Amynthas orbicularis Sun and Jiang 2016, sp. nov.
Creators: name: Sun, Jing
name: Jiang, Jibao
name: Hu, Feng
name: Qiu, Jiangping
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Clitellata
Opisthopora
Megascolecidae
Amynthas
Amynthas orbicularis

description: Amynthas orbicularis Sun and Jiang sp. nov.
(Figure 2 (e–i))
Type material
Holotype: One clitellate (C-SC201102-19A) specimen: China, Sichuan Province, Mt. Emei (29°35 ′ 29 ″ N, 103°17 ′ 12 ″ E), 1300 m elevation, woods and bamboo, in black cinnamon soil, 27 July 2011, J. Sun, J.B. Jiang, X.D. Lei and H.W. Feng coll. Paratypes: A total of 10 specimens, as follows: Nine clitellate (C-SC201102-19B): Same data as for holotype. One clitellate (C-SC201102-21): Same data as for holotype.
Etymology
This is a descriptive name deriving from the dome-like male pore porophore.
Diagnosis
Two pairs of spermathecal pores in 7/8–8/9, slightly dorso-lateral; male pore porophore dome-like, glandular between two male pores; intestinal caeca complex with three slim and long finger-shaped sacs on dorsal margin; spermathecal diverticulum shorter than main spermathecal axis by 0.5, distal 0.5 twisted into zigzag seminal chamber, silver; three long stalked accessory glands medial to each prostatic duct root.
Description
External characters. Preserved specimens red and brown on dorsum, lacking pigment on ventrum. Mid-dorsal line pigmented. Dimensions 65–89 mm by 3.8–4.2 mm at
clitellum. Segment number 72–112. Body cylindrical in cross section, gradually tapered towards head and tail. Prostomium ½ epilobous. First dorsal pore in 12/13. Clitellum annular XIV–XVI, ring-shaped, no pigment, smooth, swollen; setae cannot be seen externally in clitellum, dorsal pores absent on clitellum. Setae uniformly distributed, dorsal breaks more distinct than ventral, 20–28 at III, 38–42 at V, 36–46 at VIII, 36–38 at XX, 36–40 at XXV; 9–10 between male pores; 20–28/VIII between spermathecal pores, setal formula AA = 1.0–1.2AB, ZZ = 1.2–1.8ZY. Spermathecal pores two pairs, in 7/8–8/9, intersegmental, slightly dorso-lateral (Figure 2 (e)). No genital papillae in this region. Male pores paired in XVIII, a little more than 0.33 circumference ventrally apart, each on a pad with a dome-like porophore in the centre, surrounded by 6–7 concentric ridges which are angular outside, skin between two male pores glandular. No genital papillae in this region (Figure 2 (f)). Female pore single, mid-ventral in XIV, elliptical.
Internal characters. Septa 6/7 thickened, 5/6, 7/8 and 10/11–12/13 slightly thickened, 8/9–9/10 absent. Dorsal blood vessel single, continuous onto pharynx; esophageal hearts four pairs in X–XIII, developed. Gizzard barrel-like, in VIII–X; intestine beginning to swell in XV; intestinal caeca complex, with three slim and long finger-shaped sacs on dorsal margin, smooth on ventral margin, originating in XXVII and extending forward to ½ XXIII (Figure 2 (g)). Male sexual system is holandric. Testis sacs two pairs, ventral in X and XI, anterior pair separated ventro-medially, posterior pair silver, connected ventromedially. Seminal vesicles paired in XI and XII, developed. Prostate glands developed, coarsely lobate, composed of two main lobes upper and lower section, respectively, the left lobe in XVI–½ XXIII, the right lobe in XVI–XXII, the distal end of prostatic duct musclar and club-shaped (Figure 2 (h)). Three long stalked accessory glands medial to each prostatic duct attachment to body wall in XVIII, corresponding with the tumid area outside. Female organs: Ovaries in XIII. Spermathecae paired in VIII–IX, the spermathecae in IX more developed than in VIII, about 2.1 mm long in IX; ampulla irregular massshaped with a gradual slender distal duct as long as 0.33 ampulla; diverticulum shorter than main spermathecal axis by 0.5, distal 0.5 twisted into zigzag shaped seminal chamber, silver; no nephridia on spermathecal ducts, genital marking not visible (Figure 2 (i)).
Remarks
Amynthas orbicularis sp. nov. keys to the Amynthas aeruginosus group (Sims and Easton 1972). This group is diagnosed by two pairs of spermathecal pores intersegmental in 7/8–8/9 and a holandric male sexual system. Amynthas omeimontis (Chen 1931), collected initially in Mt. Emei, Sichuan Province, China, and then reported in Mt. Fanjing, Guizhou Province (Qiu 1987), China, is similar with the new species in the following main characteristics: (1) some stalked accessory glands present near the distal end of prostate gland ducts; (2) two pairs of spermathecal pores in 7/8–8/9; (3) complex intestinal caeca with several finger-shaped sacs; (4) the spermathecal ampulla duct not longer than half the length of ampulla, and the diverticulum seminal chamber twisted into zigzag type. However, these two species have some differences. First, abundant papillae are present in XVIII and XI in A. omeimontis, but there are no papillae in the new species except a glandular region between two male pores. Second, the distance between the two spermathecal pores is about 0.42 body circumference in A. omeimontis, while it is slightly more than 0.5 of circumference ventrally apart in the new species. Third, the male apertures of A. omeimontis are in a shallow depression, but the male pores of the new species are on pads with a dome-like porophore in the centre and surrounded by 6–7 concentric ridges. Finally, both pairs of testis sacs are connected medially with their fellow in A. omeimontis, but the anterior pair of testis sacs is separated ventro-medially, and the posterior pair connected ventro-medially, in the new species. Accordingly, these two species can be distinguished clearly.
Four recently reported species in the A. aeruginosus group are Amynthas banlaoensis Hong, 2010, Amynthas khamlai Hong, 2010, Amynthas phadeangensis Hong, 2010 and Amynthas naphopensis Hong, 2010, all from Laos (Hong 2010). The morphological characters of these species were thoroughly compared with the new species; however, they are very different considering the long distance between the two spermathecal pores, lacking papillae on the male pores region and zigzag-shaped diverticulum seminal chamber for the new species. In contrast, four species from Laos have the distance between the two spermathecal pores shorter than half the circumference, some genital markings present on the male pore region, and the shape of the diverticulum seminal chamber not as complex as that of new species.
The partial COI sequence of the holotype of A. orbicularis sp. nov. has been deposited in the NCBI GenBank with accession number KF205481 (specimen C-SC 201102 -19A).
description: Published as part of Sun, Jing, Jiang, Jibao, Hu, Feng & Qiu, Jiangping, 2016, Four new earthworms of the genus Amynthas (Oligochaeta: Megascolecidae) from Mount Emei, Sichuan Province, China, pp. 2499-2513 in Journal of Natural History 50 on pages 2509-2511, DOI: 10.1080/00222933.2016.1193649, http://zenodo.org/record/3994511