Amynthas mutabilitas 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 : 2267-2274

Amynthas mutabilitas Shen , sp. nov.

( Figure 2 )

postclitellar Absent Absent to one pair Absent Absent Absent widely paired presetal in XVII and XIX

Hearts XI–XIII XI–XIII (vestigial X–XIII ∗ XI–XIII † X–XIII or absent in X †)

Spermathecae Normal, iridescent Absent, vestigial to Vestigial to normal Small, Small ampulla normal diverticulum and long absent diverticulum

Testes Large Large − − Moderate in size

Seminal vesicles Large Less developed Small Less developed Small

Prostate glands XVI–XX Absent, vestigial to Absent Absent or poorly Absent XVI–XX developed

Prostatic ducts C-shaped in XVIII Absent or C- or U-shaped in XVIII Short, C- or Small, short or U-shaped in U-shaped in S-shaped in XVII–XVIII XVIII XVIII †

Accessory glands Short-stalked in − Whitish ∗ − Large, stalked in spermathecal spermathecal region region

Absent

XI–XIII

Normal

Large

Small

Absent or vestigial

−

Round, compact with a short duct in XVIII

∗ Data from the original description of Beddard (1892).

† Data from Kobayashi (1938a).

Type material

Holotype. Clitellate (104 mm in length, dissected) collected 19 October 2010 along the Hongshih Forest Road (elevation 750 m) near Guanshan , Taitung County by R. C. Jang, M.H. Chen and L.H. Chen (TESRI-O-H-36).

Paratypes. Two clitellates [one dissected (voucher number: East 170)] and an aclitellate collected 26 May 2011 along the Walami Trail (elevation 750–840 m), Jhuohsi , Hualien County by S. T. Chang, M.H. Chen and C.I. Chang (TESRI-O-P-31) .

Other material

Thirty-three clitellates (two dissected) and an aclitellate collected 16 March 2000 along Road 20 near Wulu (elevation 713 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 (coll. no. 2000-24); four clitellates (one dissected) collected 16 March 2000 along Road 20 near Hsinwu (elevation 412 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 (coll. no. 2000-25); seven clitellates (two dissected) and three aclitellates collected 16 March 2000 along the Yenping Forest Road (elevation 1000 m) near Hongyeh Village, 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 (coll. no. 2000-27); three clitellates and an aclitellate collected 16 March 2000 along the Yenping Forest Road (elevation 950 m) near Hongyeh Village, 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 (coll. no. 2000-28); two clitellates collected 15 September 2005 along Road 20 near Wulu (elevation 713 m), Taitung County by H.P. Chen, I.M. Hsiao and S.T. Chang (coll. no. 2005-34); four clitellates [one dissected (voucher number: East 35)] and an aclitellate collected 13 April 2010 from Coastal Mountains Cycas taitungensis Nature Reserve (elevation 490 m), Taitung County by R.C. Jang, M.H. Chen and L.H. Chen (coll. no. 2010-6) (voucher numbers of specimens used for DNA barcoding analyses: East 8, 35); an aclitellate collected 13 July 2010 from Coastal Mountains Cycas taitungensis Nature Reserve (elevation 515 m), Taitung County by H.P. Chen and C.I. Chang (coll. no. 2010-39) (voucher number: East 37); four clitellates [two dissected (voucher number of one of them used for DNA barcoding analyses: East 61)] and three aclitellates collected 18 October 2010 from Coastal Mountains Cycas taitungensis Nature Reserve (elevation 490 m), Taitung County by R.C. Jang, M.H. Chen and L.H. Chen (coll. no. 2010-59) (voucher numbers of specimens used for DNA barcoding analyses: East 61, 63); one clitellate (dissected) collected 19 October 2010 along the Hongshih Forest Road (elevation 1280–1354 m) near Guanshan, Taitung County by R.C. Jang, M.H. Chen and L.H. Chen (coll. no. 2010-60); two clitellates and an aclitellate collected 19 October 2010 along the Hongshih Forest Road (elevation 1023 m) near Guanshan, Taitung County by R.C. Jang, M.H. Chen and L.H. Chen (coll. no. 2010-62); three clitellates (one dissected) and an aclitellate (same collection data as holotype) (coll. no. 2010-63); three clitellates [one dissected (voucher number: East 106)] collected 20 October 2010 along the Yenping Forest Road (elevation 1170–1274 m) near Hongyeh, Taitung County by R.C. Jang, M.H. Chen and L.H. Chen (coll. no. 2010-67); one clitellate [dissected (voucher number: East 117)] collected 20 October 2010 along the Yenping Forest Road (elevation 871–942 m) near Hongyeh, Taitung County by R.C. Jang, M.H. Chen and L.H. Chen (coll. no. 2010-68); two clitellates collected 26 May 2011 along the Walami Trail (elevation 628–742 m), Jhuohsi, Hualien County by S.T. Chang, M.H. Chen and C.I. Chang (coll. no. 2011-11); 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 (coll. no. 2011-46); four clitellates (one dissected) collected 26 October 2011 near Nanhsi (elevation 620 m), Changbin, Taitung County by H.P. Chen and C.I. Chang (coll. no. 2011-94).

