Amynthas dissimilis Qiu & Jiang, 2018

Jiang, Ji-Bao, Dong, Yan, Yuan, Zhu & Qiu, Jiang-Ping, 2018, Three new earthworm species of the tokioensis - group in the genus Amynthas (Oligochaeta: Megascolecidae) from Guangxi Province, China, Zootaxa 4496 (1), pp. 269-278 : 270

Amynthas dissimilis Qiu & Jiang , sp. nov.

( Figure 1 )

Holotype. Clitellate specimen (C-GX201302-12): China, Guangxi Province, Shiwan Mountain Nature Reserve (N 21.50594°, E 107.54579°), 242 m asl, black sandy topsoil under bryophytes in a ravine, 12th May, 2013, J. P. Qiu, Y, Hong, J. B. Jiang, L. L. Zhang and Y. Dong coll.

Paratypes. 15 clitellate specimens (C-GX201305-11): China, Guangxi Province, Shiwan Mountain Nature Reserve (N 21.502396°, E 107.53350°), 494 m a.s.l., black sandy topsoil under bryophytes besides road, 13th May, 2013, J. P. Qiu, Y, Hong, J. B. Jiang, L. L. Zhang and Y. Dong coll.

Etymology. The species is named after its main characteristics, which are different from other earthworms.

Diagnosis. Dimensions 125–142 mm by 5.8–7.0 mm at clitellum, segments 107–122. First dorsal pore in 10/ 11. Setae numbering 21–26 at III, 24–30 at V, 33–40 at VIII, 53–58 at XX, 52–62 at XXV; 10–12 between male pores, 12–14 between spermathecal pores. Spermathecal pores two pairs in 6/7–7/8, 0.33 circumference ventrally apart from each other. Male pores one pair in XVIII, 0.33 circumference apart ventrally, each on top of a slightly raised, round porophore, with two genital papillae that are concave at the top, present in each pulvinate pad surrounded by 5–8 circular ridges. Prostate glands developed. Testis sacs and seminal vesicles small. Ampulla ballshaped, stout duct as long as 1/4 ampulla. Diverticulum slightly longer than half main pouch, terminal half dilated into a swollen seminal chamber. Stalked accessory glands observed near spermathecae.

External characters. Light purple pigment on pre-clitellar dorsum, and light khaki pigment on ventrum and post-clitellar dorsum. Dimensions 125–142 mm by 5.8–7.0 mm at clitellum, segments 107–122. Prostomium 1/2 epilobous. First dorsal pore in 10/11. Setae numbering 21–26 at III, 24–30 at V, 33–40 at VIII, 53–58 at XX, 52–62 at XXV; 10–12 between male pores, 12–14 between spermathecal pores; setal formula: AA=1.2–1.6AB, ZZ=1.4– 1.6ZY. Clitellum annular, dark grey, in XIV–1/4XVII, setae invisible externally. Spermathecal pores two pairs in 6/ 7–7/8, ventral, eye-like, 0.33 circumference ventrally apart from each other. 8 tiny genital papillae present in anterior and posterior of each spermathecal pore ( Fig. 1A ). Male pores one pair in XVIII, 0.33 circumference apart ventrally, each on the top of a slightly raised, round porophore in a pulvinate pad. Two genital papillae, concave on top, one laterally posterior, one anterior, present in each pulvinate pad, the latter surrounded by 5–8 circular ridges ( Fig. 1B ). Female pore single in XIV, ovoid, milky white.

Internal characters. Septa 5/6–7/8 thick and muscular, 10/11–13/14 slightly thickened, 8/9–9/10 absent. Gizzard bucket-shaped, in IX–X. Intestine enlarged distinctly from XVI. Typhlosole medium from XXVII. Intestinal caeca paired in XXVII, smooth on dorsal margin, about 8 constrictions on ventral margin, extending anteriorly to XXI ( Fig. 1D ). Esophageal hearts in X–XIII. Ovaries in XIII. Spermathecae two pairs in VII and VIII, 1.2–2.0 mm long. Ampulla ball-shaped; duct stout, as long as 1/4 ampulla. Diverticulum slightly longer than half main pouch (ampulla and duct), terminal 1/2 dilated into a swollen, long heart-shaped seminal chamber. Two stalked accessory glands present near the duct of spermathecae ( Fig. 1C ). Holandric: Testis sacs two pairs, in X– XI, round, undeveloped, the posterior pair slightly larger than the anterior pair. Seminal vesicles two pairs, small, in XI–XII, the posterior pair also slightly larger than the anterior one. Prostate glands developed, inserting in XVIII and extending from 1/2XVI to 1/2XXI, coarsely lobate, prostatic duct U-curved, slightly thicker at the distal part. No accessory glands observed.

Remarks. The present species, A. dissimilis sp. nov., appears to be similar to A. vividus ( Chen, 1946) of the tokioensis -group in the characteristics of male pores, intestinal caeca and prostate glands. The male pores of both species are located on top of a small, round porophore that is surrounded by several circular ridges. The species differ in body size, segment number, first dorsal pore, clitellum, setal formula, genital papillae, septa of 8/9, testis sacs, seminal vesicles, spermathecae and accessory glands ( Table 1). A. dissimilis is a larger worm (125–142 mm length), with smaller testis sacs and seminal vesicles than A. vividus , and its clitellum is in XIV–1/4XVII. A. vividus is about 80 mm long, has large testis sacs, developed seminal vesicles, and regularly extended clitellum in XIV–XVI. Besides, spermathecae of A. vividus are absent or present in VII and VIII; when present, its irregular ampulla and long duct are quite different from the ones in A. dissimilis . Table 1 lists in detail the differences among the first two new species and other species of the tokioensis -group with similar characteristics.

Figures

FIGURE 1. Amynthas dissimilis Qiu & Jiang, sp. nov. A. Region of spermathecal pores, ventral view. B. Region of male pores, ventral view. C. Spermatheca and accessory glands. D. Intestinal caeca (ventral margin is on the left).\