Amynthas nanganensis beiganensis Shen & Chang

Shen, Huei-Ping, Chang, Chih-Han & Chih, Wen-Jay, 2015, Earthworms from Matsu, Taiwan with descriptions of new species of the genera Amynthas (Oligochaeta: Megascolecidae) and Drawida (Oligochaeta: Moniligastridae), Zootaxa 3973 (3), pp. 425-450 : 429-433

Amynthas nanganensis beiganensis Shen & Chang , ssp. nov.

( Figure 2 )

Holotype: Clitellate (mature) specimen (117 mm in total length, dissected), Beigan, Tangchi Village, near a trash treatment field, 26°13'59.9''N, 120°00'17.4''E, 64 m asl, 26 June 2012, H.P. Chen & W.J. Chih (TESRI-O-H-44; MTS 92).

Paratypes: 2 clitellates, Beigan, in front of Banli Reservoir, 26°13'11.7''N, 119°58'27.1''E, 33 m asl, 29 May 2012, H.P. Chen & T.L. Ai (TESRI-O-P-39; MTS 19).

Other material. 9 specimens altogether. 2 clitellates, Beigan, from a roadside ditch at Chinbi Village, 26°13'32.0''N, 119°59'03.3''E, 11 m asl, 29 May 2012, H.P. Chen & T.L. Ai (TESRI-O- 2012-39 -7; MTS 137); 1 clitellate, Beigan, from a roadside ditch outside Tangchi Village, 26°13'44.2''N, 119°59'51.9''E, 44 m asl, 29 May 2012, H.P. Chen & T.L. Ai (TESRI-O- 2012-40 -1; MTS 31); 3 clitellates and 3 aclitellates, Beigan, around Bishan Lookout, 26°13'30.9''N, 119°59'33.3''E, 258 m asl, 26 June 2012, H.P. Chen & W.J. Chih (TESRI-O- 2012-62 -1; MTS 102).

Diagnosis. Medium to large; length (clitellates) 103–186 mm. Segments numbering 110–130. Setae 64–77 in VII, 73–89 in XX, and 19–26 between male pores. First dorsal pore in 12/13. Spermathecal pores dorso-lateral, two pairs in 7/8/9, 0.36–0.39 body circumference dorsally apart, with one right and one left papillae immediately adjacent to each pore. Preclitellar genital papillae small, 1–7 in a transverse row in each of presetal and postsetal IX. Male pores 0.29–0.35 body circumference ventrally apart in XVIII, each on a small, round porophore surrounded by 3–7 papillae, within a round or oval area. Postclitellar genital papillae 3–8 in a transverse row in each of presetal and postsetal XVIII. Spermathecae two pairs in VII and IX, or in VIII and IX. Diverticulum coiled. Seminal vesicles large, two pairs in XI and XII. Prostate glands large in XVI–XXII. Prostatic duct C- or U-shaped in XVIII. Accessory glands stalked, mushroom-like, corresponding to external genital papillae.

Description. External: Total length (clitellates) 103–186 mm. Weight 1.66–3.66 g. Segments numbering 110– 130. Clitellum XIV–XVI, setae 0–12 in XIV, 0–10 in XV, and 0–22 in XVI, dorsal pores absent, length 3.05–6.12 mm and width 4.6–6.07 mm. Prostomium epilobous. Setae minute, number 64–77 in VII, 73–89 in XX, and 19–26 between male pores in XVIII. First dorsal pore in 12/13. Spermathecal pores dorso-lateral, two pairs in intersegmental furrows of 7/8/9; distance between paired pores 0.36–0.39 body circumference dorsally apart, with one right and one left papillae immediately adjacent to each pore, within a dark-colored, diamond-shaped patch ( Fig. 2 A). Preclitellar genital papillae small, 1–7 in a transverse row in each of presetal and postsetal IX, closely along the setal line ( Fig. 2 B). Female pore single, mid-ventral in XIV. Male pores inconspicuous, paired in XVIII, 0.29–0.35 body circumference ventrally apart, each situated on a small, round porophore surrounded by 3–7 papillae, within a round or oval area enclosed by two or three skin folds ( Fig. 2 C). Postclitellar genital papillae 3–8 in a transverse row in each of presetal and postsetal XVIII, closely along the setal line. One specimen with additional pre- and postsetal papillae closely paired along the setal line in mid-ventrum of XIX. Preserved specimens dark brown or dark purplish brown on dorsum, grayish brown on ventrum, and dark brown on clitellum.

