Amynthas instabilis Qiu and Jiang, 2014

Jiang, Jibao, Sun, Jing, Zhao, Qi & Qiu, Jiangping, 2014, Four new earthworm species of the genus Amynthas Kinberg (Oligochaeta: Megascolecidae) from the island of Hainan and Guangdong Province, China, Journal of Natural History 49 (1), pp. 1-17 : 3-7

Amynthas instabilis Qiu and Jiang sp. nov.

( Figure 1 )

Material

Holotype. 1 clitellate (C-HN011-02A): China, Hainan Island, Jianfengling National Nature Reserve (18°43 ′ 32 ″ N, 108°53 ′ 33 ″ E), 860 m elevation, black sandy soil under shrubbery beside road, 4 July 2006, J.X. Li and W.X. Zhang coll.

Paratypes. 60 clitellates (C-HN011-02B) and 3 clitellates (C-HN011-03)with the same data as for holotype; 1 clitellate (C-HN014-03): China, Hainan Island, Jianfengling National Nature Reserve (18°43 ′ 58 ″ N, 108°53 ′ 10 ″ E), 890 m elevation, sandy soil under evergreen forest, 4 July 2006 , J.P. Qiu and M.B. Bouché colls; 8 clitellates (C-HN015-01): China, Hainan Island, Jianfengling National Nature Reserve (18°43 ′ 56 ″ N, 108°53 ′ 13 ″ E), 895 m elevation, cinnamon soil under tropical rainforest vegetation, 4 July 2006 , J.P. Qiu, M.B. Bouché and X.L. Zhang colls. 2 clitellates (C-HN201001-01): China, Hainan Island, Diaoluoshan National Nature Reserve (18°42 ′ 32 ″ N, 109°50 ′ 25 ″ E), 631 m elevation, black sandy soil under arbor vegetation, 23 July 2010, J.B. Jiang and Y.Z. Guo coll. 1 clitellate (C-HN201101-03): China, Hainan Island, Diaoluoshan National Nature Reserve (18°44 ′ 18 ″ N, 108°52 ′ 01 ″ E), 840 m elevation, yellow soil under broadleaved evergreen forest, 23 May 2011, J.P. Qiu, J.B. Jiang, Q. Zhao, D. Cluzeau and W.K. Zhang coll. 2 clitellates (C-GD201105-03): China, Guangdong Province, Xiangtoushan National Nature Reserve (23°15 ′ 38 ″ N, 114°22 ′ 31 ″ E), 360 m elevation, yellow soil under broadleaved evergreen forest, 23 October 2011, J.B. Jiang, J. Sun, J.X. Li and X.D. Lei coll.

Ten individuals were dissected and 13 were characterized externally only.

Etymology

The species is named after its characteristic of variable numbers of genital papillae in the male pore region.

Diagnosis

Dimensions 74 – 125 mm by 2.9 – 4.0 mm at clitellum, segments 82 – 145. Setae numbering 30 – 54 at III, 42 – 64 at V, 52 – 62 at VIII, 40 – 52 at XX, 40 – 56 at XXV; 0 – 2 between male pores; 15 – 22 between spermathecal pores. Spermathecal pores in 5/6 – 6/7, 0.40 body circumference ventrally apart. Male pores in XVIII, 0.33 body circumference ventrally apart, each on the top of a slightly raised, oval porophore in a pulvinate pad with three to six circular folds. Spermathecae two pairs in VI – VII, ampulla heartshaped, duct as long as ampulla. Diverticulum half as long as main pouch (duct and ampulla together), terminal one-third dilated into an ovoid chamber.

External characters

Taupe dorsal pigment, ventral pigment lighter present in the pre-clitellum segments of preserved specimens; tan pigment on dorsum, no pigment on ventrum of the postclitellum segments. Dimensions 74 – 125 mm by 2.9 – 4.0 mm at clitellum, segments 82 – 145; the average values of examined individuals: dimensions 104 mm by 3.3 mm at clitellum, segments 128. Secondary annulations conspicuous in segments XVII – XVIII. Prostomium ½ epilobous. First dorsal pore of all examined individuals in 11/12. Setae numbering 30 – 54 at III, 42 – 64 at V, 52 – 62 at VIII, 40 – 52 at XX, 40 – 56 at XXV; 0 – 2 between male pores; 15 – 22 between spermathecal pores; setal formula: AA = 1.0 – 1.3AB, ZZ = 1.0 – 2.0ZY. Clitellum annular, pinkish or brown, in XIV – XVI, setae invisible externally.

