Amynthas dandongensis Han & Zhao 2026, sp. nov.

Amynthas dandongensis Han & Zhao sp. nov. Fig. 1 Type material. Holotype: • 1 clitellate (533 R 57_01) from Jinjiangshan Park, Dandong Prefecture, Liaoning (40.1312°N, 124.3746°E, 40 m elev.), China, collected by Huifeng Zhao, Yanmeng Bi and Shixiong Ma, 2023-07-26. Paratypes: • 13 clitellates (533 R 58_01, 02; 533 R 60_01, 02; 533 R 62_01 -04; 533 R 63_01; 533 R 64_01 -03) with the same information with as the holotype. All the specimens of the new species have been deposited in Langfang Normal University, Hebei, China (C-HLU). Diagnosis. Small worm with size 41–57 mm by 1.0– 2.5 mm (clitellum width). Segment numbers 86–104. Spermathecal pores four pairs, 5 / 6–8 / 9, medio-ventral, nearly inconspicuous. Spermathecae four pairs in VI – IX, ampulla oval; ampulla duct thick and stout, abruptly narrower towards ectal end; diverticulum with slender and long duct and ovoid receptacle; receptacle 1 / 3 length of the diverticulum duct. Diverticulum is the same length or slightly longer than the main pouch. Intestinal caeca simple, originating in XXVII extending anteriorly to XXI. Male pores and genital markings absent. Description. External characters. Length 41–57 mm, clitellum width 1.0– 2.5 mm, narrower toward pre-clitellar region (n = 5). Color of preserved specimens may vary from shades because of the duration of preservation but generally dorsum region is brown to yellowish brown, while ventrum part is pale yellow. Segment numbers 86–104. Prostomium epilobous (Fig. 1 A). First dorsal pore on 12 / 13. Clitellum pale brown, annular and raised at XIV – XVI; setae or dorsal pores and intersegmental furrow absent. Setal arrangement perichaetine; setae number 32–35 (V), 34–37 (VII), 40–45 (XIII), 48–52 (XX). Spermathecal pores four pairs, 5 / 6–8 / 9, medio-ventral, nearly inconspicuous with 0.20–0.22 C apart ventrally. Male pores, pre-clitellar and post-clitellar genital markings absent (Fig. 1 B). Female pore single, circular in a slightly concave porophore medioventral at XIV (Fig. 1 C). Internal characters. Septa 5 / 6 / 7 slightly thickened, 7 / 8 thin, 8 / 9 / 10 absent, 10 / 11 / 12 / 13 / 14 thin. Gizzard within VIII – X, large and barrel-shaped (Fig. 1 F). Intestine enlarged from XV. Intestinal caeca are simple, originating in XXVII and extending anteriorly to XXI (Fig. 1 E). Esophageal hearts three pairs in X – XIII. Spermathecae four pairs in VI – IX. Ampulla oval; ampulla duct thick and stout, abruptly narrower towards ectal end (1.3–1.8 mm long); diverticulum with slender and long duct and ovoid receptacle (1.5–2.0 mm long); receptacle 1 / 3 length of the diverticulum duct. Diverticulum is the same length or slightly longer than the ampulla plus duct (Fig. 1 D). Male sexual system holandric, testes sac well-developed, two pairs in X and XI. Seminal vesicles, two pairs in XI and XII. Prostate glands and accessory glands absent. Distribution in China. Liaoning Province, Northeast China. Habitat. Forest / Urban Park. Etymology. The specific name refers to the type locality, Dandong Prefecture; adjective. Remarks. Amynthas dandongensis sp. nov. belongs to the A. corticis species group (previously named the “ diffringens ” species group), characterized by having four spermathecal pores in 5 / 6 / 7 / 8 / 9. There was a total of 99 recorded species in the species group before 1972 (Sims and Easton 1972). Several species have been categorized as junior synonyms of A. corticis Kinberg, 1867, such as A. diffringens (Baird, 1869), A. divergens divergens (Michaelsen, 1892), A. yunnanensis (Stephenson, 1912) and A. heterochaetus (Michaelsen, 1891) by Blakemore (2004). Subsequently, an addition of 47 species / subspecies were reported: 12 species / subspecies were described from mainland China (Chen et al. 1975; Chen and Xu 1977; Sun et al. 2013; Sun et al. 2018; Dong et al. 2019; Li et al. 2024; Jin et al. 2024), eight species from Hainan Island China (Sun et al. 2012, 2013), 17 species from Taiwan Island China (Tsai et al. 2001; James et al. 2005; Chang et al. 2007; Tsai et al. 2007, 2010; Wang and Shih 2010; Shen 2012; Shen et al. 2013, 2014, 2019), eight species from South Korea (Hong and James 2001; Hong and Kim 2002; Blakemore 2012; Blakemore and Lee 2013), and three species from Laos (Hong et al. 2024). Table 2 presents a comparison of some members of the A. corticis species group in China with similar or overlapping sizes. The new species, aside from its lack of male pores, prostate glands, and genital markings, is unique from the rest of the members of the group by having a smaller body size (41–57 by 1.0–2.5); the first dorsal pore on 12 / 13 (vs 10 / 11 in A. meishanensis Chang, Lin, Chen, Chung & Chen, 2007; 5 / 6 in A. nanshanensis Shen, Tsai & Tsai, 2003, A. taoyuanensis Qiu & Jin, 2024 and A. libratus Tsai & Shen, 2010; 5 / 6 or 6 / 7 in A. pavimentus Tsai & Shen, 2010 and A. penpuensis Shen, Tsai & Tsai, 2003; pore-like marking on 7 / 8 in A. manicatus decorosus (Gates, 1932); 13 / 14 in A. tortuosus Qiu & Dong, 2019; rectangular gizzard in VIII – X (vs VII – X in A. meishanensis, A. pavimentus and A. libratus; IX – X in A. nanshanensis and A. penpuensis and A. taoyuanensis); and having simple intestinal caeca in XXVII – XXI (vs simple in XXVII – XXIV in A. meishanensis, A. taoyuanensis and A. tortuosus; XXVII – XXV in A. nanshanensis; XXVII – XXIII (XXIV) in A. pavimentus and A. libratus; XXVII – XXV (or XXIV) in A. penpuensis; compound, XXVII – XXII or XXIII in A. manicatus decorosus. Amynthas recavus Yuan & Zhang, 2019 also possesses dorsal pore on 12 / 13 yet with a larger size than the new species, and also possesses male pores and genital markings. Generally, the obvious distinction of the new species among other members of the A. corticis species group, regardless of the overlapping body sizes and dorsal pore on 12 / 13 is its lack of male pores and genital markings, which are typical among the other members of the group. The new species is morphologically most similar to A. sangumburi (Hong & Kim, 2002) from Jeju Island, South Korea (Table 3) in terms of size range (41–57 mm by 1.0– 2.5 mm in A. dandongensis sp. nov. and 46–68 mm by 2.3–2.5 mm in A. sangumburi); and having an ovate-shaped ampulla, intestinal origin in XV, and lacking genital markings. However, all the collected specimens of the new species lack male pores and prostate glands (vs present, centered on 0.8 mm circular flat porophores extending to lateral margins of ventrum in XVIII with prostate glands large within XVII – XX in A. sangumburi); and have more segments (86–104 vs 58–79). In addition, a previously recorded species from northeastern China, A. carnosus (Goto & Hatai, 1899), with four pairs of spermathecae in 5 / 6–8 / 9, differs from the new species in the body size, spermathecae shape, genital markings, and the male pore region. Currently, no other known species is morphologically similar to A. dandongensis sp. nov.