Amynthas yuanjiangensis Sun & Qiu, 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 : 464-467

Amynthas yuanjiangensis Sun & Qiu , sp. nov.

( Fig. 4 )

Type material. Holotype: One clitellate specimen (C-YN201102-01), China, Yunnan Province, Yuanjiang National Nature Reserve (23°39ʹ54ʺN, 101°46ʹ29ʺE), 2096 m asl, by the side of a ditch, under chestnut tree, yellow cinnamon soil; Jul. 16, 2011; J. B. Jiang, J. Sun, X. D. Lei, and H. W. Feng coll.

Paratypes: A total of 55 specimens, as follows: One clitellate (C-YN201703-01), China, Yunnan Province, Yulong Snow Mountain Provincial Nature Reserve (27°12ʹ19.6ʺN, 100°16ʹ47.7ʺE), 1451 m asl; Aug. 2, 2017; J. B. Jiang, Y. Dong, Q. Zhao, and Z. Yuan coll. Nine clitellates (C-YN201713-06), China, Yunnan Province, Wuliangshan Nature Reserve (24°46ʹ22.9ʺN, 100°31ʹ12.4ʺE), 2158 m asl; Aug. 5, 2017; J. B. Jiang, Y. Dong, Q. Zhao, and Z. Yuan coll. Nine clitellates (C-YN201719-01), China, Yunnan Province, Dali City, Cangshan National Nature Reserve (25°46ʹ55.1ʺN, 100°05ʹ27.4ʺE), 2364 m asl; Aug. 6, 2017; J. B. Jiang, Y. Dong, Q. Zhao, and Z. Yuan coll. Four clitellates (C-YN201722-01), China, Yunnan Province, Dali City, Yunlong Tianchi National Nature Reserve (25°51ʹ42.1ʺN, 99°17ʹ00.7ʺE), 2621 m asl; Aug. 7, 2017; J. B. Jiang, Y. Dong, Q. Zhao, and Z. Yuan coll. Two clitellates (C-YN201735-08), China, Yunnan Province, Dehong Dai and Jingpo Autonomous Prefecture, Tongbiguan Provincial Nature Reserve (24°08ʹ56.3ʺN, 98°01ʹ31.0ʺE), 957 m asl; Aug. 11, 2017; J. B. Jiang, Y. Dong, Q. Zhao, and Z. Yuan coll. Two clitellates (C-YN201749-01), China, Yunnan Province, Yongdedaxueshan Nature Reserve (25°09ʹ03.1ʺN, 99°42ʹ31.4ʺE), 2122 m asl, 14 Aug. 2017; J. B. Jiang, Y. Dong, Q. Zhao, and Z. Yuan coll. One clitellate (C-YN201756-04), China, Yunnan Province, Lincang City, Nangunhe National Nature Reserve (23°38ʹ58.3ʺN, 99°20ʹ32.9ʺE), 1429 m asl; Aug. 16, 2017; J. B. Jiang, Y. Dong, Q. Zhao, and Z. Yuan coll. Two clitellates (C-YN201762-05), China, Yunnan Province, Lincang City, Nangunhe National Nature Reserve (23°18ʹ54.9ʺN, 99°13ʹ14.4ʺE), 2129 m asl; Aug. 17, 2017; J. B. Jiang, Y. Dong, Q. Zhao, and Z. Yuan coll. Nine clitellates and four aclitellates (C-YN201627-02), China, Yunnan Province, Pu’er City , Jingdong Yi Autonomous County (24°16ʹ09.5ʺ N, 100°45ʹ37.3ʺ E), 1860 m asl, in black sandy soil; Jul. 30, 2016; X. Gao, Y. F. Lu, J. Z. Jiang, J. Long coll. Two clitellates and three aclitellates (C-YN201703-01), China, Yunnan Province, Lijiang City, Yulong Snow Mountain Provincial Nature Reserve (27°12ʹ07.2ʺN, 100°16ʹ51.9ʺE), 3140 m asl, in yellow soil; Aug. 2, 2017; Z. Yuan, J. B. Jiang, Y. Dong, Q. Zhao coll. Four clitellates (C-YN201722-01), China, Yunnan Province, Dali City, Yunlong Tianchi National Nature Reserve (25°51ʹ30.7ʺN, 99°17ʹ03.7ʺE), 2621 m asl, in brown soil; Aug. 7, 2017; Z. Yuan, J. B. Jiang, Y. Dong, Q. Zhao coll. Six aclitellates (C-YN201756-04), China, Yunnan Province, Lincang City, Nangunhe National Nature Reserve (23°38ʹ49.0ʺN, 99°20ʹ36.6ʺE), 1429 m asl, in yellow cinnamon soil; Aug. 16, 2017; Z. Yuan, J. B. Jiang, Y. Dong, Q. Zhao coll. Two clitellates (C-YN201735-08), China, Yunnan Province, Dehong Dai and Jingpo Autonomous Prefecture, Tongbiguan Provincial Nature Reserve (24°08ʹ46.1ʺN, 98°01ʹ32.3ʺE), 957 m asl, in brown soil; Aug. 11, 2017; Z. Yuan, J. B. Jiang, Y. Dong, Q. Zhao coll. Two clitellates (C-YN201762-05), China, Yunnan Province, Lincang City, Nangunhe National Nature Reserve (23°18ʹ45.2ʺN, 99°13ʹ17.4ʺE), 2129 m asl, in brown soil; Aug. 17, 2017; Z. Yuan, J. B. Jiang, Y. Dong, Q. Zhao coll. The habitats of the paratypes were not recorded in detail.

