Amynthas samgaki, Hong, 2011

Hong, Yong, 2011, Two new species of Amynthas (Clitellata: Megascolecidae) from lettuce fields of Mt. Taebaek, Korea, Revue suisse de Zoologie 118 (2), pp. 223-230 : 226-229

Amynthas samgaki sp. n.

Figs 2 A-B

MATERIAL: Holotype; clitellate ( NIBRIV0000224642 ); Korea, Gangwon province, Taebaek municipality, Samsu-dong , Hasam 2-ri , Mt. Taebaek (37° 14.074’N, 128° 59.151’E), 600-800 m, soil and litter layers, 29 June 2006, Y. Hong coll. – Paratypes; 1 clitellate ( NIBRIV0000224643 ), 1 clitellate ( MHNG INVE 75338 ); same data as for holotype. – Nontype material; 1 clitellate specimen, Taebaek municipality, Samsu-dong , Hasam 2-ri , Mt. Taebaek (37° 14.074’N, 128° 59.151’E), 600-800 m, soil and litter layers, 4 July 2007, Y. Hong coll.

ETYMOLOGY: The species is named after Sim Samgak, whose farm is its type locality.

DIAGNOSIS: Paired spermathecal pores in 5/6, 6/7; male field with large eggshaped raised pads with transverse seminal groove across pad center, 2.5-3.0 mm distance between male pores, testes sacs ventral, paired.

DESCRIPTION: Dimensions 77-110.5 mm by 4.5-4.7 mm at segment X, 6. 0-6.5 mm at segment XXX, 5.5-6.5 mm at clitellum; segments 64-79. Setae regularly distributed around segmental equators, numbering 24-32 at VII, 52-63 at XX, 7 between male pores, setal formula AA:AB:ZZ:YZ= 2.5:2:2:2 at XIII. Female pore single in XIV, on 0.6-0.9 mm circle or oval. Prostomium epilobic with tongue open, clitellum coffee color, formalin preservation. First dorsal pore at 12/13. Clitellum annular XIV-XVI; setae invisible externally.

Male field with large egg-shaped raised pads, narrow end lateral, with transverse seminal groove from center of pad to just inside lateral edge, male pore at medial end of groove. Three to four concentric arcs around lateral end of pad, 2.5-3.0 mm distance between male pores. Paired spermathecal pores in 5/6 and 6/7, lateral, minute. Genital markings lacking.

Septa 5/6-7/8 thick, 8/9, 9/10 absent, 10/11-12/13 thickened. Gizzard large in VIII-X. Intestine begins in XV, lymph glands not found. Typhlosole medium sized from XXVI. Intestinal cecum originating in XXVII and extending anteriorly about to XXIV, bent down to ventral body wall, simple finger-shaped. Oesophageal hearts four pairs in X-XIII; X, XII and XIII large. Male sexual system holandric, testes and funnels in ventrally paired sacs in X-XI. Seminal vesicles two pairs in XI-XII medium sized. Prostates in XVIII, extending through XVII-XIX, long stout duct, glands divided into small lobes.

Ovaries in XIII. Paired spermathecae in VI, VII; each ampulla roughly ovate, flattened, wrinkled on surfaces, slender duct as long as ampulla; diverticulum chamber club-shaped, white; slender stalk as long as ampulla, no nephridia on spermathecae ducts. Genital marking glands not found.

REMARKS: Amynthas samgaki sp. n. keys to the morrisi group in Sims & Easton (1972), which is composed of 30 species. Chen (1933; 1936; 1938; 1946) recorded 12 species of the morrisi group from China. Among them, none has male pores on discs or similar pads. Amynthas oculatus ( Chen, 1938) has a large pair of postsetal genital papillae but the male pores lie outside these. Two species of the canaliculatus -group, A. jangbogoi and A. jindoensis, also have male discs with seminal grooves, and the pairs of spermathecal pores are intrasegmental on VI and VII, rather than in 5/6/7. In A. jangbogoi the disc is bowling-pin shaped. The spermathecal diverticulum stalk of the latter has numerous tight kinks, as opposed to straight. I include this comparison because the canaliculatus -group could include morrisi-group species with independently evolved intrasegmental spermathecal pores.

The following Korean morrisi -group species are known: A. fibulus fibulus (Kobayashi, 1936), A. fibulus ranunculus (Kobayashi, 1936), A. kobayashii (Kobayashi, 1938), A. koreanus (Kobayashi, 1938), A. geojeinsulae (Song & Paik, 1970), A. draconis Hong & James, 2001, A. naejangensis Hong & James, 2001, A. assimilis Hong & Kim 2002, and A. gyeryongensis Hong & Kim, 2002. Amynthas assimilis and A. naejangensis have male discs with seminal grooves. In A. assimilis the disc and groove are oriented diagonally. Amynthas naejangensis is larger and has more segments (116-153 mm vs 77-110 mm, 96-117 vs 64-79 respectively) but is very similar in most respects. The following details of A. naejangensis are to be contrasted to the description of Amynthas samgaki sp. n.: testes sacs dorsally united in X and XI, and enclosing seminal vesicles of XI, lymph glands present, male discs encroaching on adjacent segments, dorsal setal gap present, as indicated in the setal formula YZ:ZZ = 2.5:4. Clearly the two species are quite similar and could be regionally-differentiated descendants of a common ancestor.

Amynthas samgaki sp. n. is probably an endemic species, but more distributional and ecological data are needed to establish its relationships to soils and land use patterns. Further investigations are needed on its phylogenetic relationships with other Amynthas species, particularly A. naejangensis.

Figures

FIG. 2 Amynthas samgaki sp. n. (A) Ventral view. (B) Spermathecae and diverticulum. Scale bars = 4 mm (A), 2 mm (B).