Amynthas crassitubus Qiu & Dong, 2018

Dong, Yan, Yuan, Zhu, Jiang, Jibao, Zhao, Qi & Qiu, Jiangping, 2018, Two new species of earthworms belonging to the genus Amynthas (Oligochaeta: Megascolecidae) from Guangxi Province, China, Zootaxa 4496 (1), pp. 259-268 : 260-263

Amynthas crassitubus Qiu & Dong , sp. nov.

( Figure 1 , Table 2)

Material. Holotype. Clitellate specimen (C-GX201302-13A), China, Guangxi Province , Shiwan Mountain Nature Reserve , N 21.50594°, E 107.54579°, 242 m asl, black soil under bryophytes in subtropical evergreen forest, 12th May, 2013, J. P. Qiu, Y, Hong, J. B. Jiang, L. L. Zhang and Y. Dong coll. Paratypes. 6 clitellate specimens C- GX201302-13B, same date as for holotype. 1 clitellate specimen C-GX201302-09, same date as for holotype. 1 clitellate specimen, C-GX201303-02, China, Guangxi Province , Shiwan Mountain Nature Reserve, N 21.50527°, E 107.54595°, 290 m asl, other data same as for holotype.

Etymology. The species is named after its stout diverticulum of spermathecae.

Diagnosis. Dimensions 78–130 mm by 4.2–4.5 mm at clitellum, segments 70–130. First dorsal pore in 12/13. Setae numbering 27–32 at?, 32–42 at?, 41–48 at?, 46–50 at XX, 60–62 at XXV; 12 between male pores; 20–22 at VII, 22–24 at? between spermathecal pores. Spermathecal pores three pairs in 6/7–8/9, 0.4 circumference ventrally apart from each other ( Fig. 1A ). Male pores one pair in XVIII, 0.4 circumference apart ventrally, each on the top of a middle, round porophore ( Fig. 1C ). Ampulla long-oval; stout duct extremely short. Diverticulum about 1.5 mm long, terminal 1/5 dilated into a ball-shaped seminal chamber ( Fig. 1B ). Prostate glands well-developed ( Fig. 1D ). No accessory glands observed.

Description. External characters. Pigment from fuchsia to light yellowish brown on dorsum, no pigment on ventrum, clitellum light yellowish brown. Dimensions 7.8–130 mm by 4.2–4.5 mm at clitellum, segments 70–130. Prostomium 1/2 epilobous. First dorsal pore in 12/13. Setae numbering 27–32 at?, 32–42 at?, 41–48 at?, 46–50 at XX, 60–62 at XXV; 12 between male pores; 20–22 at VII, 22–24 at? between spermathecal pores. Setae formula: AA=1.4–2.2AB, ZZ=1.0–2.0ZY. Clitellum annular, rough, in XIV–XVI, dense setae on ventral middle line. Spermathecal pores three pairs in 6/7–8/9, eye-like, 0.4 circumference ventrally apart from each other. Three or four postsetal elliptic genital papillae, flat-topped and collapsed in the middle, present on VIII and IX, about 0.4 circumference apart ventrally. Male pores one pair in XVIII, 0.4 circumference apart ventrally, each on the top of a middle, round porophore surrounded by 3–4 circular ridges, with two presetal genital papillae on ventrum of XVIII and XIX, some specimens with an additional papilla on right ventrum of XX. Female pore single in XIV, grey, ovoid.

Internal characters. Septa 5/6– 7/8, 10/11–13/14 thick, 8/9–9/10 absent. Gizzard bucket-shaped, in IX–X. Intestine enlarged distinctly from XIV. Intestinal caeca paired in XXVII, simple, smooth, extending anteriorly to XXIII. Esophageal hearts four pairs in X–XIII, developed. Ovaries in IX. Spermathecae three pairs in VII–IX, small, about 1.6–3.8 mm long, the first pair is larger than the last two pairs. Ampulla spherical-shaped; duct extremely short. Diverticulum about 1.5 mm, terminal 1/5 dilated into ball-shaped seminal chamber ( Fig. 1B ). No accessory glands observed. Holandric: Testis sacs two pairs, in X–XI, developed. Seminal vesicles two pairs, in XI–XII, developed. Prostate glands well-developed, inserting in XVIII, and extending from 1/2XVI to 1/2XX, prostate duct twist at frontend, dilated at the middle part. No accessory glands observed.

Remarks. Amynthas crassitubus sp. nov. from Shiwan Mountain National Nature Reserve belongs to the sieboldi -group in Sims and Easton (1972). It is similar to Amynthas taipeiensi s ( Tsai, 1964), Amynthas leucocircus ( Chen, 1933) , and Amynthas szechuanensis ( Chen, 1931) from China. Those four species share the following character combination: 3 pairs of spermathecal pores intersegmental in 6/7–8/9, papillae observed on postclitellum, short ampullar duct, developed seminal vesicles and prostate glands. Table 2 gives details of the differences among these species.

Amynthas taipeiensis ( Tsai, 1964) differs from the new species in green pigment on dorsum, wider distance between spermathecal and male pores, fewer papillae in the spermathecal pore region and zigzagged or coiled diverticulum stalk. Amynthas leucocircus ( Chen, 1933) differs from Amynthas crassitubus in larger body size, and presence of accessory glands in the regions of spermathecae and prostate glands. Amynthas szechuanensis ( Chen, 1931) differs in four further characters from the new species: no papilla observed in preclitellar region, the number and position of papillae in male pore region are more numerous and complex, but accessory glands appear in both regions; besides, its intestinal caeca are between simple and complex.

Figures

FIGURE 1. Amynthas crassitubus sp. nov. A. External ventral view of segments VI–X showing intersegmental spermathecal pores at 6/7–8/9 and 4 postsetal elliptic genital papillae. B. Spermatheca. C. External ventral view of segments XVII–XIX with male pores in XVIII and 5 presetal papillae. D. Prostate.