Amynthas amplipapillatus Shen, 2012

Shen, Huei-Ping, 2012, Three new earthworms of the genus Amynthas (Megascolecidae: Oligochaeta) from eastern Taiwan with redescription of Amynthas hongyehensis Tsai and Shen, 2010, Journal of Natural History 46 (37 - 38), pp. 2259-2283 : 2274-2277

Amynthas amplipapillatus Shen , sp. nov.

( Figure 3 )

Type material

Holotype. Clitellate (67 mm in length, dissected) collected 27 September 2011 at Datong Village (elevation 931 m) along Shakadang Forest Road , Hsioulin , Hualien County by R. C. Jang and C.I. Chang (TESRI-O-H-37).

Paratype. One amputated clitellate collected 27 July 2011 along Wanrung Forest Road (elevation 675 m), Wanrung, Hualien County by M.H. Chen and C.I. Chang (TESRI- O-P-32) .

Other material

One clitellate collected 25 May 2011 along Jungping Forest Road (elevation 1170 m), Jhuohsi, Hualien County by S. T. Chang, M.H. Chen and C.I. Chang (coll. no. 2011-5); one clitellate (dissected) collected 8 June 2011 along Rueisuei Forest Road (elevation 575 m), Jhuohsi, Hualien County by S. T. Chang, M.H. Chen and C.I. Chang (coll. no. 2011-17); four clitellates (two dissected) collected 29 September 2011 along Hoping Forest Road (elevation 192 m), Hsioulin, Hualien County by R. C. Jang and C.I. Chang (coll. no. 2011-80); one amputated clitellate collected at Tzuchiang Bridge (elevation 133 m), Baliwan Village , Fongbin, Hualien County by H.P. Chen and C.I. Chang (coll. no. 2011-96) .

Diagnosis

Small to medium; length (clitellates) 67–101 mm. Segments numbering 90–129. Setae 44–61 in VII, 50–63 in XX, 0–12 on ventral XVI, and 9–11 between male pores. Spermathecal pores invisible. Male pores 0.24–0.3 body circumference ventrally apart in XVIII, each inconspicuous on an elongate transverse ridge of which the centre part slightly extending antero-posteriorly. Genital papillae widely paired in postsetal XVII and often in presetal XIX, and occasionally an additional pair in postsetal XIX. Each papilla large, round, 0.4–0.8 mm in diameter, slightly medial to the male porophore. Spermathecae usually absent (athecate). Seminal vesicles two pairs in XI and XII, each small, with a prominent and round or elongated oval dorsal lobe. Prostate glands paired and normal size to absent. Prostatic duct U-shaped or C-shaped. Accessory gland pad-like or mushroom-like, sessile or short-stalked, corresponding to each external genital papilla.

Description

External characters. Total length (clitellates) 67–101 mm. Weight 0.38–1.08 g. Segments numbering 90–129. Clitellum XIV– XVI, dorsal pores absent, 0–12 setae on ventral XVI, 1.84–3.45 mm in length and 2.97–3.9 mm in width. Prostomium epilobous. Setal number 44–61 in VII, 50–63 in XX, and 9–11 between male pores in XVIII. First dorsal pore in 11 / 12. Spermathecal pores absent. Genital papillae absent in the preclitellar region, but widely paired papillae in presetal VI and VII for paratype ( Figure 3A ). Female pore single, mid-ventral in XIV .

Male pores paired in XVIII, 0.24–0.3 body circumference ventrally apart. Each pore inconspicuous on an elongate transverse ridge, the centre part of the ridge slightly extending antero-posteriorly ( Figure 3B,C ). Genital papillae large, widely paired in postsetal XVII and often in presetal XIX, and occasionally an additional pair in postsetal XIX. Number and arrangement of papillae variable in different individuals: one pair only in postsetal XVII for three specimens; only one papilla on the left side in postsetal XVII for one specimen; one papilla on the left side in postsetal XVII and one pair in presetal XIX for one specimen; one papilla on the right side in postsetal XVII and one pair in presetal XIX for one specimen ( Figure 3B ); one pair in postsetal XVII, one pair in presetal XIX and one papilla on the left side in postsetal XIX for one specimen ( Figure 3C ); one pair in postsetal XVII, one pair in presetal XIX and one pair in postsetal XIX for one specimen; one pair in presetal XIX and one pair in postsetal XIX for one specimen. Each papilla round, 0.4–0.8 mm in diameter with concave centre, slightly medial to the male porophore. Rarely an additional pair of smaller genital papillae closely medial to the male porophore and posterior to the setal line in XVIII ( Figure 3C ), each papilla round, 0.35–0.45 mm in diameter with concave centre .

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

Internal characters. Septa 5 / 6–7 / 8 and 10 / 11–13 / 14 thick, 8 / 9 / 10 absent. Nephridial tufts thick on anterior faces of 5 / 6 / 7. Gizzard large, round in VIII–X. Intestine enlarged from XVI. Intestinal caeca paired in XXVII, extending anteriorly to XXII– 1 / 2XXV, each simple, slightly folded, the end straight or bent. Oesophageal hearts in XI–XIII.