Internal: Septa 5/6–7/8 thick, 10/11–13/14 muscular, 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 XXIII–XXIV, each simple, distal end either straight or bent. Esophageal hearts in X–XIII. Spermathecae two pairs in VII and IX ( Fig. 2 D), or in VIII and IX, each with a peach-shaped or elongated oval-shaped ampulla 2.41–3.52 mm long and 1.16–2.86 mm wide, and a stout spermathecal stalk 0.85–1.15 mm in length. Diverticulum coiled with a short, straight, slender to stout proximal part. Accessory glands long- or short-stalked, mushroom-like, 0.9– 1.36 mm in total length, each corresponding to external genital papilla ( Fig. 2 D). Holandric, testes small, two pairs in ventrally joined sacs in X and XI. Seminal vesicles large, surface smooth, two pairs in XI and XII, anterior pair rectangular-shaped, extending anteriorly to the posterior half or the entire compartment of segment X, posterior pair transversely elongated oval-shaped, with a round dorsal lobe at the dorso-anterior end. Prostate glands large in XVI–XXII ( Fig. 2 E), divided into several lobules by grooves. Prostatic duct slender, slightly enlarged at distal end, C- or U-shaped in XVIII. Accessory glands around prostatic duct short-stalked, irregular-shaped, about 0.6 mm in total length; glands in mid-ventrum of XVIII mushroom-like, short- or long-stalked, 1.0– 1.3 mm in total length, corresponding to external genital papillae ( Fig. 2 E).

DNA barcodes. GenBank accession numbers KJ782570 (MTS 92, holotype), KJ782576 (MTS 19, paratype), KJ782569 , KJ782571 , and KJ782572 (MTS 31, 102 and 137, respectively).

Etymology. The name beiganensis is given to this subspecies with reference to its type locality, the island of Beigan.

Remarks, subspecies comparison. The two taxa, nanganensis and beiganensis, share most of the characters and are genetically closely related ( Fig. 3 ). However, they are easily distinguishable primarily in the arrangements of genital papillae: the papillae of A. nanganensis beiganensis are arranged in a single row at both sides of setal lines on mid-ventrum of segments IX and XVIII, whereas these papilla arrangements are absent in A. nanganensis nanganensis ( Table 2 ). Also, A. nanganensis nanganensis has a row or a cluster of 2–16 tiny papillae anterior to each spermathecal pore, while A. nanganensis beiganensis has one right and one left papillae immediately adjacent to each spermathecal pore. In addition, beiganensis is slightly larger and has higher setal number than nanganensis ( Table 2 ). A. nanganensis beiganensis was only found on the island of Beigan, whereas A. nanganensis nanganensis was collected from the island of Nangan only. While geographical isolation has led to morphological divergence and thus subspecific differentiation, there is almost no divergence of the COI sequences between nanganensis and beiganensis, suggesting that the divergence between the two subspecies is fairly recent and cannot be resolved by COI.

Species comparison. Amynthas nanganensis sp. nov. shares the following combination of characters with Amynthas polyglandularis ( Tsai, 1964) from northern Taiwan, Amynthas kinmenensis Shen et al., 2013 from Kinmen, and Amynthas hsiyinensis Shen et al., 2014 from the island of Hsiyin, Matsu: (1) two pairs of spermathecal pores in intersegmental furrows of 7/8/9, (2) numerous genital papillae, (3) coiled diverticulum, (4) large seminal vesicles, (5) large prostate glands, and (6) stalked accessory glands ( Table 2 ). Though these species are fairly similar, their number and position of papillae are species specific and distinctively different from those of A. nanganensis : A. polyglandularis has unique papilla arrangement with 10–23 papillae in transverse rows in presetal VIII and presetal IX, and 34–53 papillae in transverse rows in mid-ventral XVIII; A. kinmenensis has 9–24 papillae arranged in form of an arc stretching across two annulets and medial to each spermathecal pore, and 9–20 papillae in line with each male pore in presetal XIX; A. hsiyinensis has 10–20 papillae in a transverse row in each of postsetal VIII, presetal IX and presetal X, and about 140 papillae in transverse rows in mid-ventral XVIII ( Table 2 ).

