Amynthas pavimentus Tsai CF and Shen, 2010

Tsai, Chu-Fa, Shen, Huei-Ping & Tsai, Su-Chen, 2010, Four new species of Amynthas earthworms (Oligochaeta: Megascolecidae) from the Central Mountain Range of southern Taiwan, Journal of Natural History 44 (21 - 22), pp. 1251-1267 : 1252-1256

Amynthas pavimentus Tsai CF and Shen , sp. nov.

( Figure 1 )

Type material

Holotype. Clitellate (mature) specimen (121 mm in length, dissected) collected 15 March 2000 along Road 20 near Hsiangyang (elevations 2100–2300 m), Taitung

County by C.F. Tsai, S.C. Tsai, H.P. Shen, S.T. Chang, H.S. Fang, H.P. Yang, and T.J. Lin (TESRI-O-H-31).

Paratypes. Two clitellates (same collection data as holotype, TESRI-O-P-26).

Other material

One clitellate collected 14 March 2000 along Meilan Forest Road (elevation 2000 m) off Road 20 near Meishan , Kaohsiung County (coll. no. 2000-12-Shen); one clitellate (dissected) collected 15 March 2000 along Road 20 near Likuan Bridge (elevation 2000 m), Kaohsiung County (coll. no. 2000-17-Shen); one clitellate and one aclitellate (immature) specimens collected 15 March 2000 along Road 20 near Kuaigu (elevation 2500 m), Kaohsiung County (coll. no. 2000-19-Shen); six clitellates (one dissected) and two aclitellates collected 15 March 2000 along Road 20 near Takuanshan-Yako Tunnel (elevation 2700 m) between Taitung and Kaohsiung counties (coll. no. 2000-20-Shen); four clitellates collected 15 March 2000 along Road 20 near Yako (elevation 2700 m), Taitung County (coll. no. 2000-21-Shen). All collections were made by collectors of the holotype .

Diagnosis

Small to medium; length (clitellates) 50–121 mm. Segments numbering 61–103. Setae 30– 41 in VII, 40–51 in XX, 8–13 between male pores. First dorsal pore in 5/6 or 6/7. Spermathecal pores four pairs in 5/6–8/9, 0.28–0.32 body circumference ventrally apart. Male pores 0.27–0.3 body circumference ventrally apart in XVIII, each on a round porophore surrounded by one to three shallow skin folds, with one to eight genital papillae at medioanterior and/or medio-posterior portion outside the skin folds. Genital papillae tiny, in transverse patches between setal line and intersegmental furrow, presetal in VIII–IX, XVIII–XIX and occasionally in XX, and postsetal in XVII–XVIII and occasionally in XIX. Spermathecae four pairs in VI–IX. Seminal vesicles two pairs in XI and XII. Prostate glands large, mostly in rectangular shape with follicular surface in XVI–XIX or XVII–XX. Prostatic duct short, C-shaped or U-shaped. Accessory glands stalked, corresponding to external genital papillae, each small with a round head and a slender stalk.

Description

External characters. Total length (clitellates) 50–121 mm. Weight 0.46–1.16 g. Segments numbering 61–103. Clitellum XIV–XVI, length 2.74–4.11 mm and width 1.98–3.96 mm. Prostomium epilobous. Setal number 30–41 in VII, 40–51 in XX, and 8–13 between male pores in XVIII. First dorsal pore in 5/6 or 6/7. Spermathecal pores four pairs, each small, lip-like elevation, in intersegmental furrows of 5/6–8/9, distance between paired pores 0.28–0.32 body circumference ventrally apart. Genital papillae tiny, round, tubercle-like, and highly variable in number and positions ( Table 1). Presetal papillae in transverse patches between setal line and intersegmental furrow; the number 5–37 in VIII and 5–40 in IX. No preclitellar papilla in the postsetal portion and in the vicinity of spermathecal pores ( Figure 1A ). Female pore single, mid-ventral in XIV.

Male pores paired in XVIII, 0.27–0.3 body circumference ventrally apart. Each pore on a round porophore about 0.35 mm in diameter, surrounded by one to three shallow skin folds, with one to eight genital papillae at medio-anterior and/or medioposterior portion outside the skin folds ( Figure 1B ). Postclitellar papillae similar in shape and size to those in the preclitellar region, also in transverse patches between male pores ( Figure 1B ); presetal papillae 20–61 in XVIII, 8–59 in XIX and 0–1 in XX; postsetal papillae 0–8 in XVII, 0–5 in XVIII and 0–3 in XIX ( Table 1).

