Amynthas chaishanensis, James & Shih & Chang, 2005

James, Samuel W., Shih, Hsi-Te & Chang, Hsueh-Wen, 2005, Seven new species of Amynthas (Clitellata: Megascolecidae) and new earthworm records from Taiwan, Journal of Natural History 39 (14), pp. 1007-1028 : 1021-1022

Amynthas chaishanensis sp. nov.

( Figure 3F, G )

Holotype: adult collected at Chaishan , near National Sun Yat-sen University, Kaohsiung City, Taiwan 22 ° 399190N, 120 ° 169060E; 80 m, 30 September 1999, by H.- T. Shih, NMNS 4054-022 . Paratypes: three adults, same collection data as holotype, NMNS 4054-023 .

Etymology

This species is named after the locality Chaishan (5Mt. Chai), Kaohsiung City, Taiwan.

Description

Dimensions 203–228 mm by 8–11 mm at segment x, 6–9 mm at xxx, 8–11 mm at clitellum; body cylindrical throughout, segments 112–137. Setae regularly distributed around segmental equators, numbering 130–150 at vii, 126–138 at x, 104–120 at xxv, size and distance regular; setal formula AA:AB:YZ:ZZ52:1:1:3 at xxv. Prostomium epilobic, with tongue open. Dark purple-brown pigment on dorsalmost third, formalin preservation. First dorsal pore 12/13. Clitellum annular xiv–xvi; setae invisible externally.

Male pores on large alate porophores in shallow apical invagination, 0.33 circumference apart; 20 setae between male pores. Female pore single in xiv. Spermathecal pores dorsal, intrasegmental on small indistinct porophores in presetal annulus of triannulate segments vi–ix, 0.10 circumference apart ( Figure 3F ).

Septa 5/6/7/8 very thick, muscular, 8/9 present ventrally, 9/10 absent, 10/11–13/14 very thick, diminishing in muscularity posteriorly; gizzard viii, blood glands iv, v. Intestinal origin half xv; typhlosole simple fold one-third lumen diameter from xxvii. Intestinal caeca simple, long slender, originating in xxvii, extending anteriorly to xxv, xxiii, no incisions. Oesophageal hearts two pairs in xii–xiii; x, xi lacking, commissural vessels vii, ix lateral, viii to gizzard. Extraoesophageal vessels fuse to single vessel on ventral side of oesophagus in x.

Male sexual system proandric, testes, funnels in ventrally joined sacs in x. Seminal vesicles large in xi, with dorsal lobe, enclosed within sac containing all segmental contents. Prostates xviii, numerous deeply incised main lobes covering xvii–xx, ducts short, thick, muscular, straight; numerous ductlets from glandular portion form undivided fan-shaped array, ental portion of prostatic duct with approximately 40 very small lumens, one larger lumen probably sperm duct; vasa deferentia join at duct–glandular portion junction; vasa deferentia non-muscular.

Ovaries in xiii. Paired spermathecae in vi–ix; ampulla large ovate sac, duct stout but flaccid, half length of ampulla, diverticulum stalk long convoluted kinks enclosed within membrane, chamber terminal ovate knob; diverticulum axis shorter than ampulla axis ( Figure 3G ); no nephridia on spermathecal ducts.

Remarks

This proandric octothecal species with intrasegmental spermathecal pores keys to the rimosus -group in Sims and Easton (1972), all members of which are from Myanmar. Amynthas rimosus (Gates, 1931) is holandric and its spermathecal pores are ventral. The true affinities of A. chaishanensis lie with the other Taiwanese proandric species, and particularly with A. formosae . Amynthas chaishanensis has numerous prostatic ductlets of equal size joining the large prostatic ducts at the same point, creating a single undivided fan of ductlets. This is in contrast to the other species described here and A. formosae , all of whose ductlets gather into small bundles prior to joining the main prostatic duct.

Amynthas chaishanensis is one of two known proandric Amynthas species with dorsal intrasegmental pores on vi–ix, the other being A. formosae . It is further distinguished by having hearts only in xii and xiii but A. formosae ’s hearts are unknown, beyond having the last hearts in xiii. However, Gates (1959) noted the presence of hearts in x–xiii in his material and did not note this as a distinction between his material and A. formosae . Other differences from A. formosae are many more setae in the anterior segments, fewer setae between the male pores, slightly more widely spaced (from mid-dorsal line) spermathecal pores, caeca originating in xxvii, lack of pseudovesicles in xii and xiii, and prostate glands divided into numerous main lobes, rather than only 2.

Figures

Figure 3. (A) Left lateral view of segments i–ix and ventral view of Amynthas kaopingensis, with detail of male pore; (B) spermatheca of Amynthas kaopingensis; (C) dorsal view of segments i–x and ventral view of xiv–xix of Amynthas ailiaoensis; (D) left prostate gland of Amynthas ailiaoensis, showing numerous small ductlets (curved line traversing the gland is septum 17/18); (E) spermatheca of Amynthas ailiaoensis; (F) dorsal view of segments i–x and ventral view of xiii–xix, Amynthas chaishanensis (the dashed line on the dorsal view represents the mid-dorsal line); (G) spermatheca of Amynthas chaishanensis.