Amynthas scaberulus Sun & Jiang, 2021

Sun, Jing, Jiang, Ji-Bao, Wu, Juzhen, Yuan, Zhu & Qiu, Jiang-Ping, 2021, Three new widely distributed and polymorphic species of Amynthas earthworms (Oligochaeta, Clitellata, Megascolecidae) from South China, Zootaxa 4938 (4), pp. 457-474 : 462-464

Amynthas scaberulus Sun & Jiang , sp. nov.

( Fig. 3 )

Type material. Holotype: One clitellate specimen (C-SC201007-02), China, Sichuan Province, Pingshan County (28°47ʹ32ʺN, 104°01ʹ41ʺE), 411 m asl, under bamboo and tea plants, red-yellow soil; Aug. 14, 2010; J. Sun, Z. W. Yi, and J. H. Yi coll.

Paratypes: A total of seven specimens, as follows: Four clitellates (C-HU201615-01(1)), China, Hunan Province, Mount Shunhuang (26°31ʹ25ʺN, 111°21ʹ44ʺE), 302 m asl, under moss, fern, bushes, and deciduous tree, redyellow soil; May 5, 2016; J. Sun, J. B. Jiang, Y. Dong, and Y. Zheng coll. One clitellate (C-HU201614-11), China, Hunan Province, Mount Shunhuang (26°29ʹ19ʺN, 111°21ʹ06ʺE), 221 m asl, under moss, fern, bushes, and deciduous tree, red-yellow soil; May 5, 2016; J. Sun, J. B. Jiang, Y. Dong, and Y. Zheng coll. Two aclitellates (C-SC201717- 01), China, Sichuan Province, Pengzhou City, Baishuihe National Nature Reserve (31°12ʹ01.2ʺN, 103°44ʹ04.3ʺE), 1147 m asl, in brown soil; May 12, 2017; Z. Yuan, J. B. Jiang, Y. Dong, X. Gao, and Z. M. Tao coll.

Etymology. The species name was derived from the Latin word “ scabra ”, meaning rough, because its skin looks rough. In Chinese, Amynthas scaberulus is ffiơũḂḋ.

Diagnosis. Medium-sized; two pairs of spermathecal pores in 7/8–8/9, the lower edge of each spermathecal pore forming a tiny papilla; each male pore on an elliptical and glandular porophore slightly elevated from the shallow skin sheath, each surrounded by one or two genital papillae; prostate glands developed or degenerated; spermathecal diverticulum shorter than the main spermathecal axis, distal ¼ dilated into a peach-shaped seminal chamber; accessory gland present or absent in the spermathecal region.

Description. External characters: Preserved specimens light gray before clitellum and gray after clitellum on dorsum, lacking pigment before clitellum and cinnamon after clitellum on ventrum. Mid-dorsal line pigmented after clitellum. Dimensions 129–166 mm by 4.5–6.0 mm at clitellum; segments 129–131. Secondary annulations present in VIII–XIII in the holotype, absent in paratypes. Prostomium ½ epilobous. First dorsal pore on 10/11 or 11/12. Clitellum annular in XIV–XVI, pale, smooth, swollen, no setae on the ventral side, dorsal pores usually absent. Setae uniformly distributed, 21–38 on III, 32–46 on V, 46–52 on VIII, 56–62 on XX, 52–74 on XXV; 16–26/VIII between spermathecal pores, 14–20 between male pores; setal formula AA=1.0–1.3AB, ZZ=1.2–2.0ZY. Two pairs of spermathecal pores in 7/8–8/9 ( Fig. 3a , sp.p), separated ventrally by about 0.33 of circumference. In the holotype, C-SC201007-02, a tiny papilla formed by the lower edge of each spermathecal pore ( Fig. 3a , gp); in paratype C-HU201615-01(1), one small papilla medial and posterior to each right spermathecal pore, or two small papillae medial to each spermathecal pore. Male pores in XVIII, separated ventrally by 0.33 of circumference, elliptical; glandular male porophore slightly elevated from the shallow skin sheath ( Fig. 3a , mp). In the holotype, each male pore surrounded by one genital papilla anterior and medial to the male pore ( Fig. 3a , gp); in paratype C-HU201615- 01(1), two genital papillae, one anterior and medial to the male pore, another posterior and medial to the male pore ( Fig. 3b ). Male pores and papillae together surrounded by 3–4 circular ridges. Female pore single, mid-ventral in XIV, milk-white, elliptical.

Internal characters: Septa 8/9–9/10 absent, 5/6–6/7 and 10/11–11/12 thickened and muscular, 7/8 and 12/13– 13/14 thicker than those following. Dorsal blood vessel single, continuous onto pharynx; esophageal hearts 4 pairs in X–XIII, the first pair slimmer than the others. Gizzard bucketlike, in VIII–X; intestinal swelling in XVI; in the holotype, intestinal caeca between simple and complex, originating in XXVII and extending forward to XXIII, horn-shaped sacs, smooth on dorsal margins, tiny incisions present after the upper ¼ on ventral margins ( Fig. 3c ); in paratype C-HU201615-01(1), intestinal caeca simple. Male organs: testis sacs in X and XI, oval, developed, two lobes separated ventromedially; seminal vesicles in XI, XII, underdeveloped, separated ventromedially; prostate gland degenerated into a single duct on the left side and small but hypertrophic on the right side in the holotype ( Fig. 3d ), but developed in paratype C-HU201615-01(1) ( Fig. 3e ); no visible accessory glands on XVIII. Spermathecae of holotype paired in VIII–IX, about 1.5 mm long; spermathecal ampulla ball-shaped, its duct stout, duct as long as ampulla; diverticulum shorter than the main spermathecal axis, distal ¼ dilated into a peach-shaped seminal chamber; in the holotype, a stalked accessory gland attached to the body wall and close to the root of the spermathecae; in the paratypes, no accessory gland; no nephridia on spermathecal ducts ( Fig. 3f ).

