Amynthas dongjuensis Shen and Chang, 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 : 510-514

Amynthas dongjuensis Shen and Chang , sp. nov.

( Figure 6 )

Type material

Holotype. Clitellate (mature) specimen (132 mm in length, dissected) collected 30 May 2012 from roadside slopes and ditches around Dongju Lighthouse (elevation 63 m), Dongju by H.P. Chen and T. L. Ai (TESRI-O-H-41) (voucher number: MTS 58).

Paratypes. Three clitellates [one dissected (voucher number: MTS 46)] and four aclitellates collected 30 May 2012 from roadside slopes (elevation 29 m), Kunchiu, Hsiju by H.P. Chen and T. L. Ai (TESRI-O-P-36) .

Other material

One clitellate (voucher number: MTS 41) and two aclitellates collected 30 May 2012 from roadside ditches around Hsiju Visitor Centre (elevation 29 m), Hsiju by H.P. Chen and T.L. Ai (coll. no. 2012–44); two clitellates collected 30 May 2012 from roadside litter at crossroads from Central Road toward Hsichiu Village (elevation 106 m), Hsiju by H.P. Chen and T.L. Ai (coll. no. 2012–47); an aclitellate collected 30 May 2012 from roadside slopes and ditches around Dongju Lighthouse (elevation 63 m), Dongju by H.P. Chen and T.L. Ai (coll. no. 2012–49); two clitellates (voucher number of specimen used for DNA barcoding analyses: MTS 63) and two aclitellates collected 30 May 2012 around Dapu Village (elevation 46 m), Dongju by H.P. Chen and T.L. Ai (coll. no. 2012–50); an aclitellate collected 30 May 2012 near Dapu Stone Inscription (elevation 46 m), Dongju by H.P. Chen and T.L. Ai (coll. no. 2012–51); 16 clitellates collected 27 June 2012 at Fuzheng Reservoir (elevation 23 m), Dongju by H.P. Chen and W.J. Chih (coll. no. 2012–66); four clitellates collected 27 June 2012 at Chipinglong (elevation 50 m), Dongju by H.P. Chen and W.J. Chih (coll. no. 2012–67); four clitellates and an aclitellate collected 27 June 2012 above the tidal zone (elevation 8 m) near Dapu Stone Inscription, Dongju by H.P. Chen and W.J. Chih (coll. no. 2012–68); two clitellates collected 27 June 2012 in front of Tsaipuao Reservoir (elevation 17 m), Hsiju by H.P. Chen and W.J. Chih (coll. no. 2012–69); one clitellate (dissected) collected 27 June 2012 from roadside litter at crossroads from Central Road toward Hsichiu Village (elevation 106 m), Hsiju by H.P. Chen and W. J. Chih (coll. no. 2012–70); two clitellates [one dissected (voucher number: MTS 115)] collected 28 June 2012 from Chingshuiao (elevation 15 m), Hsiyin by H.P. Chen and W.J. Chih (coll. no. 2012–74); 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 118); two clitellates collected 28 June 2012 beside the Yanhsiu Fort (elevation 19 m), Dongyin by H.P. Chen and W.J. Chih (coll. no. 2012–78); four clitellates and an aclitellate collected 29 August 2012 near Dapu Stone Inscription (elevation 46 m), Dongju by H.P. Chen and H.H. Huang (coll. no. 2012–118); one clitellate collected 29 August 2012 near Mysterious Little Bay (elevation 6 m), Dongju by H.P. Chen and H.H. Huang (coll. no. 2012–119); four clitellates and two aclitellates collected 30 August 2012 at A Thread of Sky (elevation 60 m), Dongyin by H.P. Chen and H.H. Huang (coll. no. 2012–120); one clitellate (voucher number: MTS 121) and two aclitellates 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); three clitellates collected 31 August 2012 from Chingshuiao (elevation 15 m), Hsiyin by H.P. Chen and H.H. Huang (coll. no. 2012–124) (voucher number of specimen used for DNA barcoding analyses: MTS 123); four clitellates 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 roadside ditch outside Beiao (elevation 51 m), Dongyin by H.P. Chen and H.H. Huang (coll. no. 2012–127); one clitellate collected 31 August 2012 around Hsiaozihao Reservoir (elevation 51 m), Dongyin by H.P. Chen and H.H. Huang (coll. no. 2012–128) (voucher number: MTS 127).

