Amynthas luridus Shen & Chang, 2019

Shen, Huei-Ping, Chang, Chih-Han & Chih, Wen-Jay, 2019, Two new earthworm species of the genus Amynthas (Oligochaeta: Megascolecidae) from central Taiwan, with comments on some recent species assignments in Amynthas and Metaphire, Zootaxa 4658 (1), pp. 101-123 : 104-106

Amynthas luridus Shen & Chang , sp. nov.

( Figure 1 )

Holotype: Clitellate (mature) specimen (97 mm in total length, dissected), from roadside ditches in Ruiyen Creek Nature Reserve , Nantou County, 24°06'47.99''N, 121°10'10.93''E, 1526 m asl, 15 April 2009, H.-P. Chen (TESRI- O-H-54; RY021).

Paratype: 1 aclitellate, from roadside slopes in Ruiyen Creek Nature Reserve , Nantou County, 24°06'35.85''N, 121°11'20.19''E, 2198 m asl, 26 March 2009, T.-J. Lin & D.-H. Chen (TESRI-O-P-48; RY020) .

Other material. 1 clitellate (dissected) and 5 aclitellates (one dissected) from Mt. Beidongyen, Nantou County, 1800 m asl, 8 December 1999, C.-F. Tsai, S.-C. Tsai, P.-H. Ho & H.-P. Shen (TESRI-O- 1999-29-6); 1 aclitellate from Mt. Beidongyen , Nantou County, 24°04'59.05''N, 121°08'12.18''E, 1817 m asl, 19 August 2005 , T.-L. Huang, I.-M. Hsiao & H.-P. Shen (TESRI-O- 2005-9-3); 1 clitellate (RY019, PCR failed) from roadside ditches in Ruiyen Creek Nature Reserve , Nantou County, 24°06'14.29''N, 121°10'34.01''E, 2195 m asl, 25 March 2009 , T.-J. Lin & D.-H. Chen (TESRI-O- 2009-6-5); 1 clitellate (RY018) from ditches around forestry station in Ruiyen Creek Nature Reserve , Nantou County, 24°06'29.76''N, 121°11'24.07''E, 2308 m asl, 25 March 2009 , M.-H. Shen (TESRI-O- 2009-7).

Diagnosis. Length (clitellates) 83–107 mm. Segments numbering 94–132. Setae 45–59 in VII, 49–65 in XX, 9–13 between male pores. First dorsal pore in 12/13. Clitellum XIV–XVI. Spermathecal pores four pairs in 5/6–8/9, 0.28–0.32 body circumference ventrally apart. Male pores 0.26–0.27 body circumference ventrally apart in XVIII, each on a round porophore about 0.5 mm in diameter, with an anterior and/or a posterior genital papillae. Additional papillae often widely paired in postsetal XVII or occasionally paired in presetal XIX. Spermathecae four pairs in VI– IX. Seminal vesicles vestigial, two pairs in XI and XII. Prostate glands lobed, paired in XVII–XIX. Prostatic ducts small, short, C-shaped in XVIII. Accessory glands sessile or stalked, corresponding to external genital papillae.

