Amynthas tortuosus Qiu & Dong

Dong, Yan, Law, Michelle Man Suet, Jiang, Jibao B. & Qiu, Jiangping P., 2019, Three new species and one subspecies of the Amynthas corticis - group from Guangxi Zhuang Autonomous Region, China (Oligochaeta, Megascolecidae), ZooKeys 884, pp. 23-42 : 23

Amynthas tortuosus Qiu & Dong sp. nov. Figure 3 , Table 3

Material.

Holotype: 1 clitellate (C-GX201306-06A): China, Guangxi Zhuang Autonomous Region, Shiwan Mountain Nature Reserve (21.84739°N, 107.88989°E), 553 m asl, black soil besides road, 13 May 2013, JP Qiu, Y Hong, JB Jiang, LL Zhang, Y Dong legit. Paratypes: 7 clitellates: 2 clitellates (C-GX201306-06B): same data as for holotype. 1 clitellate (C-GX201301-09): China, Guangxi Zhuang Autonomous Region, Shiwan Mountain Nature Reserve (21.48588°N, 107.57018°E), 130 m asl, black sandy soil at riverside, 11 May 2013, JP Qiu, Y Hong, JB Jiang, LL Zhang, Y Dong legit. 4 clitellates (C-GX201305-07): China, Guangxi Zhuang Autonomous Region, Shiwan Mountain Nature Reserve (21.50396°N, 107.53350°E), 494 m asl, black sandy soil besides road, 13 May 2013, JP Qiu, Y Hong, JB Jiang, LL Zhang, Y Dong legit.

Diagnosis.

Dimensions 55-86 mm by 2.5-2.8 mm at clitellum, 55-83 segments. First dorsal pore in 13/14. Setae numbering 24-26 at III, 34-36 at V, 34-36 at VIII, 32-36 at XX, 36-40 at XXV; 8-9 between male pores; setae between spermathecal pores numbering 9-12 at VI, 10-12 at VII, 12-13 at VIII. Four pairs of spermathecal pores in 5/6-8/9, eye-like. Four pairs of postsetal genital papillae in VI–IX, 0.20 circumference ventrally apart from each other. One pair of male pores in XVIII, each on the top of a central, round porophore surrounded by three or four rhombic ridges, with one presetal crescent indented-topped genital papilla medial of each male pore. Ampulla slender, heart-shaped; duct short. Diverticulum shorter than main pouch, terminal 4/5 slightly dilated into a swollen, S-shaped twisted seminal chamber. Prostate glands well developed.

Description.

External characters: Pre-clitellum, purple-brown pigment on dorsum, light purple-brown on ventrum. Post-clitellum, light purple-brown on dorsum, no pigment on ventrum. Clitellum taupe. Dimensions 76 mm by 27 mm at clitellum. 75 segments. Prostomium ½ epilobous. First dorsal pore in 13/14. Setae numbering 24 at III, 34 at V, 36 at VIII, 36 at XX, 40 at XXV; 8 between male pores; Setae between spermathecal pores numbering 11 at VI, 10 at VII, 13 at VIII. Setae formula AA = 1.2-2.0AB, ZZ = 1.4-2.0ZY. Clitellum annular, pale taupe, in XIV–XVI, setae not visible externally. Four pairs of spermathecal pores in 5/6-8/9, eye-like, 0.25 circumference ventrally apart from each other. Four pairs of postsetal genital papillae in VI–IX, 0.20 circumference ventrally apart from each other. One pair of male pores in XVIII, 0.25 circumference apart ventrally, each on the top of a central, round porophore surrounded by three or four rhombic ridges, with one presetal crescent indented-topped genital papilla in the center of each male pore region ( Figure 2A ). Single female pore in XIV.

Internal characters. Septa 5/6-7/8 thick and muscular, 10/11-12/13 slightly thickened, 8/9-9/10 absent. Gizzard ball-shaped, in VIII–X. Intestine enlarged distinctly from XVI onwards. Intestinal caeca paired in XXVII, simple, smooth, extending anteriorly to XXIV. Four pairs of esophageal hearts in X–XIII, the first pair very thin, the last three pairs developed. Ovaries in XIII. Four pairs of spermathecae in VI–IX, small, 2.4 mm long. Ampulla slender, heart-shaped; duct short. Diverticulum 2.0 mm long, slightly shorter than main pouch, terminal 4/5 slightly dilated into a swollen, S-shaped twisted seminal chamber ( Figure 2B ). One stalked accessory gland observed medial to each spermathecal duct. Holandric: two pairs of testis sacs in X–XI, separated from each other, developed. Two pairs of seminal vesicles in XI–XII, well developed. Prostate glands well developed, inserting in XVIII and extending from XVII–XXII, coarsely lobate, prostatic duct C-shaped, uniform thickness. No accessory glands observed.

Etymology.

The species is named after the crooked shape of its diverticulum.

Remarks.

Amynthas tortuosus sp. nov. is a comparatively small earthworm and shares some similarities to A. carnosus and A. corticis . All of them have genital markings both on the spermathecal and the male pore regions and share similar setal numbers. However, the body size of A. tortuosus sp. nov. is very distinct from others. The new species has roughly half the body size of A. carnosus and A. corticis , both in length and width. The first dorsal pore is in 13/14 and the distance between the spermathecal pores and male pores is less than those of A. carnosus and A. corticis . Moreover, A. tortuosus sp. nov. has long diverticulum with an S-shaped twisted seminal chamber and eight stalked accessory glands observed near the spermathecal duct, rather than a straight or slender stalk and an absence of accessory glands in A. carnosus .

We also compare the new species with Amynthas homosetus ( Chen 1938) described from Hainan Island, which has a very similar distance between the male pores and spermathecal pores, and similar setal numbers. The differences between the two species are as follows: the body size of A. tortuosus is much smaller than A. homosetus ; the size of prostate glands is larger in A. tortuosus ; the shape of the seminal chamber is S-shaped twisted in A. tortuosus , while it is ovoid in A. homosetus ; and several genital markings are present in the spermathecal pore region and male pore region in A. tortuosus sp. nov., while these markings are absent in A. homosetus .

The body size of A. tortuosus sp. nov. is similar to Amynthas exiguus aquilonius Tsai et al., 2001 described from Taiwan Island and Amynthas stricosus Qiu & Sun, 2012 described from Hainan Island. The first dorsal pore of the new species is in 13/14, but in 6/7 in A. exiguus aquilonius , and in 11/12 or 12/13 in A. stricosus . The new species has more closely spaced spermathecal pores than A. exiguus aquilonius and A. stricosus . Additionally, A. exiguus aquilonius has more genital papillae observed in spermathecal pores and male pores region than the new species. Accessory glands are observed in spermathecal pores and male pores region in A. exiguus aquilonius , but in the new species, accessory glands are only observed in spermathecal pores region. Furthermore, A. stricosus has a band shaped chamber, no genital papillae near spermathecal pores region, no accessory glands, and papillae observed in XVII, XIX and XX, but the new species has a S-shaped twisted seminal chamber, four pairs of genital papillae in spermathecal pores region, accessory glands near spermathecal duct, and no genital papillae observed in XVII, XIX and XX. Details of the comparison are showed in table 3.

Figures

Figure 2. A Ventral view showing spermathecal pores, female pores and male pores of Amynthas maximus sp. nov. B spermathecae of Amynthas maximus sp. nov. C illustration of the details of the male pore region.

Figure 3. A Ventral view showing spermathecal pores, female pores and male pores of Amynthas tortuosus sp. nov. B spermathecae of Amynthas tortuosus sp. nov. C illustration of the details of the male pore region.