Amynthas infuscuatus Jiang and Sun, 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 : 11-13

Amynthas infuscuatus Jiang and Sun sp. nov.

( Figure 3 )

Material

Holotype. 1 clitellate (C-HN020-02A): China, Hainan Island, Jianfengling National Nature Reserve (18°44 ′ 45 ″ N, 108°50 ′ 32 ″ E), 1020 m elevation, cinnamon soil under tropical rainforest vegetation, 5 July 2006, J.P. Qiu, M.B. Bouché, J.X. Li and X.L. Zhang colls.

Paratypes. 2 clitellates (C-HN020-02B) with the same data as for holotype.

All three clitellates were externally characterized and dissected.

Etymology

The species is named after its dark pigment.

Diagnosis

Dimensions 60 – 78 mm by 1.4 – 1.6 mm at clitellum, segments 130 – 139. Setae numbering 46 – 48 at III, 56 – 60 at V, 49 – 52 at VIII, 42 – 46 at XX, 44 – 48 at XXV, 8 – 10 between male pores. Spermathecal pores two pairs in 5/6 – 6/7, 0.33 circumference ventrally apart from each other. 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 four circular folds. Spermathecae two pairs in VI – VII, ampulla ovoid, duct twice as long as ampulla. Diverticulum slightly longer than main pouch, slender, terminal one-third dilated into a swollen chamber.

External characters

Purple dorsal pigment before segment VIII of preserved specimens; light brown pigment on dorsum after segment VIII, no pigment on ventrum. Dimensions 60 – 78 mm by 1.4 – 1.6 mm at clitellum, segments 130 – 139; the average values of examined individuals: dimensions 68 mm by 1.5 mm at clitellum, segments 134. Prostomium ½ epilobous. First dorsal pore in 12/13. Setae numbering 46 – 48 at III, 56 – 60 at V, 49 – 52 at VIII, 42 – 46 at XX, 44 – 48 at XXV; 8 – 10 between male pores; setal formula: AA = 1.0 – 1.2AB, ZZ = 1.0 – 1.2ZY. Clitellum annular, orange colour, in XIV – XVI, setae visible externally.

Spermathecal pores two pairs in 5/6 – 6/7, ventral, eye-like, 0.33 circumference ventrally apart from each other.

Male pores one pair in XVIII, 0.33 circumference ventrally apart from each other, each on the top of a slightly raised, oval porophore in a pulvinate pad with three or four circular folds. Two rounded genital papillae, flat-topped, present at inner ridge of porophore, anteromedial one larger than the other ( Figure 3A ).

Female pore single in XIV, oval.

Internal characters

Septa 6/7 – 7/8 thick and muscular, 10/11 – 12/13 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, brown, extending anteriorly about to XXIV. Oesophageal hearts in X – XIII.

Ovaries in XIII. Spermathecae two pairs in VI – VII, ampulla ovoid, about 2.5 mm long in holotype; duct slender, twice as long as ampulla. Diverticulum slightly longer than main pouch, slender, terminal one-third dilated into a swollen chamber ( Figure 3B ), milky white. No accessory glands observed .

Male sexual system holandric, testis sacs two pairs, in X – XI. Seminal vesicles two pairs, extending in X – XII, the anterior pair larger. Testis sacs and seminal vesicles separated from each other on ventrum. Prostate glands developed, inserting in XVIII and extending to XVI and half of XX, coarsely lobate composed of two major lobes. Prostatic duct U-shaped, slender ( Figure 3C ). No accessory glands observed.

Remarks

Both A. infuscuatus sp. nov. and A. tripunctus have similar body length, setae, location of first dorsal pore, seminal vesicles and diverticulum length. However, A. infuscuatus sp. nov. is distinguished from A. tripunctus by its segment number, ampulla shape and seminal chamber length.

In comparison to A. incongruus , spermathecae of A. infuscuatus sp. nov. is quite different. Ampulla is heart-shaped, duct slightly shorter than ampulla, and terminal two-sevenths of diverticulum dilated into a swollen seminal chamber. Moreover, body length and first dorsal pore are also distinctive characters.

Although both have terminal third dilated into seminal chamber, A. infuscuatus sp. nov. and A. instabilis have no similar spermathecae. The ampulla of A. infuscuatus is ovoid, smaller than the heart-shaped ampulla of A. instabilis , but its ampulla duct and diverticulum are longer.

Figures

Figure 3. Amynthas infuscuatus Jiang and Sun sp. nov. (A) Ventral view of holotype, scale bar 2 mm; (B) spermathecae of holotype, scale bar 1 mm; (C) prostate gland of holotype.