Amynthas hasamensis, 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 : 224-226

Amynthas hasamensis sp. n.

Figs 1 A-B

MATERIAL: Holotype; clitellate ( NIBRIV0000224640 ); Korea, Gangwon province, Taebaek municipality, Samsu-dong, Hasam 2-ri , Mt. Taebaek (37° 14.074’N, 128° 59.151’E), 600-800 m, fields cleared for cultivation by burning, soil and litter layers, 29 June 2006, Y. Hong coll. – Paratypes: 1 clitellate ( NIBRIV0000224641 ), 1 clitellate ( MHNG INVE 75339 ); same data as for holotype. – Nontype material; 2 clitellate specimens, Taebaek municipality, Samsudong , 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 for Hasam 2-ri, its type locality.

DIAGNOSIS: Three pairs of spermathecal pores in 5/6-7/8; male discs each with two transverse low ridges, short diagonal seminal groove between ridges, no other genital markings.

DESCRIPTION: Dimensions 80-130 mm by 5.5-6.5 mm at segment X, 6. 0-6.5 mm at segment XXX, 6.0-8.0 mm at clitellum; body cylindrical, segments 59-109. Setae regularly distributed around segmental equators numbering 31-35 at VII, 63-66 at XX, 0 between male pores, setal formula AA:AB:ZZ:YZ= 2:2:4:3 at XIII. Female pore single in XIV, within 0.8-1.0 mm circular porophore. Prostomium epilobic with tongue open, clitellum coffee color, formalin preservation. First dorsal pores at 12/13, one individual 11/12. Clitellum annular XIV-XVI; setae invisible externally.

Male field composed of paired male discs, each approximately ovate with longer axis transverse; each disc with two narrow transverse ridges, one equatorial, centered to slightly lateral of center on disc; one on posterior margin of disc, almost as long as long axis of disc. Surface between ridges and within outer margins of discs generally depressed; midventral gap between discs even more depressed. Seminal grooves short, from just posterior to medial end of equatorial ridge, diagonally posterior, lateral in a short arc convex anterior-laterally across depressed area between ridges to meet posterior ridge. Male pores at medial ends of seminal grooves, close to equatorial ridges, 0.15 circumference apart. Spermathecal pores in 5/6-7/8, 0.16 circumference apart, each with small tongue-like appendage within furrow; thickened lips immediately adjacent to each pore; ventral surface of VI-VIII thickened, slightly rugose, faintly pigmented.

Septa 5/6-7/8 thick, 8/9/10 absent, 10/11-13/14 thinly muscular. Gizzard large in VIII-X. Intestine begins in XV; lymph glands not found. Typhlosole medium sized from XXVI. Intestinal caeca originating in XXVII and extending anteriorly about to XXII, simple finger-shaped sac. Oesophageal hearts three pairs in XI-XIII; X, only one side. Male sexual system holandric, testes and funnels in ventrally joined sacs in X-XI. Seminal vesicles two pairs in XI-XII medium sized with dorsal lobes. Prostates in XVIII, extending over XVI-XIX, stout ducts, both glands consist of two main lobes, each divided again into many small lobes.

Ovaries in XIII. Paired spermathecae in VI-VIII, VI smallest; ampulla surface wrinkled egg-shaped, duct slender, shorter than ampulla, diverticulum chamber clavate, almost transparent with slender stalk shorter than ampulla, no nephridia on spermathecal ducts. Genital marking glands not found.

REMARKS: In Sims & Easton (1972), Amynthas hasamensis sp. n. keys to the hawayanus (gracilis) group. The new species is not A. gracilis (Kinberg 1867) or its possible and actual synonyms ( Blakemore, 2003), all of which have several small genital markings in the spermathecal and male field segments, and lack the large porophores with seminal grooves. The gracilis species group includes 13 species found in Korea and/or Japan: A. acinctus (Goto & Hatai, 1899), A. agrestis (part) (Goto & Hatai, 1898), A. carnosus (Goto & Hatai, 1899), A. communissimus (Goto & Hatai, 1899), A. hilgendorfi (part) (Michaelsen, 1892), A. kamitai (Kobayashi, 1934), A. papulosus (Rosa,1896), A. phaselus (Hatai, 1930), A. serratus (Kobayashi, 1936), A. vallis (Kobayashi, 1936), A. palgongensis Hong, 2001, A. minjae Hong, 2001, and A. jamesi Hong, 2007. Most of these lack large porophores with seminal grooves and most have small genital markings in spermathecal and/or male field segments. Amynthas communissimus has manicate caeca. Only A. vallis, A. jamesi, and A. palgongensis have seminal grooves on large porophores. Annular testes sacs are present in A. vallis and A. palgongensis, but A. vallis has very long diagonal seminal grooves extending back towards 18/19. The new species is similar to A. palgongensis, but has a different shape of the spermathecal diverticulum, a shorter diverticulum relative to the ampulla, fewer setae per segment at VII, and no setae between male pores (0 vs. 1-4). The T-shaped seminal grooves of A. palgongensis are also very distinct. Looking beyond the rather superficially-defined species groups in Sims & Easton (1972), the species is similar to A. cuneatus Hong & James, 2001, whose male field consists of male discs with short seminal grooves of the same orientation. It differs from A. cuneatus in having the transverse ridges and in not having the male discs mounted on large alate extensions of XVIII. The two species differ in number of spermathecal pores, and the thickened rugose slightly pigmented areas of VI-VIII (genital patches) are lateral in A. cuneatus, rather than ventral.

Chen (1933; 1936; 1938; 1946) reported ten species of the gracilis group in China. Amynthas hasamensis sp. n. is similar to the Chinese A. muticus ( Chen, 1938) and A. magnificus ( Chen, 1936) by having male discs, but the disc shapes and spermathecal characters are different, and there are no ridges in the discs of either Chinese species.

Figures

FIG. 1 Amynthas hasamensis sp. n. (A) Ventral view. (B) Spermathecae and diverticulum. Scale bars = 2.5 mm (A), 2 mm (B).