Diagnosis

Small to medium; length (clitellates) 64–127 mm. Segments numbering 72–110. Setae 35–48 in VII, 44–53 in XX, and 5–8 between male pores. First dorsal pore in 11 / 12 or 12 / 13. Spermathecal pores invisible to two pairs in 5 / 6 / 7, 0.29–0.37 body circumference ventrally apart. Male pores 0.19–0.3 body circumference ventrally apart in XVIII, each on a papilla-like porophore with a genital papilla anterior to it, or on a flat-topped papilla-like porophore, with a genital papilla on or slightly behind the setal line immediately medial to it and another anterior or antero-medial to it. Genital papillae absent or paired in presetal VI–VIII. In addition, one papilla in line with or slightly medial to the right, left or each male pore in presetal XIX for about half of the specimens. Spermathecae absent to two pairs in VI and VII. Seminal vesicles two pairs in XI and XII, small to large, occupying half to full segmental compartment. Prostate glands from large in XVI–XXI to vestigial in XVIII only. Prostatic duct long, U-shaped. Accessory glands stalked in preclitellar region, and sessile or stalked in the postclitellar region, corresponding to external genital papillae.

Description

External characters. Total length (clitellates) 64–127 mm. Weight 0.52–1.55 g. Segments numbering 72–110. Clitellum XIV–XVI, setae and dorsal pores absent, length 1.63–3.59 mm and width 2.8–4.24 mm. Prostomium epilobous. Setal number 35–48 in VII, 44–53 in XX, and 5–8 between male pores in XVIII. First dorsal pore in 11 / 12 or 12 / 13. Spermathecal pores invisible to two pairs in intersegmental furrows of 5 / 6 / 7; distance between paired pores 0.29–0.37 body circumference ventrally apart. Preclitellar genital papillae usually paired in presetal VII or VI–VII ( Figure 2A ), in presetal VII and VIII for one specimen, and in postsetal VI for an amputated specimen ( Figure 2B ). Each papilla round, 0.3–0.5 mm in diameter, present in more than half of the specimens but totally absent in the others. Female pore single, mid-ventral in XIV.

Male pores paired in XVIII, 0.19–0.3 body circumference ventrally apart. Two types of arrangement of genital papillae in the male pore area for this species: (1) male pore situated on a papilla-like porophore with a genital papilla 0.25–0.45 mm in diameter anterior to it, surrounded by three or four skin folds ( Figure 2C ); (2) male pore on a flat-topped papilla-like porophore, with a genital papilla on or slightly behind the setal line immediately medial to it and another anterior or antero-medial to it, surrounded by three or four skin folds ( Figure 2D ). The two types of papillar arrangements can be observed in the same individual ( Figure 2E ). In addition, one papilla in line with or slightly medial to the right, left or each male pore in presetal XIX for about half of the specimens. Four papillae arranged transversely in presetal XVIII and XIX for one specimen ( Figure 2E ). Each papilla round, 0.3–0.45 mm in diameter with concave centre.

Preserved specimens dark brown on dorsum, light brown on ventrum, and brown to dark 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 in VIII–X. Intestine enlarged from XVI. Intestinal caeca paired in XXVII, extending anteriorly to XXIII–XXV, each simple, distal end either straight or bent. Oesophageal hearts in XI–XIII.

