Amynthas stricosus 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 : 150-151

Amynthas stricosus Qiu & Sun , sp. nov.

( Fig. 1A, B)

Material. Holotype: One clitellate (C-HN029-02A) specimen, China, Hainan Province, Mt. Diaoluo (18°43.31’N, 109°52.01’E), 920 m. elevation, dark cinnamon soil under meadow vegetation, 7 Jun. 2006, J. P. Qiu, J. X. Li and M. B. Bouché coll. Paratypes: Two clitellates (C-HN027-02 and C-HN027-04), 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. One clitellate (C-HN028-06), China, Hainan Province, Mt. Diaoluo (18°43.45’N, 109°51.50’E), 1008 m. elevation, brown soil under a dead and lying tree, 6 Jun. 2006, J. P. Qiu and W. X. Zhang coll. Six clitellates (C-HN030-02), China, Hainan Province, Mt. Diaoluo (18°43.28’N, 109°52.01’E), 925 m. elevation, yellow cinnamon soil under meadow vegetation near a pond, 7 Jun. 2006, J. P. Qiu, J. X. Li and M. B. Bouché coll. Other material: four clitellates and four semiclitellates (C-HN029-02B), same data as for holotype.

Etymology. This species is named after its lack of pigmentation.

Diagnosis. Medium-sized Amynthas earthworms; no pigment; four pairs of spermathecal pores in 5/6–8/9, 0.4 circumference ventrally apart; male pores 0.33 body circumference ventrally apart, each on a coniform glandular disc surrounded by a round pad, with single or paired postsetal genital papillae in XVII, XIX and XX; diverticulum as long as main spermathecal axis, terminal 0.4 dilated into a band-shaped chamber.

Description. External characters. Preserved specimens no pigment, unclear mid-dorsal line. Dimensions 72–97mm by 2–2.8mm at clitellum, segments 116–142; body cylindrical in cross-section, gradually tapered towards head and tail. Prostomium ½ epilobous. Setae numbering 30–54 at III, 50–76 at V, 62–72 at VIII, 40–70 at XX, 38–52 at XXV; 10–12 between male pores; 22–28/VI, 22–30/VII, 23–29/VIII between spermathecal pores, setal formula AA=1.1–1.2AB, ZZ=1.2–2ZY. Clitellum annular XIV–XVI, greyish-white, or reddish-brown, or light brown; setae can be seen externally in XIV–XVI; dorsal pore present or absent; some have furrows in clitellum.

First dorsal pore 11/12 or 12/13. Four pairs of spermathecal pores in 5/6–8/9, 0.4 circumference ventrally apart. Male pores paired in XVIII, 0.33 body circumference ventrally apart; each on a coniform glandular disc surrounded by a round pad. Genital papillae postsetal, single or paired in XVII, XIX and XX; number and segments variable among the 10 specimens of the type-series, in XVII in 8 specimens, paired in 7, unpaired to the right in 1 specimen; in XIX in 9 specimens, paired in 7, unpaired to the right in 2 specimens; in XX in 7 specimens, paired in 6, unpaired to the right in 1 specimen. Each papilla small, round, slightly convex ( Fig. 1A). Female pore single mid-ventral in XIV.

Internal characters. Septa 6/7–7/8 thick and muscular, 10/11–13/14 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 and distinctly from XXI; intestinal caeca simple, originating in XXVII and extending forward to XXIV, horn-shaped sac with smooth margins.

Ovaries in XIII. Spermathecae paired in VI–IX, about 1.6mm long; ampulla heart-shaped, gradually slender duct as long as ampulla; diverticulum as long as main spermathecal axis, slender, terminal 0.4 dilated into a bandshaped chamber; no nephridia on spermathecal ducts ( Fig. 1B). Male sexual system holandric, testis sacs two pairs, ventral in X, XI, anterior pair bigger in size, which is in close proximity to two sides on dorsum; seminal vesicles paired in each of XI and XII, anterior pair bigger in size and connected with membrane on dorsum, the latter pair separated from each other but closer; prostates in XVI–XX, coarsely lobate, prostatic duct s-shaped, distal end appreciably enlarged. No accessory glands were seen.

Remarks. Amynthas stricosus sp. nov. keys to the corticis -group in Sims and Easton (1972) with four pairs of spermathecal pores intersegmental in 5/6–8/9. This present species is similar to Amynthas homosetus ( Chen, 1938) in the locality and number of spermathecal pores, heart-shaped ampulla and developed prostate glands. However, the new species can be distinguished from A. homosetus in that it lacks pigment, has a smaller body size, setae visible externally in XIV–XVI, two male pores more widely spaced, variable numbers of genital papillae near male pores, and a longer band-shaped diverticulum chamber. Amynthas homosetus , on the other hand, has dark chocolate pigment on anterior dorsum and grey on other parts of body, body size rather bigger, setae visible ventrally just in XVI, 0.25 of circumference ventrally separated male pores, no genital papillae near male pores, and a shorter diverticulum with an ovoid seminal chamber.

Additionally, this new species resembles Amynthas saccatus Qiu and Wang, 1993 in the genital papillae of male pore region, but can be distinguished from the latter in many essential characters. Firstly, there are 3 pairs of intersegmental spermathecal pores in 6/7–8/ 9 in A. saccatus , but 4 pairs of spermathecal pores in 5/6–8/ 9 in A. stricosus sp. nov.. Secondly, each male pore of A. saccatus is situated on a long round porophore with two small papillae nearby; while in A. stricosus sp. nov., each male pore is on a coniform glandular disc surrounded by a round pad without papillae nearby. Furthermore, there are several genital papillae and accessory glands in the spermathecal pore region internally or externally in A. saccatus . However, none of them occur in A. stricosus sp. nov. Finally, the diverticulum of A. saccatus is shorter than the main spermathecal axis and is twisted heavily on its middle part, but the diverticulum is equal to the main spermathecal axis and more slender in A. stricosus sp. nov.