Amynthas stabilis Dong & Jiang, 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 : 263-266

Amynthas stabilis Dong & Jiang , sp. nov.

( Figure 2 , Table 3)

Material. Holotype. Clitellate specimen (C-GX201305-06A), China, Guangxi Province, Shiwan Mountain Nature Reserve, N 21.50396°, E 107.53350°, 494 m asl, red sandy soil under bryophytes besides road, 13th May, 2013, J. P. Qiu, Y, Hong, J. B. Jiang, L. L. Zhang and Y. Dong coll. Paratypes. 4 clitellate specimens, C-GX201305-06B, same date as for holotype.

Etymology. The species is named after its stable number, location and size of genital papillae in spermathecal pore and male pore region.

Diagnosis. Dimensions 61–68 mm by 3.0– 3.2 mm at clitellum, segments 87–103. First dorsal pore in 12/13. Setae numbering 10–14 at?, 17–20 at?, 23–26 at?, 36–38 at XX, 32–38 at XXV; 6–8 between male pores; 6–8 at VII, 6 at? between spermathecal pores. Spermathecal pores three pairs in 6/7–8/9. Four presetal genital papillae in VIII and IX, 0.25 circumference ventrally apart from each other ( Fig. 2A ). Male pores one pair in XVIII, 0.33 circumference apart ventrally, each on the top of an elliptic porophore surrounded by 1–2 circular ridges, with four big intersegmental genital papillae at 17/18 and 18/19, flat-topped and collapsed in the middle, 0.25 circumference apart ventrally ( Fig. 2B ). Ampulla elongate, oval-shaped, stout duct, as long as 1/2 ampulla. Diverticulum slightly shorter than main pouch, terminal 1/4 dilated into a club-shaped seminal chamber ( Fig. 2C ). Prostate glands welldeveloped ( Fig. 2D ). No accessory glands observed in male pore region.

External characters. Tan pigment on middle dorsum of the whole body, no pigment on ventral and lateral sides. Dimensions 61–68 mm by 3.0– 3.2 mm at clitellum, segments 87–103. Prostomium 1/2 epilobous. First dorsal pore in 12/13. Setae numbering 10–14 at?, 17–20 at?, 23–26 at?, 36–38 at XX, 32–38 at XXV; 6–8 between male pores; 6–8 at VII, 6 at? between spermathecal pores. Setae formula: AA=1.4–2.2AB, ZZ=3.6–4.0ZY. Clitellum annular, in XIV–XVI, setae invisible externally. Spermathecal pores three pairs in 6/7–8/ 9, small. Four presetal genital papillae observed in VIII and IX, 0.33 circumference ventrally apart from each other. Male pores one pair in XVIII, 0.33 circumference apart ventrally, each on the top of an elliptic porophore surrounded by 1–2 circular ridges, with four big intersegmental collapse-topped genital papillae between XVII–XIX, 0.33 circumference apart ventrally. Female pore single in XIV.

Internal characters. Septa 5/6–7/8 thick, 10/11–13/14 slightly thickened, 8/9–9/10 absent. Gizzard bucketshaped, in IX–XI. Intestine enlarged distinctly from XV. Intestinal caeca paired in XXVII, simple, smooth, extending anteriorly to XXII. Esophageal hearts in X–XIII, the first pair tiny, the last three pairs developed. Ovaries in IX. Spermathecae three pairs in VII–IX, small, about 1.5 mm long. Ampulla long oval-shaped, stout duct as long as 1/2 ampulla. Diverticulum a little shorter than main pouch (ampulla and duct), terminal 1/4 dilated into a club-shaped seminal chamber ( Figure 2B ). One nubbly accessory gland observed near the distal part of the last two pair spermathecal duct. Holandric: Testis sacs two pairs, in X–XI, well-developed. Seminal vesicles two pairs, in XI–XII. Prostate glands well-developed, inserting in XVIII and extending from 1/2XV to XX, nubbly lobate, prostate duct U-shaped, slightly thicker at the distal part. No accessory glands observed in male pore region.

Remarks. Amynthas stabilis sp. nov. is somewhat similar to Amynthas nubilus ( Chen, 1946) , Amynthas dactilicus ( Chen, 1946) , Amynthas hupeiensis (Michaelsen, 1895) ( Chang et al. 2009) and Amynthas dongyinensis Shen, 2014 considering body size, segment number, distance of spermathecal and male pores and intestinal caeca. These species all belong to the sieboldi -group ( Sims & Easton 1972). An in-depth comparison table is shown to illustrate more clearly the distinct characters of these four species (Table 3).

TABLE ³. A comparison of characters of Amynthas stabilis sp. nov., A. nubilus ( Chen, 1946) , A. dactilicus ( Chen, 1946) , A. hupeiensis (Michaelsen, 1895) anđ A. dongyinensis 4hen, 2014. 565

7 character unknown.

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TABLE ³. (Continueđ)

Amynthas stabilis sp. nov. is easily distinguished from Amynthas nubilus ( Chen, 1946) and Amynthas dactilicus ( Chen, 1946) by its darker body pigment and intersegmental collapse-topped papillae in male pore region. In addition, in Amynthas dactilicus ( Chen, 1946) , a spermathecal diverticulum is absent, and there are no preclitellar papillae. Amynthas stabilis is similar to Amynthas hupeiensis (Michaelsen, 1895) with respect to intersegmental collapse-topped papillae in male pore region. However, Amynthas hupeiensis differs from the new species in dark-green body pigment, absence of preclitellar papilla and accessory glands, while its slender spermathecal diverticulum is longer than twice the length of the spermatheca. Amynthas dongyinensis Shen, 2014 differs from the new species in higher setae number (up to 57), absence of papillae near spermathecal pore and male pore, and in the spermathecal diverticulum which is longer than the main pouch.

Figures

FIGURE 2. Amynthas stabilis sp. nov. A. External ventral of segments VI–VIII with intersegmental spermathecal pores at 6/ 7–8/9 and 4 presetal genital papillae in VIII and IX. B. Spermatheca. C. Ventral view of segments XVII–XIX showing male pores and 4 intersegmental genital papillae. D. Prostate.