Amynthas marsupiformis Jiang & Yuan, 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 : 274-275

Amynthas marsupiformis Jiang & Yuan , sp. nov.

( Figure 3 )

Holotype. Clitellate specimen (C-GX201314-04A): China, Guangxi Province, Dayao Mountain Nature Reserve (N 23.98077°, E 110.11883°), 907 m a.s.l., yellow sandy topsoil under bush besides road, 15th May, 2013, J. P. Qiu, J. B. Jiang, L. L. Zhang and Y. Dong coll.

Paratypes. 3 clitellate specimens (C-GX201314-04B), same data as for holotype. 2 clitellate (C-GX201318- 02): China, Guangxi Province, Dayao Mountain Nature Reserve (N 24.115622°, E 110.21279°), 1196 m a.s.l., black sandy topsoil besides road in Monkey Mountain , 16th May, 2013, J. P. Qiu, J. B. Jiang, L. L. Zhang and Y. Dong coll.

Etymology. The species is named after the characteristics of the spermathecal diverticulum, its diverticulum is long baggy.

Diagnosis. Dimensions 58–70 mm by 2.4–3.0 mm at clitellum, segments 60–73. Setae numbering 24–28 at III, 34–37 at V, 44–47 at VIII, 35–40 at XX, 36–40 at XXV; 13–16 between spermathecal pores. Spermathecal pores in 6/7–7/8, 0.33 body circumference ventrally apart. Male pores absent. 12 tiny presetal or postsetal genital papillae in parallel rows present on the ventrolateral sides in XVII–XIX. Ampulla ovoid; duct as long as 2.5 ampulla. Diverticulum slightly shorter than main pouch (ampulla and duct), terminal 2/5 dilated into a long marsupial seminal chamber.

External characters. Pinky pigment generally. Dimensions 58–70 mm by 2.4–3.0 mm at clitellum, segments 60–73. Prostomium 1/2 epilobous. First dorsal pore in 12/13. Setae numbering 24–28 at III, 34–37 at V, 44–47 at VIII, 35–40 at XX, 36–40 at XXV; 13–16 between spermathecal pores; setal formula: AA=1.8–2.0AB, ZZ=2.0– 3.0ZY. Clitellum annular in XIV–XVI, light brown, swollen, setae invisible externally. Spermathecal pores two pairs in 6/7–7/8, ventral, eye-like, 0.33 circumference ventrally apart from each other ( Fig. 3A ). No genital papillae observed. Male pores absent. 12 tiny presetal or postsetal genital papillae in parallel rows present on the ventrolateral sides of XVII–XIX ( Fig. 3B ). 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 ball-shaped, in IX–X. Intestine enlarged distinctly from XV. Typhlosole medium from XXVII. Intestinal caeca paired in XXVII, simple, smooth, extending anteriorly to XXIII ( Fig. 3D ). Esophageal hearts in X–XIII. Ovaries in XIII. Spermathecae two pairs in VII and VIII, small, about 1.4–1.6 mm long, ampulla ovoid; duct as long as 2.5 ampulla. Diverticulum slightly shorter than main pouch (ampulla and duct), terminal 2/5 dilated into a long marsupial seminal chamber ( Fig. 3C ). No accessory glands observed. Seminal vesicles two pairs, in XI–XII, very small. No testis sacs, prostate glands, accessory glands and sperm observed.

Remarks. Absence of sperm and main reproductive organs recorded suggest parthenogenesis ( Gates 1972). A. marsupiformis sp. nov. which has no male pores, testis sacs and prostate glands is certainly parthenogenetic. In terms of external characters, A. marsupiformis is very similar to A. axillis ( Chen, 1946) and A. moniliatus ( Chen, 1946) in the characteristics of the post-clitellum papillae. All of them have many small papillae in ventrolateral lines on segments XVII–XIX. Besides, they have similar small body size, reddish or purple pigments, sparse setae and no prostate glands. The main differences of A. marsupiformis from these two species are small seminal vesicles, absence of male pores, testis sacs and accessory glands. In contrast, A. axillis and A. moniliatus have male pores and stalked accessory glands, and their testis sacs and seminal vesicles are developed or well developed. Table 2 lists the differences among them in detail. In addition, A. marsupiformis differs from A. axillis in the features of the first dorsal pore, setal formula and diverticulum. The diverticulum of A. axillis is quite short and bud-like. Besides, A. marsupiformis and A. moniliatus have different setal formula, spermathecal pores, preclitellum papillae, prostatic duct and spermathecae. A. moniliatus , belonging to the sieboldi -group, has 3 pairs of spermathecal pores with many small papillae, S-shaped prostatic duct, stout spermathecal duct and moniliformshaped seminal chamber.

Figures

FIGURE 3. Amynthas marsupiformis Jiang & Yuan, 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).