Spermathecae absent, but a single spermatheca in left VII for holotype. The spermatheca small, with an oval ampulla of 0.68 mm long and 0.4 mm wide, and a long spermathecal stalk 0.7 mm in length. Diverticulum with a small, round seminal chamber and a slender stalk 0.7 mm in length, the same length to spermathecal stalk ( Figure 3D ).

Holandry: testes small or large, two pairs in ventrally joined sacs in X and XI. Vas efferens connected in XII on each side to form a vas deferens. Seminal vesicles two pairs in XI and XII, each small, about one-half to two-thirds of the segmental compartment, with a prominent and round or elongated oval dorsal lobe ( Figure 3E ). Prostate glands variable in size from normal in XVI–XIX ( Figure 3F ) to absent ( Figure 3G ), lobed with follicular surface. Prostatic duct U-shaped, distal end enlarged in XVII–XVIII ( Figure 3F ), or short, C-shaped in XVIII ( Figure 3G ). Accessory gland pad-like or mushroom-like, sessile or short-stalked, 0.32–0.45 mm wide, corresponding to each external genital papilla ( Figure 3F,G ).

Etymology

The name amplipapillatus is given to this species with reference to its large, paired genital papillae in the male pore region.

Remarks

Amynthas amplipapillatus sp. nov. is endemic to eastern Taiwan at elevations of 130–1170 m. It has large genital papillae widely paired in postsetal XVII and often in presetal XIX, and occasionally an additional pair in postsetal XIX. Similar papillar arrangements can also be found for Amynthas mutus ( Chen, 1938) and Amynthas tetrapapillatus Quan and Zhong, 1989 from Hainan Island, Amynthas fluxus ( Chen, 1946) from Sichuan, China, Amynthas micronarius (Goto and Hatai, 1898) from Japan, and Amynthas obtusus ( Ohfuchi, 1957) from the Ryukyu Islands. Both A. micronarius and A. obtusus are octothecate with setal numbers 26–39 in VII and 33–51 in XX for the former ( Ohfuchi 1937), and 33–37 in VII and 43–50 in XX for the latter ( Ohfuchi 1957). Amynthas fluxus is sexthecate with three pairs of spermathecal pores in 5 / 6–7 / 8 and 73 and 70 setae in VIII and XXV, respectively ( Chen 1946). Amynthas tetrapapillatus is bithecate with a pair of spermathecal pores near the dorso-median line in 5 / 6; it is much larger with body length 152–165 mm long and has much higher setal number (93–107 in VII and 86–102 in XX) ( Quan and Zhong 1989). Amynthas amplipapillatus is easily distinguishable from the above four species. As for A. mutus , its body size (50–80 mm in length and 85–135 segments) and setal number (41–68 in VIII and 32–44 in XXV) are fairly similar to A. amplipapillatus . However, A. mutus has one small papilla in XIX behind each male pore, occasionally another pair in XVII in line with those in XIX, one pair of spermathecal pores in dorso-lateral 5 / 6 and hearts in X–XIII ( Chen 1938).

To date among the 49 endemic earthworms reported from Taiwan, eight of them show reproductive organ degeneration. They are Amynthas swanus (Tsai, 1964) with two to three pairs of spermathecae from northern and central Taiwan, Amynthas catenus Tsai et al., 2001 and Amynthas hohuanmontis Tsai et al., 2002 with zero to three pairs of spermathecae from central Taiwan, Amynthas shinanmontis Tsai and Shen, 2007 with zero to three pairs of spermathecae from southern Taiwan, the nearly athecate Amynthas chilanensis Tsai and Tsai, 2007 from northeastern Taiwan, the athecate Amynthas bilineatus Tsai and Shen, 2007 from central Taiwan, and Amynthas mutabilitas sp. nov. and Amynthas amplipapillatus sp. nov. from eastern Taiwan in this study. Amynthas catenus and A. hohuanmontis have been proved to be parthenogenetic through histological and molecular studies ( Shen et al. 2012). Furthermore, A. catenus was found to be polyploid with 2 n = 112 and 3 n = 168 ( Shen et al. 2011). It remains to be investigated whether polyploidy is common in these pheretimoid earthworms.

Figures

Figure 3. Amynthas amplipapillatus sp. nov. (A) Ventral view of preclitellar region of paratype (TESRI-O-P-32) (gp, genital papilla); (B) ventral view of male pore region of holotype (TESRI- O-H-37) (mp, male porophore); (C) ventral view of male pore region of paratype; (D) dorsal view of spermatheca in VII of holotype (amp, ampulla; dv, diverticulum); (E) dorsal view of right seminal vesicles (sv) of holotype (dl, dorsal lobe); (F) dorsal view of right prostate gland of holotype (ag, accessory gland); (G) dorsal view of left prostatic duct of a 90-mm clitellate (coll. no. 2011-17). Scale bar 1 mm.