Etymology. The name yuanjiangensis is derived from the collection site (Yuanjiang National Nature Reserve) of the holotype. In Chinese, Amynthas yuanjiangensis is Kmũ Ḃḋ.

Diagnosis. Medium-sized; four pairs of spermathecal pores in 5/6–8/9; each male pore on the top of a large raised pulvinate pad; no genital papillae in the spermathecal pore and male pore regions; prostate gland partially vestigial in 1/2 XVII–1/2 XIX, or developed; spermathecal diverticulum about ¾ as long as the main spermathecal axis, distal U dilated into a rod-shaped seminal chamber.

Description. External characters: Preserved specimens yellowish-brown on dorsum, lacking pigment on ventrum. Mid-dorsal line pigmented. Dimensions 80–135 mm by 3.0–5.0 mm at clitellum; segments 82–110. Secondary annulations present in VI–XIII. Prostomium ¾ epilobous. First dorsal pore in 11/12. Clitellum annular, in XIV–XVI, gray-brown, smooth, swollen, no setae on the ventral side; dorsal pores absent but with vestiges on clitellum. Setae uniformly distributed, 22–30 at III, 30–36 at V, 32–36 at VIII, 38–48 at XX, 46–62 at XXV; 7–9/VII, 7–14/VIII between spermathecal pores, 7–12 between male pores; setal formula AA=1.0–1.2AB, ZZ=1.2–1.3ZY. Spermathecal pores four pairs in 5/6–8/9 ( Fig. 4a , sp.p), ventrally separated by slightly more than 0.33 of circumference. Male pores in XVIII, ventrally separated by 0.25 of circumference, each on top of a large raised pulvinate pad, surrounded by two skin folds medially and one rhombus-shaped skin fold laterally in the holotype ( Fig. 4a , mp), but no skin fold in paratypes. No genital papillae in male pore region. Female pore single, mid-ventral in XIV, elliptical.

Internal characters: Septa 8/9–9/10 absent, 5/6–7/8 thickened and muscular, 10/11–14/15 thicker than those following. Dorsal blood vessel single, continuous onto pharynx; esophageal hearts 4 pairs in X–XIII, all developed. Gizzard bucket-like, in VIII–X; intestinal swelling in XV. Intestinal caeca between simple and complex, originating in XXVII and extending forward to 1/2XXIII, horn-shaped sacs; tiny incisions deeper on dorsal margin than on ventral margin in holotype ( Fig. 4b ); tiny incisions only on dorsal margin in paratypes C-YN201703-01, CYN201703-01, C-YN201719-01, and C-YN201735-08. Male organs: testis sacs in X and XI; oval, developed, two lobes connected ventromedially in the first pair and separated ventromedially in the second pair; two pairs of seminal vesicles in XI and XII, first pair separated ventromedially, second pair connected with a slim tube; in holotype, left prostate gland located in 1/2 XVII–1/2 XIX and degenerated into a small and compact lobe, right prostate gland pachytic and developed ( Fig. 4c ), its duct in XVIII, U-shaped, stout ventrally; prostate glands vestigial in paratypes C-YN201703-01, C-YN201719-0, and C-YN201735-08, but developed in paratype C-YN201713-06; no visible accessory glands on XVIII. Spermathecae paired in VI–IX, about 2.7 mm long; spermathecal ampulla heart-shaped, 2.1 mm long; in holotype, diverticulum about 3/4 as long as the main spermathecal axis, distal 2/5 dilated into a rodshaped seminal chamber; in paratypes C-YN201703-01, C-YN201713-06, C-YN201722-01, and C-YN201735-08, diverticulum about 1/2 as long as the main spermathecal axis, distal 1/2–1/3 dilated into rod-shaped seminal chamber; in paratype C-YN201719-01, diverticulum about 2/5 as long as the main spermathecal axis, distal 1/3 dilated into rod-shaped seminal chamber; no nephridia on spermathecal ducts ( Fig. 4d ).