Description. External: Length (clitellates) 83–107 mm, weight 0.98–1.54 g in 95%ethanol. Segments numbering 94–132. Clitellum XIV–XVI, setae and dorsal pores absent, 2.83–4.22 mm in length and 3.47–4.38 mm in width. Prostomium epilobous. Three annuli (secondary segments) per segment in VI–XIII. Setal number 45–59 in VII, 49–65 in XX, and 9–13 between male pores in XVIII. First dorsal pore in 12/13. Spermathecal pores four pairs in intersegmental furrows of 5/6–8/9, distance between paired pores 0.28–0.32 body circumference ventrally apart, each pore small, often with a small papilla posteromedial and another anteromedial to each pore, papilla 0.25–0.3 mm in diameter ( Fig. 1A ). No other genital papillae in the preclitellar region. Female pore single, mid-ventral in XIV. Male pores inconspicuous, paired in XVIII, 0.26–0.27 body circumference ventrally apart, each situated on a round porophore about 0.5 mm in diameter. Genital papillae anterior and/or posterior to male pores, paired, in line with and smaller than male porophore. Additional papillae often widely paired in line with male porophore in postsetal XVII or occasionally paired in presetal XIX. For all 11 specimens examined, male pores with anterior and posterior papillae for two specimens and one of them (RY021) with an additional pair in postsetal XVII ( Fig. 1B ); male pores with anterior papillae for two specimens and one of them (RY020) with an additional pair in presetal XIX ( Fig. 1C ); male pores with posterior papillae for seven specimens and five of them with an additional pair in postsetal XVII. Each papilla round, with a slightly concave center, about 0.35 mm in diameter. Genital papillae absent in the mid-ventral region. Live worms white. Preserved specimens white and slightly darker on clitellum.

Internal: Septa 5/6–7/8 thick, 8/9/10 absent, 10/11 thick, 11/12–13/14 muscular. Nephridial tufts on anterior faces of 5/6/7. Gizzard large, round in VIII–X. Intestine enlarged from XVI. Intestinal caeca paired in XXVII, simple, extending anteriorly to XXIV or XXIII. Esophageal hearts paired in XI–XIII. Spermathecae four pairs in VI–IX ( Fig. 1D ), ampulla elongated oval-shaped, surface wrinkled, 1.26–1.45 mm long and 0.6–0.84 mm wide, spermathecal duct stout, 0.3–0.6 mm in length. Diverticulum stalk slender, seminal chamber rudimentary or absent, not iridescent, 0.8–1.32 mm in total length. Accessory glands sessile or stalked, 0.3–0.5 mm in total length, each corresponding to external genital papilla. Holandric. Testes small, round, two pairs in ventrally joined sacs in X and XI. Seminal vesicles vestigial, two pairs in XI and XII, occupying less than half of the segmental compartment. Prostate glands paired in XVII–XIX ( Fig. 1E ), wrinkled and lobed. Prostatic ducts short, small, C-shaped in XVIII. Accessory glands round, sessile, about 0.3 mm in diameter, corresponding to external genital papillae.

DNA barcodes. GenBank accession numbers MK 251504 (RY021, holotype), MK 251503 (RY020, paratype) and MK 251502 (RY018) ( Table 1 ).

Etymology. The name luridus refers to the white, pale body color of this species.

Remarks. The postclitellar genital papilla arrangement of Amynthas luridus sp. nov. looks somewhat similar to that of A. aquilonius from central Taiwan, Amynthas hongyehensis Tsai & Shen, 2010 and Amynthas amis Shen, 2012 from eastern Taiwan, and Amynthas dinghuensis Shen & Chih, 2016 from southwestern Taiwan. A. aquilonius has postclitellar papillae widely paired in line with male porophore in presetal and postsetal XVII–XX ( Tsai et al. 2001); A. hongyehensis has postclitellar papillae widely paired in line with male porophore in presetal XVIII–XX ( Tsai et al. 2010; Shen 2012); A. amis occasionally has a papilla antero-medial to each male porophore (Shen 2012); A. dinghuensis has postclitellar papillae widely paired in line with male porophore in postsetal XVII and presetal XIX ( Shen et al. 2016). These species are octothecal with four pairs of spermathecae in VI–IX (for an exception in A. hongyehensis see below). Their characters are compared in Table 2 . All four species are morphologically distinguishable from A. luridus : A. aquilonius is much smaller, and has fewer segments, lower setal number, anteriorly placed first dorsal pore in 6/7, large seminal vesicles and large prostate glands ( Tsai et al. 2001); A. hongyehensis is much larger, and has variable numbers of spermathecae from three pairs in VII–IX to four pairs in VI–IX with normal, iridescent diverticula, and large testes, large seminal vesicles and large prostate glands ( Tsai et al. 2010; Shen 2012); A. amis has fewer setae, preclitellar genital papillae but no postclitellar papillae, spermathecae with normal, iridescent diverticula, and large testes, large seminal vesicles and large prostate glands (Shen 2012); A. dinghuensis is much smaller, and has fewer setae, spermathecae with normal, iridescent diverticula, and large testes, large seminal vesicles and large prostate glands ( Shen et al. 2016). All these species are also genetically distinct ( Fig. 2 ). Additionally, the GenBank accession number of the holotype of A. amis reported in Shen (2012) was erroneous and should be corrected to JX 290409 .