Amynthas nanganensis Amynthas nanganensis Amynthas hsiyinensis Shen et Amynthas polyglandularis Amynthas kinmenensis Shen et nanganensis ssp. nov. beiganensis ssp. nov. al., 2014 ( Tsai, 1964) al., 2013

Locality Nangan, Matsu Beigan, Matsu Hsiyin, Matsu Northern Taiwan Kinmen

The close resemblance in both external and internal features among these species and the COI tree ( Fig. 3 ) suggest a great possibility that the four species evolved from a common ancestor and may have gone through allopatric speciation. Since Taiwan was connected by a landbridge to the Chinese mainland periodically during the Pleistocene ( Tsai et al. 2000; 2002), the differentiation of these species should have begun long before the last sea level change in the end of Pleistocene about 10,000 years ago. Based on geographical affinities, we highly expect to find related species in the neighboring Fujian Province of southeast China.

Figures

FIGURE 2. Amynthas nanganensis beiganensis ssp. nov. Holotype (TESRI-O-H- 44). A. Right-lateral view of right spermathecal pore region (gp, genital papilla; sp, spermathecal pore). B. Ventral view of segment IX. C. Ventral view of male pore region. D. Dorsal view of right spermathecae (shaded area) (amp, ampulla; dv, diverticulum; ag, accessory gland). E. Dorsal view of left prostate gland. Scale bars = 1 mm.

FIGURE 3. Neighbor-joining tree of representatives of Amynthas polyglandularis from Taiwan, Amynthas nanganensis nanganensis, Amynthas nanganensis beiganensis and other native Amynthas species from Matsu and Kinmen based on COI gene and Kimura’s two-parameter model, and rooted using Amynthas corticis. 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.

Tables

TABLE 2. A comparison of characters among Amynthas nanganensis nanganensis sp. et ssp. nov., Amynthas nanganensis beiganensis ssp. nov., Amynthas hsiyinensis, Amynthas polyglandularis and Amynthas kinmenensis.

Body length (mm)	81–145	103–186	85–145	134	110–276
Segment number	101–129	110–130	123–129	88	104–141
Weight (g)	0.63–1.89	1.66–3.66	1.11–3.12	–	0.67–5.32
First dorsal pore	12/13	12/13	12/13	12/13	12/13 or 13/14
Setal number
VII	54–70	64–77	69–74	64 or 65 (VIII)	47–69
XX	56–84	73–89	75–78	67–70 (XXV)	52–81
between male pores	18–25	19–26	20–27	20–21	11–22
Genital papillae
papilla adjacent to male pore preclitellar postclitellar Spermathecal pores	Surrounded by 6–17 papillae 2–16 anterior to each spermathecal pore Absent 7/8–8/9	Surrounded by 3–7 papillae 1–7 in a transverse row in each of presetal and postsetal IX, and 1 on either side of each spermathecal pore 3–8 in a transverse row in each of presetal and postsetal XVIII 7/8–8/9	One anteromedial and one posteromedial 10–20 in a transverse row in each of postsetal VIII, presetal IX and presetal X About 140 in transverse rows in mid-ventral XVIII 7/8–8/9	Surrounded by 4–9 papillae 10–23 in transverse rows in presetal VIII and presetal IX 34–53 in transverse rows in mid-ventral XVIII 7/8–8/9	Surrounded by 5–9 papillae 9–24 in form of an arc stretching across two annulets and medial to each spermathecal pore 3–8 adjacent to 17/18 and 9–20 in presetal XIX, in line with each male pore 7/8–8/9
Diverticulum	Coiled	Coiled	Coiled	Coiled	Coiled
Hearts	X–XIII	X–XIII	X–XIII	Last heart in XIII	X–XIII
Testes	Small in X, XI	Small in X, XI	Oval in X, XI	Small, both in XI	Small in X, XI
Seminal vesicles	Large	Large	Large	Large	Large
Prostate glands	Large in XVI–XXI	Large in XVI–XXII	Large in XVI–XXI	Large in XVI–XXI	Large in XVI–XXI
Prostatic ducts	U-shaped in XVIII	C- or U-shaped in XVIII	S- or U-shaped in XVIII–XIX	U-shaped in XVIII–XIX	C- or U-shaped in XVIII
Accessory glands	Stalked	Stalked	Stalked	Stalked	Stalked