Spermathecal pores two pairs in 5/6 – 6/7, ventral, eye-like, sometime invisible, milky white porophore in centre, 0.40 circumference ventrally apart from each other. A tiny conical genital papilla before each pore. A similar postsetal genital papilla on midventral line of segment VI, and a pair of presetal genital papillae, 0.2 mm apart from each other, on the anterior border of segment VII.

Male pores one pair in XVIII, 0.33 circumference apart ventrally, each on the top of a slightly raised, oval porophore in a pulvinate pad with six circular folds, some paratypes with three circular folds. Two tiny oval genital papillae, present at anterior and posterior of porophore, each male pore is medial to these two tiny papillae ( Figure 1A ); some paratypes with three tiny oval genital papillae surrounding left male pore ( Figure 1D ). Genital papillae numbers in male pores region are variable among specimens.

Female pore single in XIV, rounded, milky white.

Internal characters

Septa 4/5 – 6/7, 10/11 thick and muscular, 11/12 slightly thickened, 8/9 – 9/10 absent. Gizzard long bucket-shaped, in IX – X. Intestine enlarged distinctly from XVI. Intestinal caeca paired in XXVII, simple, smooth, with a slight indentation on terminal dorsal margin, extending anteriorly to XXIV. Oesophageal hearts in X – XIII.

Ovaries in XIII. Spermathecae two pairs in VI – VII, ampulla heart-shaped, about 2.3 mm long in holotype; ampulla duct slender to stout, as long as ampulla. Diverticulum as long as a half main pouch (duct and ampulla together), slender, terminal one-third dilated into an ovoid chamber ( Figure 1B ), milky white. No accessory glands observed.

Male sexual system holandric, testis sacs two pairs, in X – XI. Seminal vesicles two pairs, extending in XI – XIII, the posterior pair larger than the anterior one and extending to XIII. Prostate glands developed, inserting in XVIII and extending to XVII and XX, coarsely lobate, prostatic duct U-shaped, slightly thicker at the distal part ( Figure 1C ). No accessory glands observed.

Remarks

In comparison to the other 30 species of the morrisi -group reported from China (19) and other Asian countries (11), Amynthas instabilis sp. nov. is closely related to Amynthas incongruus (Chen 1933) and Amynthas tripunctus (Chen 1946) from China, and to A. dilatatus sp. nov., A. infuscuatus sp. nov. and A. qiongzhongensis sp. nov. These six species share some similarities with similar male pores and genital markings, two pairs of intersegmental spermathecal pores in 5/6 – 6/7, and simple intestinal caeca. Table 3 illustrates in detail the differences among A. incongruus (Chen 1933) , A. tripunctus (Chen 1946) and the four new species.

Amynthas instabilis sp. nov. differs from A. tripunctus (Chen 1946) by the presence of pigment on the dorsum, location of first dorsal pore, setae number in segment VIII, prostate glands and spermathecal characters. Amynthas instabilis sp. nov. has tan pigment on the dorsum, first dorsal pore in 11/12, setal number 52 – 62 at VIII, prostates glands less developed and diverticulum half as long as main pouch. In contrast, A. tripunctus has grey pigment on dorsum, first dorsal pore in 12/13, setae number fewer at VIII, more setae between male pores, well-developed prostate glands and a longer diverticulum.

Amynthas instabilis sp. nov. and A. incongruus (Chen 1933) can be separated on the basis of spermathecal characters. The ampulla of A. instabilis sp. nov. is heartshaped, a slender to stout duct is as long as ampulla. The ampulla of A. incongruus is ovoid or elongate spherical, duct either long and slender, or short stout, terminal three-quarters of diverticulum dilated into a twist chamber. In addition, A. incongruus has very small seminal vesicles and accessory glands, with prostate glands absent entirely and in a few cases well developed (Chen 1933).

Figures

Figure 1. Amynthas instabilis Qiu and Jiang sp. nov. (A) Ventral view of holotype, scale bar 2 mm; (B) spermathecae of holotype, scale bar 1 mm; (C) prostate gland of holotype; (D) male pore region of one paratype.