Diagnosis

Small to medium; length (clitellates) 88–177 mm. Segments numbering 85–122. Setae 31– 48 in VII, 36–56 in XX, 0–6 on ventral XVI, and 5–11 between male pores. First dorsal pore in 12/13 or 13/14. Spermathecal pores four pairs in 5/6–8/9, 0.23–0.31 body circumference ventrally apart. Male pores 0.28–0.33 body circumference ventrally apart in XVIII, each inconspicuous on the depressed centre of a round porophore 0.5–0.7 mm in diameter, or each on a papilla-like porophore with a genital papilla on the setal line medial to it. Spermathecae four pairs in VI–IX. Seminal vesicles large, two pairs in XI and XII. Prostate glands compact in XVII–XIX, or large, rectangular-shaped, occupying five to six segments in XV–XXI. Prostatic duct short, C- or S-shaped in XVIII. Accessory glands absent or large, sessile, corresponding to external genital papillae.

Description

External characters. Total length (clitellates) 88–177 mm. Weight 0.74–3.19 g. Segments numbering 85–122. Clitellum XIV–XVI, dorsal pores absent, 0–6 setae on ventral XVI, length 2.6–6.13 mm and width 3.31–5.45 mm. Prostomium epilobous. Setal number 31– 48 in VII, 36–56 in XX, and 5–11 between male pores in XVIII. First dorsal pore in 12/13 or 13/14. Spermathecal pores four pairs in intersegmental furrows of 5/6–8/9, distance between paired pores 0.23–0.31 body circumference ventrally apart. Genital papillae absent in the preclitellar region. Female pore single, mid-ventral in XIV.

Male pores paired in XVIII, 0.28–0.33 body circumference ventrally apart. Each pore inconspicuous on the depressed centre of a round porophore 0.5–0.7 mm in diameter, surrounded by one to three circular or diamond-shaped folds, the whole male area slightly elevated ( Figure 6A ), or each pore on a papilla-like porophore 0.55–0.7 mm in diameter, with a genital papilla on the setal line medial to it, surrounded by one or two skin folds ( Figure 6D ). Genital papillae round, 0.75–0.8 mm in diameter with concave centre. Other genital papillae absent in the postclitellar region.

Preserved specimens dark brown on dorsum and clitellum, and greyish brown on ventrum.

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

Spermathecae four pairs in VI–IX, varied in sizes and shapes ( Figure 6B, E ). Each ampulla peach-shaped or elongated oval-shaped, surface wrinkled, 0.82–3.25 mm long and 0.6–2.03 mm wide, with a stout spermathecal stalk of 0.25–1.27 mm in length. Diverticulum with a slender stalk of 0.55–2.2 mm in length and a rod- or ovalshaped seminal chamber of 0.36–1.25 mm long. Accessory glands absent.

Holandry: testes large, oval, two pairs in ventrally joined sacs in X and XI. Seminal vesicles large, finely folliculated, two pairs in XI and XII, occupying the full segmental compartment, each vesicle with a round or elongated oval dorsal lobe. Pseudovesicles absent or vestigial, paired in XIII. Prostate glands compact in XVII–XIX ( Figure 6C ), or large, rectangular-shaped, lobed with wrinkled surface, occupying five to six segments in XV–XXI ( Figure 6F ). Prostatic duct short, slender to stout, C-shaped or S-shaped in XVIII. Accessory glands absent, or large, sessile, slightly lobed, 0.4–0.75 mm wide, 1.25– 1.31 mm long, corresponding to external genital papillae ( Figure 6F ).

DNA barcodes

GenBank accession numbers KC897053 (MTS 58, holotype), KC897061 (MTS 46, dissected paratype), KC897057 , KC897056 , KC897059 , KC897055 , KC897058 , KC897060 and KC897054 (MTS 41, 63, 115, 118, 121, 123 and 127, respectively) .

Etymology

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

Remarks

Amynthas dongjuensis sp. nov. is common on the islands of Dongju, Hsiju, Dongyin and Hsiyin. Individuals from Hsiju have one genital papilla medial to each male pore and have large prostate glands occupying five to six segments in XV–XXI and large, sessile accessory glands corresponding to the genital papillae, whereas individuals from the other islands have simple male pore structure without genital papilla or genital marking and have compact prostate glands in XVII–XIX. However, the genetic evidence reflects the geographic distance. Molecular analyses show that A. dongjuensis is composed of two groups consistent with their geographic distributions with those from Dongju and Hsiju more closely related to each other while those from Dongyin and Hsiyin forming another group ( Figure 2 ).