The genital papilla arrangement in the male pore region of A. luridus is also similar to that of Amynthas oyamai ( Ohfuchi, 1937) from northern Japan, Amynthas morii (Kobayashi, 1938) from Korea, Amynthas dangi ( Thai, 1984) from Vietnam, and Amynthas nametensis Hong et al., 2018 from Laos. A. oyamai has a papilla antero-medial to each male porophore ( Ohfuchi 1937); A. morii has a papilla anterior to each male porophore ( Kobayashi 1938b); A. dangi has papillae widely paired in line with male porophore in presetal XVIII–XIX and a papilla medial to each male pore ( Thai 1984; Nguyen et al. 2016a); A. nametensis has papillae widely paired in line with male porophore in presetal XVIII–XIX ( Hong et al. 2018). Like A. luridus , A. oyamai and A. morii are also octothecal and have small or little developed seminal vesicles and small, short prostatic duct ( Ohfuchi 1937; Kobayashi 1938a, b). However, their characters of larger body size, lower setal numbers, absence of postclitellar genital papillae in XVII and XIX, and absent or poorly developed prostate glands are different from those of A. luridus ( Table 2 ). As to A. dangi , its characters of large body size (length> 300 mm), much higher setal numbers (59 setae in segment II and more than 100 setae per segment after segment VIII) and two pairs of spermathecal pores in 7/8/9 ( Thai 1984; Nguyen et al. 2016a) clearly separate it from A. luridus . The body size and setal numbers of A. nametensis are close to those of A. luridus , but A. nametensis is quadrithecal with two pairs of spermathecal pores in 7/8/9. Furthermore, A. nametensis has globular ampulla, diverticulum coiled into irregular ovate block, and prostate glands extending from XVII to XXIII with long, stout, coiled ducts ( Hong et al. 2018), whereas A. luridus has elongated oval-shaped ampulla, diverticulum with a slender stalk and a seminal chamber rudimentary or absent, and prostate glands in XVII–XIX with short, small, C-shaped prostatic ducts.

Figures

FIGURE 1. Amynthas luridus sp. nov. A. Ventral view of spermathecal pore region of Holotype (TESRI-O-H-54) (sp, spermathecal pore; gp, genital papilla). B. Ventral view of male pore region of holotype (mp, male porophore). C. Ventral view of male pore region of paratype. D. Dorsal view of right spermathecae of holotype (amp, ampulla; dv, diverticulum; ag, accessory gland). E. Dorsal view of right prostate gland of holotype (pd, prostatic duct). Scale bars = 1 mm.

FIGURE 2. Neighbor-joining tree of Amynthas luridus and representatives of Amynthas aquilonius Tsai et al., 2001, Amynthas catenus Tsai et al., 2001, Amynthas proasacceus Tsai et al., 2001, Amynthas hohuanmontis Tsai et al., 2002, Amynthas tessellatus Shen et al., 2002, Amynthas fenestrus Shen et al., 2003, Amynthas tantulus Shen et al., 2003, Amynthas uvaglandularis Shen et al., 2003, Amynthas hongyehensis Tsai & Shen, 2010, Amynthas amis Shen, 2012, and Amynthas dinghuensis Shen & Chih, 2016 from Taiwan. The tree is 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. Type materials are indicated in parentheses. Numbers around nodes are bootstrap values above 50.