Amynthas montanus Qiu & Sun, 2012

Sun, Jing, Jiang, Ji-Bao & Qiu, Jiang-Ping, 2012, Four new species of the Amynthas corticis-group (Oligochaeta: Megascolecidae) from Hainan Island, China, Zootaxa 3458, pp. 149-158 : 154-155

Amynthas montanus Qiu & Sun , sp. nov.

( Fig. 2A, B)

Material. Holotype: One clitellate (C-HN032-04) specimen, China, Hainan Province, Mt. Diaoluo (18°40.05’N, 109°53.27’E), 394 m. elevation, cinnamon sandy soil under the banana and arbor forests, 7 Jun. 2006, J. P. Qiu and W. X. Zhang coll. Paratype, One clitellate (C-HN023-02): imcomplete posterior amputee, China, Hainan Province, Mt. Diaoluo (18°43.39’N, 109°51.55’E), 930 m. elevation, yellow cinnamon soil in bamboo and camphor forest beside road, 6 Jun. 2006, J. P. Qiu and M. B. Bouché coll.

Etymology. This species is named after its mountain habitat.

Diagnosis. Bigger-sized Amynthas earthworms; four pairs of spermathecal pores in 5/6–8/9, eye-like, clear, about 0.33 body circumference ventrally apart; male pores 0.33 body circumference ventrally apart, each round, on setal line with elevated center surrounded by 2 to 3 circular folds, with two pairs of ovate and flat-topped genital papillae on 17/18 and 18/19; diverticulum shorter than main spermathecal axis, terminal 0.4 dilated into a rodshaped chamber, stalk composed of entally widening hairpin loops.

Description. External characters. Preserved specimens no pigment, clear mid-dorsal line. Dimensions?– 210mm by 4.5–7.5mm at clitellum, segments?–193, big earthworm, incomplete posterior amputee in paratype; body cylindrical in cross-section, gradually tapered towards head and tail. Prostomium ½ epilobous. Setae numbering 52–74 at III, 72–120 at V, 80–142 at VIII, 52–102 at XX, 60–96 at XXV; 12–18 between male pores; 26–36/VI, 21–42/VII, 24–40/VIII between spermathecal pores, setal formula AA=1.2–1.8AB, ZZ=1.8–2ZY. Clitellum annular XIV–XVI, smooth, light-red, or light brown; setae can be seen externally in XIV–XVI; dorsal pore present; one specimen has furrows in clitellum.

First dorsal pore 12/13. Four pairs of spermathecal pores in 5/6–8/9, about 0.33 circumference ventrally apart. Male pores paired in XVIII, 0.33 body circumference ventrally apart; each round on setal line with elevated center surrounded by 2 to 3 circular folds. Genital papillae ovate, flat-topped, diameter 0.7–0.8mm, surrounded by epidermal folds, paired on 17/18, 18/19 median to male pores. ( Fig. 2A). Female pore single mid-ventral in XIV.

Internal characters. Septa 5/6–7/8 and 10/11–12/13 muscular, 13/14 slightly thickened, 8/9–9/10 absent.

Dorsal blood vessel single, continuous onto pharynx; esophageal hearts enlarged in X–XIII. Gizzard in VIII–X, ball-shaped; intestine enlarged gradually from XVI; intestinal caeca simple, originating in XXVII and extending forward to XXV, finger-shaped sac with smooth margins.

Ovaries in XIII. Spermathecae paired in VI–IX, about 4.2mm long; ampulla heart-shaped, stout duct as long as 0.75 ampulla; diverticulum shorter than main spermathecal axis, terminal 0.4 dilated into a rod-shaped chamber, stalk composed of entally widening hairpin loops; no nephridia on spermathecal ducts ( Fig. 2B). Male sexual system holandric, testis sacs two pairs, ventral in X, XI, anterior pair connected with membrane on ventrum between left and right side; seminal vesicles paired in each of XI and XII, anterior pair bigger in size, the latter pair vestigial; prostates in XVI–XX, coarsely lobate, prostatic duct u-shaped, distal end appreciably enlarged. No accessory glands were seen.

Remarks. Amynthas montanus sp. nov. is a big octothecal earthworm belonging to the corticis -group ( Sims & Easton, 1972). The arrangement of male pore region genital papillae of Amynthas montanus sp. nov. is somewhat similar to that of Amynthas tetrapapillatus Quan 1989 from Hainan Island, Amynthas diaoluomontis Qiu and Sun 2009 from Hainan Island and Amynthas wulinensis Tsai 2001 from Taiwan. Table 2 is given to illustrate the differences between Amynthas montanus sp. nov. and those three reported species in detail.

This new species differs from A. tetrapapillatus in the features of pigment, position of first dorsal pore, setae in clitellum, transverse distance between spermathecal pores, number and size of spermathecae. Amynthas montanus sp. nov. has no pigment, first dorsal pore in 12/13, setae externally in XIV–XVI, 0.33 circumference ventrally apart between spermathecal pores and four pairs of spermathecae which are 4.2mm long. In contrast, A. tetrapapillatus has light maroon pigment, first dorsal pore in 11/12, no setae externally in XIV–XVI, spermathecal pores 0.17 circumference dorsally apart and only one pair of spermathecae which is 1.8–2.0mm long.

Amynthas montanus sp. nov. is easily distinguished from A. diaoluomontis by the number of spermathecae, transverse distance between spermathecal pores, prostomium, setal formula, characters of male pores, indentations of intestinal caeca, the size of spermathecae and characters of diverticulum.

Amynthas montanus sp. nov. and A. wulinensis can be separated on the basis of its variable position of genital papillae from XVII–XX and the character of diverticulum. The genital papillae of A. wulinensis are usually located in posterior annulet between the setal line and the posterior intersegmental furrow, while there may occasionally be an additional pair or 1 papilla in XX, or missing one in XVII or XIX. In Amynthas montanus sp. nov., genital papillae are always situated on 17/18, 18/19 median to the male pores. The diverticulum of A. wulinensis has an oval, shining white seminal chamber and a slender, straight stalk, other than a rod-shaped chamber and hairpin looped stalk. Otherwise, they have some other differences in the position of first dorsal pore, setae and dorsal pore of clitellum, transverse distance of spermathecal pores, pigment, characters of gizzard and accessory glands near prostates.