Variation. The prostate glands may be either fully developed or degenerated, and this variation can occur in a single individual.

DNA barcodes. GenBank accession numbers KF179570 (C-SC201007-02, holotype) , MF541646 (C- HU201615-01(1), paratype) , MF541647 (C-HU201614-11, paratype) , and MH 843384 (C- SC201717-01, paratype) .

Remarks. Amynthas scaberulus sp. nov. is classified into the Amynthas aeruginosus -group characterized by having two pairs of spermathecal pores in 7/8–8/9 and holandric ( Sims & Easton 1972). This group contains 73 species including subspecies by now ( Dong et al. 2020; Nguyen et al. 2020a). The combined characters of two pairs spermathecal pores in 7/8–8/9, a tinny papilla on the lower edge of each spermathecal pore, male pores accompanied by one or two genital papilla medially, intestinal caeca between simple and complex or simple, prostate gland degenerated partially, and spermathecae accompanied by a stalked accessory gland sometimes make A. scaberulus sp. nov. different from previously reported species from China in the A. aeruginosus -group. Considering body size, setal density, spermathecal pores location and its genital papillae, and male pore papillae, A. scaberulus sp. nov. is somewhat similar to the cosmopolitan species Amynthas robustus (Perrier, 1872) .

A. robustus is a polymorphic species. Here, we compare the new species with the Taiwan morph recorded by Chang et al. (2009 a), the Hong Kong and Zhejiang (originally written CheKiang) morph recorded by Chen (1935), and the Burma morph recorded by Gates (1972). The present new species and A. robustus share the following characters: 1) medium size; 2) similar setal density; 3) two pairs of spermathecal pores in 7/8–8/9, with similar genital papillae present in the spermathecal pore region; 4) male pore papillae elevated from the skin sheath, with each male pore near one or two genital markings. However, they have some differences: 1) the first dorsal pore may be in 10/11 or 11/ 12 in the new species, but is always in 11/ 12 in A. robustus ; 2) the clitellum occupies XIV–XVI in the new species, but although it occupies XIV–XVI in most A. robustus morphs (entire Taiwan and Burma morphs, most specimens of the Hong Kong morph), it may rarely be extended across two-thirds of segment XVII (one specimen of the Hong Kong morph); 3) the intestinal caeca are simple or between simple and complex in the new species, but simple in all examined morphs of A. robustus ; 4) the prostate glands may be degenerated or developed on the new species, but are always developed in A. robustus . In addition, the spermathecae are partially similar in the new species and A. robustus , as they have a similar shape, and accessory glands are present and stalked in some specimens for both species; the diverticulum is shorter than the spermathecal main axis in the new species, but this is not always the case in A. robustus .

Regarding the combined characters of body size, setal density, arrangement of spermathecal pores, and male pore shape, A. scaberulus sp. nov. also resembles the endemic species Amynthas flexuosus Qiu & Zhao (2017) , collected from Hainan Island, China ( Zhao et al. 2017). In detail, they have a similar body size (Dimensions 129–166 mm by 4.5–6.0 mm for the new species, and 112 mm by 6.5 mm for A. flexuosus ), setal density (21–38 on III, 32–46 on V, 46–52 on VIII, 56–62 on XX, 52–74 on XXV for the new species, and 48/III, 44/V, 52/VIII, 60/XX, 64/XXV for A. flexuosus ), spermathecal pore configuration (two pairs in 7/8–8/9 for both species), and male pore shape (male pore on a protuberance, surrounded by one genital papilla anterior and medial to the male pore, and the male pore and papilla together surrounded by several circular ridges). However, the intestinal caeca simple (smooth on dorsal and ventral margins) or between simple and complex (with tiny incisions on ventral margins) in the new species, but are always between simple and complex (with several finger-shaped saccule on dorsum) in A. flexuosus . Moreover, the spermathecal duct is as long as the ampulla in the new species, but very short, only 0.2 of the ampulla, in A. flexuosus ; the spermathecal diverticulum is shorter than the main spermathecal axis in the new species, with the distal ¼ dilated into a seminal chamber, but in A. flexuosus , the diverticulum is almost equal in size to the main spermathecal pouch, with the terminal ½ enlarged as a slightly zigzag seminal chamber; and the prostate gland may be degenerated or developed in the new species, but is always well developed in A. flexuosus .

Figures

FIGURE 3. Amynthas scaberulus Sun & Jiang sp. nov. (a) Ventral view showing spermathecal pores (sp), male pores (mp), and genital papillae (gp) of holotype; (b) do., male pore of paratype C-HU201615-01(1); (c) do., intestinal cecum in holotype; (d) do., prostate glands in holotype; (e) do., prostate gland in paratype C-HU201615-01(1); (f) do., spermathecae in holotype. Scale bar = 1 mm.