.29 body circumference ventrally apart, each inconspicuous on a round, slightly elevated porophore ( Fig. 4 A). Genital papillae absent. Preserved specimens grayish brown in color with dark to light brown clitellum.

Internal: Septa 5/6–7/8 and 10/11–13/14 thick and muscular, 8/9/10 absent. Nephridial tufts on anterior faces of 5/6/7. Gizzard large in VIII–X. Intestine enlarged from XV or XVI. Intestinal caeca paired in XXVII, each simple, long, extending anteriorly to XXI–XXIII, or bent in XXIV. Esophageal hearts in X–XIII. Spermathecae four pairs in VI–IX ( Fig. 4 B), ampulla round or elongated oval-shaped, surface wrinkled, 0.77–2.28 mm long and 0.46–1.25 mm wide, spermathecal stalk stout, 0.26–0.94 mm in length. Diverticulum long, proximal part slender and slightly enlarged toward distal end, but no specially enlarged seminal chamber, 1.03–3.78 mm in total length. Accessory glands absent. Holandric, testes large, oval, two pairs in ventrally joined sacs in X and XI. Seminal vesicles small, two pairs in XI and XII, anterior pair occupying half to full segmental compartment and posterior pair vestigial, occupying half segment, each vesicle with a round or elongated oval dorsal lobe. Prostate glands large, occupying four to nine segments in XVI–XXIV ( Figs. 4 C, D), racemose, divided into several lobules by grooves. Prostatic duct stout, C- or S-shaped in XVIII or XVIII–XIX. Accessory glands absent.

Etymology. The name taiwumontis is given to this species with reference to its type locality (elevation 207 m) at Mt. Taiwu in Kinmen.

Remarks. On the main island of Kinmen, Amynthas taiwumontis sp. nov. was only found in areas around Mt. Taiwu. It is octothecal, and has simple male pore structure and no genital papillae or genital markings. These characters are similar to Amynthas fornicatus ( Gates, 1935) from the west border of Sichuan, China. However, the two species can be easily distinguished by the external characters. A. fornicatus is smaller (length 80–94 mm and segments 90–105) and has much lower setal number than A. taiwumontis with 43–52 setae in VI–VIII and 45–55 setae in XXV for the former ( Chen 1936) and 74–97 setae in VII and 73–89 setae in XX for the latter.

Amynthas marenzelleri ( Cognetti, 1906) from Japan is octothecal and also has a simple male pore structure and no genital markings. It is different from A. taiwumontis by the larger body size (length 160–190 mm and diameter 6–7 mm) and lower setal number (36–43 setae in VII and 50–54 setae in XXIV) ( Cognetti 1906; Kobayashi 1938). In addition, A. marenzelleri has small prostate glands confined in XVIII and small spermathecae without diverticulum, whereas A. taiwumontis has large prostate glands occupying four to nine segments in XVI–XXIV and spermathecae with long diverticulum.

Amynthas sinabunganus ( Michaelsen, 1923) from Sumatra and Amynthas tertiadamae ( Michaelsen, 1934) from Gulf of Siam are also octothecal with simple male pore structure and without genital markings. However, the two species are distinguishable specifically from A. taiwumontis simply by their much smaller body size and lower setal number. Both are 52 mm long and 2–3 mm wide, with 104 segments for A. sinabunganus ( Michaelsen 1923) and 120 segments for A. tertiadamae ( Michaelsen 1934) . Setal numbers range from 23 to 40 per segment for A. tertiadamae ( Michaelsen 1934) and about 50 per segment for A. sinabunganus ( Michaelsen 1923) .

Figures

FIGURE 4. Amynthas taiwumontis sp. nov. Holotype (cat. no. 14 - 07399): (A) ventral view of male pore region (mp, male porophore); (B) dorsal view of right spermathecae (amp, ampulla; dv, diverticulum); (C) dorsal view of left prostate gland (pd, prostatic duct); (D) dorsal view of right prostate gland. Scale bar 1 mm.