Amynthas accessorius Qiu & Zhao, 2018

Zhao, Qi, Yao, Xuanzhu, Lan, Yaqiong, Xu, Junxian & Qiu, Jiangping, 2018, New earthworm species of the genus Amynthas from Hainan Island, China (Megascolecidae, Clitellata), Zootaxa 4496 (1), pp. 279-286 : 281-282

Amynthas accessorius Qiu & Zhao , sp. nov.

( Figure 2 )

Type material. Holotype. One clitellate specimen (HN201515-01A), China, Hainan Province, Longmen Town, Longmen Mountain (19°41'44"N, 110°44'06"E), 30 m a.s.l., soil, coll. J.P. Qiu, Q. Zhao, J.B. Jiang, L.L. Zhang, Y. Dong, M.S. Chen, 4 June, 2015 . Paratype. One clitellate specimen (HN201515-01B), same data as for holotype .

Locality and habitat. The specimens were collected in yellow soil under a rubber plantation, Longmen Mountain , Longmen Town, Hainan province, China.

Etymology. This species is named for its accessory glands. "Accessorius" is medieval Latin and means "helper".

Diagnosis. Three pairs of spermathecal pores in 5/6–7/8, eye-like, about 0.33 circumferences ventrally apart. Male pores each on a round pulvinate protuberance in XVIII, about 0.33 body circumferences apart, paired ovoid genital papillae present above and below the setae circle in the inner side of the pore, surrounded by several skin folds.

Description. Preserved specimens without pigment. No secondary annulation, dorsal line conspicuous. Dimensions 78 and 80 mm by 2.7 and 3.0 mm at clitellum, segments 140 and 148; body cylindrical in cross section. Prostomium 1/2 epilobous. Setae numbering 44 and 48/III, 50 and 68/V, 66 and 76/VIII, 42 and 44/XX, 60 and 66/XXV; 8 between male pores; 24 and 26 (VII), 22 and 26 (VIII) between spermathecal pores. Setal formula AA=1.0–1.1 AB, ZZ=1.0–1.1 ZY. Clitellum annular XIV–XVI, whitish, smooth, setae visible. First dorsal pore 12/ 13. Three pairs of spermathecal pores in 5/6–7/8, ventral, eye-like, about 0.33 body circumferences apart ( Fig. 2A ). Male pores each on a round pulvinate protuberance in XVIII, about 0.33 body circumferences apart, paired ovoid genital papillae present pre- and post- setae in the inner side of the pore, both male pores and genital papillae are surrounded by several skin folds separately ( Fig. 2B ).

Septa 8/9, 9/10 absent, before 8/9 thick and muscular, 10/11–13/14 thick. Esophageal hearts in X–XIII. Gizzard in IX–X, barrel-shaped. Intestine distinctly enlarged from XIII. Intestinal caeca simple, originating in XXVII, extending anteriorly to XXIII. Spermathecae paired in VI–VIII; the first pair is smaller than the other two pairs. All ampullae ovoid, spermathecal duct slender, twice as long as ampulla. Diverticula differing: The seminal chamber could not been found in the first pair; the second diverticulum as long as 0.75 of main pouch, terminal half enlarged as irregular ovoid seminal chamber ( Fig. 2C ); the terminal half of the third diverticulum enlarged as zigzag seminal chamber ( Fig. 2D ). Male sexual system holandric, testis sacs invisible; seminal vesicles paired in XI–XII, the first pair invisible, the second pair invisible in right, degenerate in left. Prostates degenerated completely, only S-(holotype) or U-(paratype) shaped prostatic duct in XVIII ( Fig. 2E ). Two large massive accessory glands present in XVII and XIX on the right side, closely attached to the body wall ( Fig. 2F ); accessory glands lacking on the left side in both holotype and paratype.

Remarks. The testis sacs and seminal vesicles are almost invisible in Amynthas accessorius sp. nov. Its prostates are completely degenerate, only the prostatic duct is left. Therefore, A. accessorius sp. nov. may be considered as a parthenogenetic species. The new species belongs to the hawayanus -group with three pairs of spermathecal pores in 5/6–7/8 ( Sims & Easton 1972). After comparing the new species with all other species in this group ( Beddard 1892; Chen 1933, 1936, 1938, 1946; Chen & Hsu 1977; Cognetti 1909; Gates 1930, 1931, 1932, 1935, 1936; Goto & Hatai 1898, 1899; Hatai 1930; Kinberg 1867; Kobayashi 1934, 1936, 1938; Michaelsen 1892, 1922, 1923, 1934; Rosa 1891, 1896; Ude 1925; Zhao et al. 2009), we found that the present species is most similar to Amynthas bouchei ( Zhao et al. 2009) . They share the following characters: similar characteristics of male pore region, first dorsal pore in 12/13, septa 8/9–9/10 absent, intestinal caeca simple. However, there are also obvious differences between these two species. Individuals of A. accessorius sp. nov. are small, with a body length of 78 and 80 mm, while individuals of A. bouchei are larger, 225–286 mm long. The diverticulum of A. bouchei is longer than the main pouch, and the ental half is dilated and enlarged as seminal chamber. However, in the new species, the diverticulum, although variable, is never longer than the main pouch. The first pair is smaller than the other two pairs. The ampullae are all of same shape, ovoid, and with a slender spermathecal duct twice as long as the ampulla. However, the diverticula differ: In the first pair, the seminal chamber could not been found; in the the second pair, the diverticulum is 3/4 as long as the main pouch, and the terminal half is enlarged as an irregularly ovoid seminal chamber ( Fig. 2C ); in the third pair, the terminal half of the diverticulum is enlarged as a zigzagshaped seminal chamber ( Fig. 2D ). Although the prostates of these two species are not developed, the prostate is small in A. bouchei , while only the prostatic duct is left in the new species. There are accessory glands in A. accessorius sp. nov., but they are absent in A. bouchei . Both testis sacs and seminal vesicles are degenerate in the new species. Considering the differences in characters, we decided to give new species status to our specimens.

Figures

FIGURE 2. Amynthas accessorius sp. nov. A. Ventral body surface with spermathecal pores. B. Ventral body surface with male pores. C,D. Spermathecae. E,F. Prostates.