Spermathecae absent (athecate) to two pairs in VI and VII (quadrithecate), each with a round or oval-shaped ampulla of 0.82–2.15 mm long and 0.45–1.55 mm wide, and a long, slender to stout spermathecal stalk 0.35–1.7 mm in length. Diverticulum with an iridescent, oval-shaped seminal chamber of 0.38–0.85 mm long and a slen- der stalk of 0.9–1.5 mm in length ( Figure 2F ). Accessory gland long-stalked or short-stalked, 0.45–1.35 mm in length, each corresponding to external genital papilla ( Figure 2F ).

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 small to large, two pairs in XI and XII, folliculated with a round or elongated oval dorsal lobe, large vesicle occupying full segmental compartment while small vesicle about half of the segmental compartment. Prostate glands from large in XVI–XXI ( Figure 2G ), normal in XVII–XIX ( Figure 2H ), small in XVII–XVIII ( Figure 2I ), to vestigial in XVIII only ( Figure 2J ), wrinkled and lobed. Prostatic duct long, Ushaped in XVII–XVIII, distal end enlarged. Accessory glands round, sessile, or stalked of 0.35–1.4 mm in length, corresponding to external genital papillae ( Figure 2G–J ).

DNA barcodes

GenBank accession numbers JX290412 (East 170, dissected paratype), JX290426 , JX290418 , JX290420 , JX290423 , JX290424 , JX290402 and JX290405 (East 8, 35, 37, 61, 63, 106 and 117, respectively) .

Etymology

The name mutabilitas is given to this species to indicate its variable numbers of spermathecae and arrangement of its genital papillae in the male pore region.

Remarks

Amynthas mutabilitas sp. nov. is found on the east slope of the Central Mountain Range and Coastal Mountain Range at elevations of 410–1350 m in eastern Taiwan. It is morphologically fairly similar to Amynthas morrisi ( Beddard, 1892) . Amynthas morrisi is a quadrithecate earthworm belonging to the morrisi species-group of the genus Amynthas ( Sims and Easton 1972) . It has setae on ventral side of XVI, 12–16 setae between male pores, prostate glands in XVIII–XX or XVIII–XXI, and prostatic duct slender and coiled at distal end ( Chen 1931, 1933). However, A. mutabilitas has variable numbers of spermathecae from zero to two pairs in VI–VII, no setae on clitellum for fully matured individuals, five to eight setae between male pores, prostate glands from large in XVI–XXI to vestigial in XVIII, and distal end of prostatic duct straight and enlarged. The arrangement of genital papillae in the male pore area of A. mutabilitas is also similar to that of quadrithecate Amynthas ultorius ( Chen, 1935) from Hong Kong, but the latter has two pairs of spermathecal pores in 7 / 8 / 9 ( Chen 1935) and so belongs to the aeruginosus species-group ( Sims and Easton 1972).

Like A. mutabilitas , Amynthas varians ( Chen, 1938) from Hainan Island also has variable numbers of spermathecae from totally absent to two pairs in VI–VII. The two species can be easily distinguished by their male pore structure and genital papillar arrangements. The characteristics of long penis on a small tubercle in the male pore area, and one presetal and one postsetal rows of genital papillae in XVI–XVIII and VII–VIII of A. varians ( Chen 1938) are distinctly different from those of A. mutabilitas .

Figures

Figure 2. Amynthas mutabilitas sp. nov. (A) Ventral view of spermathecal pore region of holotype (TESRI-O-H-36) (gp, genital papilla; sp, spermathecal pore); (B) ventral view of preclitellar region of an amputated clitellate (coll. no. 2010-59); (C) ventral view of male pore region of holotype (mp, male porophore); (D) ventral view of male pore region of the dissected paratype (TESRI-O-P-31) (voucher number: East 170); (E) ventral view of male pore region of a 115-mm clitellate [dissected (voucher number: East 117), coll. no. 2010-68]; (F) dorsal view of left spermathecae of holotype (amp, ampulla; dv, diverticulum; ag, accessory gland); (G) dorsal view of left prostate gland of an amputated clitellate (coll. no. 2010-60); (H) dorsal view of left prostate gland of a 77-mm clitellate (coll. no. 2011-12); (I) dorsal view of left prostate gland of a 100-mm clitellate (coll. no. 2000-27); (J) dorsal view of left prostate gland of a 115-mm clitellate (coll. no. 2010-68). Scale bar 1 mm.