Amynthas gilvus Sun and Qiu, 2016

Sun, Jing, Jiang, Jibao, Hu, Feng & Qiu, Jiangping, 2016, Four new earthworms of the genus Amynthas (Oligochaeta: Megascolecidae) from Mount Emei, Sichuan Province, China, Journal of Natural History 50, pp. 2499-2513 : 2503-2505

Amynthas gilvus Sun and Qiu sp. nov.

( Figure 1 (e–g))

Type material

Holotype: One clitellate (C-SC201102-12A) 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. Paratype: One clitellate (C-SC201102-12B): Same data as for holotype.

Etymology

The species name gilvus , which means light yellow, refers to the pigment of the clitellum.

Diagnosis

Three pairs of spermathecal pores in 6/7–8/9; first dorsal pore in 13/14, but also present in 4/5–6/7; each male pore on a slightly raised elliptical glandular flat-top pad, with a pointed extension lateral to each porophore; the first pair of seminal vesicles is enclosed in the second pair of testis sacs; spermathecal diverticulum shorter than main spermathecal axis by 0.61, distal 0.75 dilated into longer chili pepper-shaped seminal chamber.

Description

External characters. Preserved specimens light cinnamon on dorsum, and lacking pigment on ventrum. Mid-dorsal line pigmented. Dimensions 41–59 mm by 2.3– 2.8 mm at clitellum, segments number 77–108. Body cylindrical in cross section, and gradually tapered towards head and tail. Secondary annulations absent. Prostomium ½ epilobous. First dorsal pore in 13/14, but also present in 4/5–6/7. Clitellum annular in XIV–XVI, lacking pigment, smooth, swollen, setae not visible on clitellum, the trace of dorsal pores very clear on clitellum, but not forming a hole. Setae uniformly distributed, dorsal breaks more distinct than ventral, 22–24 at III, 24–40 at V, 32–36 at VIII, 22–40 at XX, 30–42 at XXV; 6–7 between male pores; 12–16/VII, 11–15/VIII between spermathecal pores, setal formula AA = 1–1.2AB, ZZ = 1.2–1.8ZY. Spermathecal pores three pairs, in 6/ 7–8/9, inconspicuous, intersegmental, about 0.33 of circumference ventrally apart, inconspicuous. No genital papillae in this region. Male pores paired in XVIII, 0.33 of circumference ventrally apart; each on a slightly raised elliptical glandular flat-top pad, with a lateral pointed extension of each porophore, without circular ridges surrounding ( Figure 1 (e)). Genital markings not visible externally. Female pore single, mid-ventral in XIV, elliptical, situated in a depression.

Internal characters. Septa 5/6–7/8 and 10/11–13/14 slightly thickened, 8/9–9/10 absent. Dorsal blood vessel single, continuous onto pharynx; esophageal hearts four pairs in X–XIII. Gizzard barrel-like, in VIII–X; intestine beginning to swell in XV; intestinal caeca simple, originating in XXVII and extending forward to XXIII, hornshaped sac, surface smooth ( Figure 1 (f)). Male sexual system is holandric. Testis sacs two pairs, ventral in X and XI, silver, separated ventro-medially. Seminal vesicles paired in XI and XII, separated ventro-medially, anterior pair are enclosed in posterior pair of testis sacs, dorsal lobe of anterior pair is highly developed, extending to X. Prostate glands developed, coarsely lobate, thick, in XVI–XXII, ducts U-curved, distal end stout. No accessory glands observed. Female organs: Ovaries in XIII. Spermathecae paired in VII–IX, about 1.8 mm long; ampulla oval-shaped, with a short duct, about 0.3 mm; diverticulum shorter than main spermathecal axis by 0.61, distal 0.75 dilated into longer chili pepper-shaped seminal chamber; no nephridia on spermathecal ducts ( Figure 1 (g)).

Remarks

Amynthas gilvus sp. nov. also keys to the Amynthas sieboldi group ( Sims and Easton 1972). This new species is close to two species – Amynthas jaoi ( Chen 1946) and Amynthas loti (Chen and Hsü) .

Amynthas gilvus sp. nov. resembles A. jaoi in such characters as: (1) the body size is relatively small; (2) the spermathecal pores are three pairs in 6/7–8/9 with the distance about 0.33 of circumference ventrally apart; (3) the simple intestinal caeca; (4) the spermathecal duct is short; (5) the prostates are developed. However, they differ as follows: (1) the pigment of the new species is not as dark as that of A. jaoi ; (2) the number of setae per segment for the new species is lower than in A. jaoi ; (3) the first dorsal pore of the new species is 13/14 but the pores in 4/5–6/7 are present, in contrast with the first dorsal pore in 12/13 for A. jaoi ; (4) the male pore porophores have the lateral points but are without other genital markings in the male pore region for the new species; in contrast the male porophore is a single round papilla and with an accompanying postsetal genital marking for A. jaoi ; (5) the diverticulum of the new species is clearly shorter than the main spermathecal axis; however it is longer than the main pouch for A. jaoi ; (6) the first pair of seminal vesicles is enclosed in the second pair of testis sacs for the new species, while this is not the case for A. jaoi ; (7) the prostatic duct is unusual and shows a double U-curve shape for A. jaoi , while it is a more typical, simple U-curve shape for the new species; (8) there are no observed accessory glands for the new species, but inconspicuous and sessile accessory glands are present in A. jaoi .

Considering the decolouring effect of anhydrous ethanol, A. gilvus sp. nov. and A. loti have the similar pigment, even though the pigment is described as light cinnamon on the dorsum for the new species but red-brown on the dorsum for A. loti ; the density of setae is similar for the two species; the spermathecal pores are located in 6/7–8/9 for both species; and they both have a simple intestinal caeca. Nevertheless, these two species can be distinguished on the following main aspects: (1) the distance between the two spermathecal pores of A. loti is bigger than in the new species, and two pairs of genital papillae are present on VII and VIII for A. loti but absent for the new species; (2) the male pore porophore is cone-like and surrounded by 3–4 circles in A. loti , but it is a slightly raised elliptical glandular flat-top pad accompanied by a tail in the new one; (3) the septa in 8/9– 9/10 is membranous in A. loti , but absent in the new species; (4) the seminal chamber of A. loti is ovoid-like but long pepper-shaped in the new species; (5) there is not a developed prostate gland in A. loti , but it is developed in the new species; (6) the ball-like accessory gland is present on the spermathecal region in A. loti , but there is no accessory gland in the new species; (7) the first pair of seminal vesicles are enclosed in the second pair of testis sacs of the new species, but this is not the case for A. loti .

The partial COI sequence of the holotype of A. gilvus sp. nov. has been deposited in the NCBI GenBank with accession number KF205478 (specimen C-SC 201102 -12A) .

Figures

Figure 1. (a) Amynthas leshanensis Sun and Qiu sp. nov., holotype, spermathecal pores; (b) A. leshanensis sp. nov., male pore region; (c) A. leshanensis sp. nov., intestinal caecum; (d) A. leshanensis sp. nov., spermathecae. (e) Amynthas gilvus Sun and Qiu sp. nov., holotype, male pore region; (f) A. gilvus sp. nov., intestinal caecum; (g) A. gilvus sp. nov., spermathecae.