Amynthas dilatatus 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 : 7-11

Amynthas dilatatus Qiu and Jiang sp. nov.

( Figure 2 )

Material

Holotype. 1 clitellate (C-HN012-03A): China, Hainan Island, Jianfengling National Nature Reserve (18°43 ′ 26 ″ N, 108°53 ′ 56 ″ E), 900 m elevation, black sandy soil under shrubbery beside road, 4 July 2006, J.X. Li and W.X. Zhang coll.

Paratypes. 1 clitellate (C-HN012-03B) with the same data as for holotype. 7 clitellates (C-HN029-01): China, Hainan Island, Diaoluoshan National Nature Reserve (18°43 ′ 31 ″ N, 109°52 ′ 01 ″ E), 920 m elevation, black sandy soil under meadow, 7 July 2006, J.P. Qiu, M.B. Bouché, J.X. Li and X.L. Zhang colls .

Both clitellates were externally characterized and dissected.

Etymology

The species is named after the characteristics of the seminal chamber.

Diagnosis

Dimensions 120 – 130 mm by 2.9 – 3.2 mm at clitellum, segments 148 – 153. Setae numbering 46 – 50 at III, 56 – 62 at V, 50 – 64 at VIII, 30 – 50 at XX, 41 – 50 at XXV; 0 – 2 between male pores; 22 – 27 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, rounded porophore in a pulvinate pad with three or four circular folds. Spermathecae two pairs in VI – VII, ampulla heart-shaped, duct as long as two-thirds of ampulla. Diverticulum a little longer than the main pouch (duct and ampulla together), seminal chamber swollen.

External characters

Grey dorsal pigment present in the pre-clitellum segments of preserved specimens; light brown pigment on dorsum of the post-clitellum segments; no pigment on ventrum. Dimensions 120 – 130 mm by 2.9 – 3.2 mm at clitellum, segments 148 – 153; the average values of examined individuals: dimensions 125 mm by 3.0 mm at clitellum, segments 150. Prostomium ½ epilobous. First dorsal pore in 11/12. Setae numbering 46 – 50 at III, 56 – 62 at V, 50 – 64 at VIII, 30 – 50 at XX, 41 – 50 at XXV; 0 – 2 between male pores; 22 – 27 between spermathecal pores; setal formula: AA = 1.0 – 1.2AB, ZZ = 1.0 – 1.8ZY. Clitellum annular in XIV – XVI, light brown, swollen; setae invisible externally; gaps in dorsal could be identified clearly.

Spermathecal pores two pairs in 5/6 – 6/7, ventral, eye-like, 0.40 circumference ventrally apart from each other. One or two tiny conical genital papillae before each pore. Three similar presetal genital papillae irregularly present on posterior border of segments VII.

Male pores one pair in XVIII, 0.33 circumference ventrally apart from each other, each on the top of a slightly raised, rounded porophore in a pulvinate pad with three or four circular folds. each male pore is medial to these two tiny papillae ( Figure 2A ), some paratypes with four or five tiny oval genital papillae surrounding each male pore ( Figure 2D ). In holotype, a pair of tiny conical genital papillae present on anterior border of segments XVIII, 0.2 mm apart from each other.

Female pore single in XIV, ovoid, milky white.

Internal characters

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

Ovaries in XIII. Spermathecae two pairs in VI – VII, ampulla heart-shaped, about 1.7 mm long in holotype; ampulla duct slender to stout, as long as two-thirds of ampulla. Diverticulum about 2.2 mm long, slender and short; seminal chamber swollen, about 2.0 mm ( Figure 2B ). No accessory glands observed .

Male sexual system holandric, testis sacs two pairs, in X – XI. Seminal vesicles two pairs, extending in X – XII, the pair in XI larger than the other. Prostate glands developed, inserting in XVIII and extending to 1/2XVII and XX, coarsely lobate composed of three major lobes. Prostatic duct U-shaped, conspicuously curved at the distal part ( Figure 2C ). No accessory glands observed.

Remarks

The present species is obviously different from the other species in Table 3 because of the long diverticulum with a swollen seminal chamber. In addition, A. dilatatus sp. nov. differs from A. tripunctus (Chen 1946) in the features of body length, segment number, setae number between male pores, location of first dorsal pore and prostate glands.

Figures

Figure 2. Amynthas dilatatus 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.