Amynthas dongyinensis Shen, 2013

Shen, Huei-Ping, Chang, Chih-Han & Chih, Wen-Jay, 2013, Five new earthworm species of the genera Amynthas and Metaphire (Megascolecidae: Oligochaeta) from Matsu, Taiwan, Journal of Natural History (J. Nat. Hist.) 48 (9 - 10), pp. 495-522 : 506-510

Amynthas dongyinensis Shen , sp. nov.

( Figure 5 )

Type material

Holotype. Clitellate (mature) specimen (62 mm in length, dissected) collected 28 June 2012 beside the Yanhsiu Fort (elevation 19 m), Dongyin by H.P. Chen and W.J. Chih (TESRI-O-H-40) (voucher number: MTS 120). Paratypes. Four clitellates [one dissected (voucher number: MTS 114)] collected 28 June 2012 from roadside ditches outside Stronghold No. 33 (elevation 40 m), Hsiyin by H.P. Chen and W.J. Chih (TESRI-O-P-35).

Other material

Three clitellates (voucher number of specimen used for DNA barcoding analyses: MTS 113) and two aclitellates collected 28 June 2012 under a tree at Stronghold No. 33 (elevation 61 m), Hsiyin by H.P. Chen and W.J. Chih (coll. no. 2012–72); three clitellates (voucher number of specimen used for DNA barcoding analyses: MTS 117) and two aclitellates collected 28 June 2012 near Northernmost Frontier (elevation 79 m), Hsiyin by H.P. Chen and W.J. Chih (coll. no. 2012–75); two clitellates collected 28 June 2012 from a roadside ditch near Stronghold No. 26 (elevation 19 m), Hsiyin by H.P. Chen and W.J. Chih (coll. no. 2012–76) (voucher number of specimen used for DNA barcoding analyses: MTS 119); one clitellate collected 28 June 2012 beside the Yanhsiu Fort (elevation 19 m), Dongyin by H.P. Chen and W.J. Chih (coll. no. 2012–78); one clitellate collected 30 August 2012 from a ditch under Drum Rock (elevation 99 m) on the way to Dongyong Lighthouse, Dongyin by H.P. Chen and H.H. Huang (coll. no. 2012–121) (voucher number: MTS 122); one clitellate collected 31 August 2012 from Chingshuiao (elevation 15 m), Hsiyin by H.P. Chen and H.H. Huang (coll. no. 2012–124) (voucher number: MTS 125); three aclitellates collected 31 August 2012 around Dongyong Reservoir (elevation 40 m), Dongyin by H.P. Chen and H.H. Huang (coll. no. 2012–126); one clitellate collected 31 August 2012 from a ditch beside the coastline between Huangpaitan and Mopantou (elevation 68 m), Dongyin by H.P. Chen and H.H. Huang (coll. no. 2012– 129) (voucher number: MTS 128); nine aclitellates collected 31 August 2012 near Zhongling Temple (elevation 76 m), Dongyin by H.P. Chen and H.H. Huang (coll. no. 2012–130).

Diagnosis

Small to medium; length (clitellates) 49–91 mm. Segments numbering 91–113. Setae 38–54 in VII, 38–57 in XX, 7–9 between male pores. First dorsal pore in 12/13. Spermathecal pores three pairs in 6/7–8/9, 0.28–0.31 body circumference ventrally apart, each pore on a tubercle or papilla about 0.3 mm in diameter. Male pores 0.26– 0.3 body circumference ventrally apart in XVIII, each on a round porophore surrounded by one or two circular or diamond-shaped folds. Genital papillae absent. Spermathecae three pairs in VII–IX. Accessory glands sessile, each corresponding to external spermathecal papilla. Seminal vesicles large, two pairs in XI and XII, each vesicle with a round, prominent dorsal lobe. Prostate glands large, occupying five to six segments in XVI–XXI. Prostatic duct small, C- or U-shaped in XVIII. Accessory glands absent in the postclitellar region.

Description

External characters. Total length (clitellates) 49–91 mm. Weight 0.37–1.08 g. Segments numbering 91–113. Clitellum XIV–XVI, setae and dorsal pores absent, length 1.43–4.98 mm and width 2.84–4.06 mm. Prostomium epilobous. Setal number 38–54 in VII, 38–57 in XX, and 7–9 between male pores in XVIII. First dorsal pore in 12/13. Spermathecal pores three pairs in intersegmental furrows of 6/7–8/9, distance between paired pores 0.28–0.31 body circumference ventrally apart, each pore on a tubercle or papilla about 0.3 mm in diameter ( Figure 5A ). No other genital papilla in the preclitellar region. Female pore single, mid-ventral in XIV.

Male pores paired in XVIII, 0.26–0.3 body circumference ventrally apart. Each pore on a round porophore surrounded by one or two circular or diamond-shaped folds ( Figure 5B ). Genital papillae absent in the postclitellar region.

Preserved specimens brown in colour with dark brown clitellum.

Internal characters. Septa 5/6–7/8 thick, 10/11–13/14 thickened, 8/9/10 absent. Nephridial tufts on anterior faces of 5/6/7. Gizzard large in VIII–X. Intestine enlarged from XV. Intestinal caeca paired in XXVII, extending anteriorly to XXII–XXIII, each simple, slender, straight. Oesophageal hearts in XI–XIII.

