Amynthas ruiyenensis Shen, 2019

Shen, Huei-Ping, Chang, Chih-Han & Chih, Wen-Jay, 2019, Two new earthworm species of the genus Amynthas (Oligochaeta: Megascolecidae) from central Taiwan, with comments on some recent species assignments in Amynthas and Metaphire, Zootaxa 4658 (1), pp. 101-123 : 110-111

Amynthas ruiyenensis Shen , sp. nov.

( Figure 3 )

Holotype: Clitellate (mature) specimen (97 mm in total length, amputated, dissected), from roadside ditches in Ruiyen Creek Nature Reserve , Nantou County, 24°06'14.29''N, 121°10'34.01''E, 2195 m asl, 2 July 2009, T.-J. Lin & J.-H. Wu (TESRI-O-H-55; RY023, PCR failed).

Diagnosis. Length 97 mm (holotype). Segments numbering 111. Setae 65 in VII, 59 in XX, and 10 between male pores. First dorsal pore in 12/13. Clitellum XIV–XVI. Spermathecal pores four pairs in 5/6–8/9, 0.24–0.25 body circumference ventrally apart. Male pores 0.25 body circumference ventrally apart in XVIII, each on a round porophore about 0.67 mm in diameter. Genital papillae large, one pair in presetal XIX. Spermathecae four pairs in VI–IX. Seminal vesicles small to large, two pairs in XI and XII. Prostate glands lobed, paired in XVII–XX. Prostatic ducts S-shaped in XVIII. Accessory glands large, sessile, paired in XIX, corresponding to external genital papillae.

Description. External: Length (clitellate) 97 mm, weight 0.52 g in 95% ethanol. Segments numbering 111. Clitellum XIV–XVI, setae and dorsal pores absent, 4.63 mm in length and 3.59 mm in width. Prostomium epilobous. Two annuli (secondary segments) per segment in VIII–IX and three annuli per segment in X–XIII. Setae minute, vague, number 65 in VII, 59 in XX and 10 between male pores in XVIII. First dorsal pore in 12/13. Spermathecal pores four pairs in intersegmental furrows of 5/6–8/9, distance between paired pores 0.24–0.25 body circumference ventrally apart, ( Fig. 3A ). Genital papillae absent in the preclitellar region. Female pore single, mid-ventral in XIV. Male pores inconspicuous, paired in XVIII, 0.25 body circumference ventrally apart, each situated on a round porophore about 0.67 mm in diameter, surrounded by a circular skin fold ( Fig. 3B ). One pair of large genital papillae in presetal XIX ( Fig. 3B ), separated by 9 setae, each papilla about 1.06 mm in diameter. Live worms white. Preserved specimens white and pale brown on clitellum.

Internal: Septa 5/6–7/8 thick, 8/9/10 absent, 10/11–13/14 thick. Nephridial tufts dense, bush-like mass on anterior faces of 5/6/7. Gizzard large, round in VIII–X. Intestine enlarged from XVI. Intestinal caeca paired in XXVII, simple, extending anteriorly to XXV or XXIII. Esophageal hearts paired in XI–XIII. Spermathecae four pairs in VI–IX ( Fig. 3C ), ampulla elongated oval-shaped, 1.04–1.33 mm long and 0.7–0.86 mm wide, spermathecal duct stout, 0.44–0.56 mm in length. Diverticulum vestigial or long, tubular, 0.6–1.79 mm in total length, stalk slender, seminal chamber normal, iridescent to absent. Holandric. Testes large, oval, two pairs in ventrally joined sacs in X and XI. Seminal vesicles follicular, cotton-like, two pairs in XI and XII, variable in size: large one occupying an entire segmental compartment and small one about half of the segmental compartment. Prostate glands paired in XVII–XX ( Fig. 3D ), wrinkled and lobed. Prostatic ducts enlarged in the middle, S-shaped in XVIII. Accessory glands large, sessile, paired in XIX, 0.65 mm in width and 0.86 mm in length, corresponding to external genital papillae ( Fig. 3D ).

Etymology. The name ruiyenensis is given to this species with reference to its type locality in Ruiyen Creek Nature Reserve, Nantou, central Taiwan.

Remarks. Amynthas ruiyenensis sp. nov. is akin to A. dinghuensis from southwestern Taiwan in having four pairs of spermathecae in VI–IX and a pair of genital papillae in presetal XIX. However, the much smaller body size and genital papillae, lower segment and setal numbers, and stalked accessory glands of A. dinghuensis distinguish it from A. ruiyenensis . Amynthas longicauliculatus ( Gates, 1931) from Burma, Amynthas murayamai (Kobayashi, 1938) from Korea and Amynthas shimaensis ( Goto & Hatai, 1899) from Japan are also octothecal and have large, paired postclitellar genital markings. Compared with A. ruiyenensis , A. longicauliculatus is apparently much larger with body length of 140–244 mm and width of 7–10 mm, and has higher segment number (137–140) and three pairs of genital markings on 18/19, 19/20 and 20/21 ( Gates 1931). The position and size of genital papillae of A. ruiyenensis appear like those of A. murayamai , but the latter has higher segment number (137–139), lower setal numbers (42 in IX and 52 in XX) and wider spacing between paired spermathecal pores and male pores with about 0.45 and 0.3 ventral circumference, respectively ( Kobayashi 1938b). In addition, the reproductive organs of A. ruiyenensis and A. murayamai vary greatly: A. murayamai has small, equal-sized seminal vesicles, relatively large pseudovesicles in XIII, small prostate glands consisting of two main lobes in XVII–XVIII, thin prostatic ducts looped in a C- or L-shape, no accessory glands corresponding to external genital markings, and spermathecae with large diverticula ( Kobayashi 1938b). As to A. shimaensis , it is a large earthworm with a body length of 205 mm, a width of 7 mm, and 163 segments ( Goto & Hatai 1899). Its genital papillae are also larger with a diameter of about 2.5 mm and located in postsetal XIX rather than presetal XIX ( Goto & Hatai 1899).

Apart from all the aforementioned species, Amynthas omodeoi Zhao & Qiu, 2009 and Amynthas edwardsi Zhao & Qiu, 2009 from Hainan Island, China also have large, paired postclitellar genital papillae ( Zhao et al. 2009). However, both species are sexthecal with three pairs of spermathecae in VI–VIII and have coiled diverticula. A. omodeoi has much lower setal numbers with 26–27 in V and 30–36 in XX, papillae paired in 18/19, large prostate glands in XVII–XXIII, U-shaped prostatic ducts, and long stalked accessory glands ( Zhao et al. 2009). Like A. ruiyenensis , A. edwardsi also has paired papillae in presetal XIX, but it is also similar to A. omodeoi regarding the much lower setal numbers with 32–34 in V and 32–33 in XX, large prostate glands in 1/2XVI–XXIV and U-shaped prostatic ducts. A. ruiyenensis can be easily distinguished from A. omodeoi and A. edwardsi by these disparate features.

Figures

FIGURE 3. Amynthas ruiyenensis sp. nov. Holotype (TESRI-O-H-55). A. Ventral view of spermathecal pore region (sp, spermathecal pore). B. Ventral view of male pore region (mp, male porophore; gp, genital papilla). C. Dorsal view of right spermathecae (amp, ampulla; dv, diverticulum). D. Dorsal view of left prostate gland (pd, prostatic duct; ag, accessory gland). Scale bars = 1 mm.