Amynthas dongjuensis is an octothecate earthworm and most of the individuals have simple male pore structure without genital papilla or genital marking. These characters are similar to that of Amynthas taiwumontis Shen et al., 2013 from Kinmen, Amynthas fornicatus ( Gates, 1935) from Sichuan, China, Amynthas penpuensis Shen et al., 2003 from Taiwan, Amynthas marenzelleri ( Cognetti, 1906) and Amynthas toriii ( Ohfuchi, 1941) from Japan, Amynthas baemsagolensis Hong and James, 2001 from Korea, Amynthas sinabunganus ( Michaelsen, 1923) from Sumatra, Amynthas tertiadamae ( Michaelsen, 1934) from Gulf of Siam, and Amynthas trinitatis ( Beddard, 1896) from Trinidad. Though these species look similar, there are distinct differences among them ( Table 3). Among the above species, A. taiwumontis has much higher setal number than the others with 74–97 setae in VII and 73–89 setae in XX ( Table 3). In addition, the more anterior position of the first dorsal pore in 5/6 or 6/7 of A. penpuensis distinguishes this species from the others ( Table 3). Molecular analyses also show that A. dongjuensis is distinct from A. corticis , A. penpuensis and A. taiwumontis ( Figure 2 ). To sum up, A. dongjuensis is most similar to A. marenzelleri by having similar setal number, large, round or oval male porophore, small prostate glands, and short, C- or S-shaped prostatic ducts ( Table 3). However, A. marenzelleri is much larger (length 160–190 mm and diameter 6– 7 mm with 130–138 segments), and has small spermathecae without diverticulum ( Kobayashi 1938b). Amynthas dongjuensis is also similar to A. fornicatus . The two species can be distinguishable by the characters of shape and structure of diverticulum and seminal vesicle. Amynthas dongjuensis has large seminal vesicles and has diverticulum with a rod-shaped or small, oval-shaped seminal chamber, whereas A. fornicatus has small and elongate seminal vesicles and has diverticulum with a distended seminal chamber ( Chen 1936). Also, A. fornicatus has lower segment number and higher setal number than A. dongjuensis ( Table 3).

Individuals of A. dongjuensis from Hsiju have one genital papilla medial to each male pore. Similar papillae arrangements can also be found in Amynthas jaoi ( Chen, 1946) from Sichuan, China and Amynthas taipeiensis ( Tsai, 1964) from northern Taiwan and Fujian, China (= Pheretima heterogens Chen and Hsü, 1975 ). Amynthas jaoi is a small earthworm with body length about 38 mm in length and 1.5–2 mm in width, and has long, U-shaped prostatic ducts ( Chen 1946). Amynthas taipeiensis has coiled diverticulum and long, coiled or U-shaped prostatic ducts ( Tsai 1964; Chen et al. 1975). Both A. jaoi and A. taipeiensis are sexthecate with three pairs of spermathecal pores in 6/7–8/9, so A. dongjuensis is easily distinguishable from these two species.

Also, the male pore structure with its genital papilla medial to the male porophore of A. dongjuensis is similar to that of Amynthas sheni ( Chen, 1935) from Hong Kong and Amynthas chilanensis Tsai and Tsai, 2007 from Taiwan. However, A. dongjuensis has fully developed reproductive organs, whereas A. sheni is athecate ( Chen 1935) and A. chilanensis is nearly athecate ( Tsai et al. 2007). Also, A. dongjuensis has large seminal vesicles and short, C-shaped prostatic ducts, differing significantly from the small seminal vesicles and long, U-curved prostatic ducts of A. sheni and A. chilanensis ( Chen 1935; Tsai et al. 2007).

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 6. Amynthas dongjuensis sp. nov. (A) Ventral view of male pore region of holotype (TESRI-O-H-41) (voucher number: MTS 58) (mp, male porophore); (B) dorsal view of right spermathecae of holotype (amp, ampulla; dv, diverticulum); (C) dorsal view of left prostate gland of holotype (pd, prostatic duct); (D) ventral view of male pore region of the dissected paratype (TESRI-O-P-36) (voucher number: MTS 46) (gp, genital papilla); (E) dorsal view of left spermathecae of the dissected paratype; (F) dorsal view of left prostate gland of the dissected paratype (ag, accessory gland). Scale bar 1 mm.