Spermathecae three pairs in VII–IX, varied in size and shape ( Figure 5C ). Each ampulla round, peach-shaped or elongated oval-shaped, surface wrinkled, 0.81–1.81 mm long and 0.65–1.57 mm wide, with a stout spermathecal stalk of 0.2–0.6 mm in length. Diverticulum with an iridescent, oval- or rod-shaped seminal chamber of 0.4–0.85 mm long and a long, slender to stout stalk of 0.84–2.1 mm in length. Accessory glands sessile, round or slightly lobed, 0.3 mm in diameter, each corresponding to external spermathecal papilla ( Figure 5C ).

Holandry: testes large, oval, two pairs in ventrally joined sacs in X and XI. Seminal vesicles large, smooth, two pairs in XI and XII, anterior pair occupying the full segmental compartment, posterior pair smaller, about one-half to two-thirds of segment, each vesicle with a round, prominent dorsal lobe. Prostate glands large, lobed with follicular surface, occupying five to six segments in XVI–XXI ( Figure 5D ). Prostatic duct small, C-shaped or U-shaped in XVIII. Accessory glands absent.

DNA barcodes

GenBank accession numbers KC897044 (MTS 120, holotype), KC897049 (MTS 114, dissected paratype), KC897047 , KC897046 , KC897043 , KC897042 , KC897045 and KC897048 (MTS 113, 117, 119, 122, 125 and 128, respectively) .

Etymology

The name dongyinensis is given to this species with reference to its holotype locality in Dongyin , Matsu .

Remarks

Amynthas dongyinensis sp. nov. is only found on the islands of Dongyin and Hsiyin. It is a sexthecate earthworm with three pairs of spermathecal pores in intersegmental furrows of 6/7–8/9, belonging to the sieboldi species-group of the genus Amynthas ( Sims and Easton 1972) . It has simple male pore structure and no genital papillae (except spermathecal papillae). Among the species of the sieboldi -group listed by Sims and Easton (1972), Amynthas udei ( Rosa, 1896) from Sumatra, and Amynthas buitendijki ( Michaelsen, 1922) and Amynthas dammermani ( Michaelsen, 1924) from Java also have simple male pore structure without any preclitellar or postclitellar papilla. Both the latter two species described by Michaelsen have heavily coiled diverticulum, which is distinctly different from the simple diverticulum structure of A. dongyinensis ( Michaelsen, 1922, 1924). Amynthas dongyinensis is morphologically fairly similar to A. udei ( Table 2). However, A. dongyinensis has longer diverticular stalk and large prostate glands occupying five to six segments in XVI–XXI and A. udei has short diverticular stalk and small, transversely oval prostate glands in XVIII ( Rosa 1896).

The simple male pore structure and absence of genital papillae of A. dongyinensis are also similar to that of Amynthas kamitai ( Kobayashi, 1934) and Amynthas minjae Hong, 2001 from Korea. However, both species from Korea are sexthecate with three pairs of spermathecal pores in 5/6–7/8, and have small seminal vesicles and smaller prostate glands (XVII–XIX in A. kamitai and XVII–XX in A. minjae ) ( Kobayashi 1934; Hong et al. 2001). Amynthas kamitai and A. minjae are fairly similar and not easily distinguishable ( Table 2). The former has small seminal chamber and prostate glands divided into three main lobes in XVII–XIX, while the latter has stick-shaped diverticulum without terminal expansion and prostate glands divided into two main lobes in XVII–XX ( Kobayashi 1934; Hong et al. 2001). Since only two specimens of A. kamitai were collected ( Kobayashi 1934), it is possible that such differences might be due to individual variation.

Zhao et al. (2013) recently described Amynthas apapillatus based on a single specimen collected from Hainan Island, China. It is fairly similar to A. dongyinensis in that both species belong to the sieboldi species-group, and have simple male pore structure and no genital papillae. However, A. dongyinensis has oesophageal hearts in XI–XIII and large prostate glands occupying five to six segments in XVI–XXI, while A. apapillatus has oesophageal hearts in X–XIII and small prostate glands in XVII– XVIII. Molecular analyses also show that A. dongyinensis is distinctly different from A. apapillatus ( Figure 2 ).

Figures

Figure 2. Neighbour-joining tree of the five new species and several other Amynthas based on cytochrome oxidase c subunit I (COI) gene and rooted using Metaphire californica. Specimens from this study and sequences retrieved from GenBank are shown by their voucher numbers and GenBank accession numbers, respectively. Numbers around nodes are bootstrap values above 50.

Figure 5. Amynthas dongyinensis sp. nov. Holotype (TESRI-O-H-40) (voucher number: MTS 120). (A) Right lateral view of spermathecal pore region (sp, spermathecal papilla); (B) ventral view of male pore region (mp, male porophore); (C) dorsal view of right spermathecae (amp, ampulla; dv, diverticulum; ag, accessory gland); (D) dorsal view of left prostate gland (pd, prostatic duct). Scale bar 1 mm.