Preserved specimens pinkish brown on head and dorsum, light brown on ventrum, and dark pinkish brown on clitellum.

Internal characters. Septa 5/6–7/8 and 10/11–13/14 thick, 8/9/10 missing. Nephridial tufts thick on anterior faces of 5/6/7. Gizzard large, round in VIII–X. Intestine enlarged from XV. Intestinal caeca paired in XXVII, extending anteriorly to XXIII– XXIV, each simple, slender, slightly folded with white end that bent toward the dorsum ( Figure 1F ). Oesophageal hearts in XI–XIII.

Spermathecae four pairs in VI–IX, varied in sizes and shapes ( Figure 1C ). Each with a round or oval-shaped ampulla 0.7–3.27 mm long and 0.4–2.18 mm wide, and a slender to stout spermathecal stalk 0.37–0.87 mm in length. Diverticulum with a small, oval-shaped seminal chamber and a slender stalk 0.6–1.0 mm in length, that is as long as or slightly longer than the spermathecal stalk.

Holandry. Testes two pairs in ventrally joined sacs in X and XI; first pair large. Vas efferens connected in XI on each side to form a vas deferens. Seminal vesicles two pairs in XI and XII, normal, medium-sized or large, occupying the full compartment, follicular surface with a round dorsal lobe ( Figure 1D ). Prostate glands large, mostly in rectangular shape with follicular surface in XVI–XIX or XVII–XX. Prostatic duct short, C-shaped or U-shaped ( Figure 1E ).

Accessory glands stalked, transparently white in colour, corresponding to external genital papillae; each gland small with a round head 0.15–0.47 mm long and a slender stalk 0.15–1.5 mm in length in both preclitellar and postclitellar regions ( Figure 1C,E ).

Etymology

The name pavimentus is given to this species to indicate the mosaic-like pavement of genital papillae in the mid-ventral portion.

Remarks

Amynthas pavimentus sp. nov. is an octothecate earthworm belonging to the diffringens (= corticis ) species-group of the genus Amynthas ( Sims and Easton 1972) . It has a unique character of genital papillae in transverse patches in both spermathecal and male pore regions ( Figure 1A,B ). It is endemic to the Central Mountain Range in southern Taiwan at elevations of 2000–2700 m. The body lengths and the number of genital papillae in the postclitellar region show a V-shaped cline with elevation; both peak at 2100–2300 m and decrease with the increase and the decrease in the elevation ( Table 1). To date, there have been more than 100 species reported in the corticis - group. However, only Amynthas evansi ( Beddard, 1900) from the Malay Peninsula was found to have numerous genital papillae. It has a row of eight papillae on each side in the intersegmental furrow of 7/8 ( Beddard 1900). The position and arrangement of genital papillae are distinctively different between A. pavimentus and A. evansi .

Amynthas pavimentus is easily distinguishable from the other three earthworms with multiple genital papillae reported from Taiwan, namely, Amynthas papulosus sauteri ( Michaelsen, 1922) , Amynthas tessellatus Shen et al., 2002 and Amynthas polyglandularis ( Tsai, 1964) . The former two species are sexthecate with three pairs of spermathecae in segments VI–VIII, whereas A. polyglandularis is quadrithecate with two pairs of spermathecae in segments VII and IX. The four species also vary in their geographical and altitudinal distributions in Taiwan: A. papulosus sauteri is distributed at elevations of 100–1000 m in northern, central and southern Taiwan, A. tessellatus is found at 700–3200 m in central Taiwan ( Shen et al. 2002), and A. polyglandularis at 100–1000 m in northern Taiwan ( Table 2).

Figures

Figure 1. Amynthas pavimentus sp. nov. Holotype (TESRI-O-H-31) (121 mm): (A) ventral view of spermathecal pore region (gp, genital papilla; sp, spermathecal pore); (B) ventral view of male pore region (mp, male porophore); (C) dorsal view of right spermathecae (amp, ampulla; dv, diverticulum; ac, accessory gland); (D) dorsal view of right seminal vesicles (sv) (dl, dorsal lobe); (E) dorsal view of right prostate gland; (F) dorsal view of right caecum.