Amynthas anteporus Jiang & Dong, 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 : 271-272

Amynthas anteporus Jiang & Dong , sp. nov.

( Figure 2 )

Holotype. Clitellate specimen (C-GX201305-01A): 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.

Paratypes. 2 clitellate specimens (C-GX201305-01B), same data as for holotype.

Etymology. The species is named after the characteristics of first dorsal pore.

Diagnosis. Dimensions 30–47 mm by 1.8–2.0 mm at clitellum, segments 66–73. Setae numbering 40–43 at III, 42–46 at V, 40–46 at VIII, 34–37 at XX, 36–38 at XXV; 8–11 between male pores, 8–9 between spermathecal pores. Spermathecal pores two pairs in 6/7–7/8, 0.25 circumference ventrally apart from each other. Male pores one pair in XVIII, 0.33 circumference ventrally apart from each other, each on top of a small, round porophore. Ampulla longitudinal oval; slender duct as long as ampulla. Diverticulum slightly shorter than main pouch, terminal 2/5 dilated into a long claval seminal chamber. Prostate glands undeveloped. No prostate glands observed.

External characters. No pigment on dorsum and ventrum. Dimensions 30–47 mm by 1.8–2.0 mm at clitellum, segments 66–73. Prostomium 1/2 epilobous. First dorsal pore in 5/6. Setae numbering 40–43 at III, 42–46 at V, 40–46 at VIII, 34–37 at XX, 36–38 at XXV; 8–11 between male pores, 9–11 between spermathecal pores; setal formula: AA=1.6–3.0AB, ZZ=1.8–2.0ZY. Clitellum annular, no pigment, in XIV–XVI, setae invisible externally. Spermathecal pores two pairs in 6/7–7/8, ventral, very small, about 0.25 circumference ventrally apart from each other ( Fig. 2A ). Male pores one pair in XVIII, 0.33 circumference ventrally apart from each other, each on the top of a small, slightly raised, round porophore ( Fig. 2B ). No genital papillae observed. Female pore single in XIV, milk-white, ovoid.

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, simple, smooth, extending anteriorly to XXIII ( Fig. 2D ). Esophageal hearts in X– XIII. Ovaries in XIII. Spermathecae two pairs in VII and VIII, 0.9–1.0 mm long, ampulla longitudinal oval; slender duct as long as ampulla. Diverticulum a little shorter than main pouch (ampulla and duct), terminal 2/5 dilated into a swollen, long claval seminal chamber ( Fig. 2C ). No accessory glands observed. Holandric: Testis sacs two pairs, in X–XI, tiny. Seminal vesicles two pairs, very small, in XI–XII. Prostate glands undeveloped, inserting in XVIII and extending from XVII to XIX, prostatic duct U-curved, slightly thicker at the distal part. No accessory glands and sperm observed.

Remarks. The tiny testis sacs, small seminal vesicles and undeveloped prostate glands of Amynthas anteporus may be due to parthenogenetic degradation. Among species of the tokioensis -group, A. anteporus sp. nov. resembles A. vividus ( Chen, 1946) , A. zhongi Qiu & Wang, 1991 and A. heshanensis Zhang & Li, 2006 in the characteristics of the male pores ( Table 1). The new species can be separated from the other three species on the basis of body size, segment number, pigment, first dorsal pore position, clitellum, testis sacs, seminal vesicles, prostate glands and spermathecae. A. anteporus sp. nov. is a small earthworm, 30–47 mm in length; its first dorsal pore is in 5/6, and the clitellum is in XIII–1/2XVII; testis sacs and seminal vesicles are very small; prostate glands are not developed. A. zhongi has similar body size, testis sacs and seminal vesicles, nevertheless its first dorsal pore is in 11/12, clitellum is in XIV–XVI, and prostate glands are developed. A. vividus and A. heshanensis are both longer than A. anteporus , and their seminal vesicles and prostate glands are developed too. Moreover, A. vividus and A. zhongi have an elongate spermathecal duct with unmarked seminal chamber; A. heshanensis has a very short spermathecal duct and a curved seminal chamber, while the slender duct in A. anteporus is as long as the ampulla, and the seminal chamber is swollen.

Figures

FIGURE 2. Amynthas anteporus Jiang & Dong, sp. nov. A. Region of spermathecal pores, ventral view. B. Region of male pores, ventral view. C. Spermatheca. D. Intestinal caeca (ventral margin is on the left).