Variation. The prostate glands are either degenerated or developed.

DNA barcodes. GenBank accession numbers KF205466 (C-YN201102-01, holotype), MH 845539 (CYN201703-01, paratype), MH 845531 (C-YN201713-06, paratype), MH 845522 (C-YN201719-01, paratype), MH 845514 (C-YN201722-01, paratype), MH 845487 (C-YN201735-08, paratype), MH 845470 (C-YN201749- 01, paratype), MH 845460 (C-YN201756-04, paratype), MH 845451 (C-YN201762-05, paratype), MH 837679 (C-YN201627-02, paratype), MH 845539 (C-YN201703-01, paratype), MH 845514 (C-YN201722-01, paratype), MH 845460 (C-YN201756-04, paratype), MH 845487 (C-YN201735-08, paratype), MH 845451 (C-YN201762-05, paratype) .

Remarks. A. yuanjiangensis sp. nov. keys to the Amynthas corticis -group ( Sims & Easton, 1972), characterized by four spermathecal pores located intersegmentally in 5/6–8/9 and by holandry. By now, there are 109 species belonging into A. corticis -group totally ( Nguyen et al. 2020a). The combined characters of medium-sized body, male pore on the top of a large raised pulvinate pad, no genital papillae in the spermathecal pore and male pore regions, intestinal caeca between simple and complex, prostate gland partially vestigial or developed, and rod-shaped spermathecal seminal chamber make this new species different from the species reported from China in A. corticis -group.

This new species is similar to Amynthas fornicates (Gates, 1935) in medium-sized body, no genital papillae in the male pore region, and the arrangement of spermathecal pores. However, in A. yuanjiangensis sp. nov., the intestinal caeca are between simple and complex, the prostate glands are partially degenerated, and the spermathecal diverticulum shorter than the main spermathecal axis; however, in A. fornicates , the intestinal caeca are simple, the prostate glands are developed, and the spermathecal diverticulum is longer than the main spermathecal axis.

A. yuanjiangensis sp. nov. is resemble Amynthas homochaetus (Chen, 1938) in the large raised pulvinate pad of male pore area, no genital papillae on spermathecal pore region and male pore region especially. But A. yuanjiangensis sp. nov. is clearly distinguished from A. homochaetus by the following characters: 1) the intestinal caeca in A. homochaetus are simple, but in this new species, they are between simple and complex; 2) the prostate glands in A. homochaetus are well developed, but in the new species, they are partially degenerated; 3) the seminal chambers in A. homochaetus are ovoid, but those in the new species are rod-shaped.

Amynthas disperses Sun & Qiu, 2018 and A. yuanjiangensis sp. nov. have both been collected in several localities in South China, and share some characters (e.g. megium-sized body, the area of male pore porophore is bigger, partially vestigial prostate gland, and band- or rod-shaped seminal chamber), but they are different from each other in the following ways: 1) the first dorsal pore is located at 10/11 or 11/12 on A. disperses , but always at 11/ 12 in the new species; 2) small genital papillae are always present in the spermathecal pore and male pore region in A. disperses , but there are no genital papillae in the new species; 3) the intestinal caeca in A. disperses are simple, but those in this new species are between simple and complex; 4) the spermathecal diverticulum is about as long as the main spermathecal axis in A. disperses , but shorter than the main spermathecal axis in the new species.

Figures

FIGURE 4. Amynthas yuanjiangensis Sun & Qiu sp. nov., holotype. (a) Ventral view showing spermathecal pores (sp) and male pores (mp); (b) do., intestinal cecum; (c) do., prostate gland; (d) do., spermathecae. Scale bar = 1 mm.