Amynthas calculatus, Hong & James, 2009

Hong, Yong & James, Samuel W., 2009, Some new Korean Megascolecoid earthworms (Oligochaeta), Journal of Natural History 43 (21 - 22), pp. 1229-1256 : 1246-1248

Amynthas calculatus sp. nov.

( Figure 10 )

Type material

Holotype: Clitellate (NIBRIV0000120471) specimen: Korea, Chungcheongbuk-do, Boeun-gun, Mt Songni , 18–22 August 1971, J.S. Son coll.

Etymology

The name calculatus is Latin for provided with pebbles, here referring to the shape of the male pore region.

Diagnosis

Three pairs of spermathecal pores, presetal in VI–VIII just below mid-lateral, 0.30 mm circumference apart; male field composed of two 2.7–3.8-mm diameter elevated discs with complex ornamentation, 0.25 mm circumference apart.

Description

Brown dorsal pigment. Dimensions 115 by 4.6 mm at segment X, 4.2 mm at XXX, 4.5 mm at clitellum; body cylindrical throughout, segments 99. Setae regularly distributed around segmental equators, numbering 36 at VIII, 47 at XX; four between male pores; setal formula AA: AB: YZ: ZZ = 5.5: 2: 4: 4 at XIII. Female pore single in XIV, 0.7 mm, oval-shaped. First dorsal pore 12/13.

Male field composed of two 2.7–3.8-mm diameter elevated discs with complex ornamentation, 0.25 mm circumference apart. Paired epidermal thickenings centred on XVIII, extending from posterior quarter of XVII to anterior quarter of XIX, thickenings 2.7–3.8 mm long; each with transverse pebble-textured ridge equatorial on XVIII and ring-shaped grooves anterior, posterior to ridge, two pairs of rounded quadrangular papillae within the paired epidermal thickenings. Three pairs of spermathecal pores 0.2–0.3 mm conspicuous, presetal in VI–VIII just below mid-lateral, some furrowed, hardened areas on segmental equators VI–VIII, spermathecal pores 0.30 mm circumference apart.

Septa 5/6, 6/7, 7/8 thick, 8/9, 9/10 absent, 10/11–13/14 thickly muscular. Gizzard globular in VIII–X. Intestine begins XV, lymph glands small from XXVII. Typhlosole medium size fold from XXVII. Hearts X–XIII oesophageal, IX lateral, X and XI inside testes sacs. Intestinal caeca simple, originating in XXVII, and extending anteriorly to about XXVI, each consisting of a finger-shaped sac, each finger with seven or eight serriform outgrowths on ventral margin.

Ovaries in XIII. Three pairs of spermathecae VI–VIII; each ampulla medium size voluminous ovate pouch, ducts short, thin, diverticula club-shaped, longer than ducts, shorter than ampulla; no nephridia on spermathecal ducts. Male sexual system holandric, testes and funnels X, XI in ring-shaped sacs formed by dorsal and ventral fusion, enclosing other segmental contents of X, XI. Seminal vesicles in XI, XII with small dorsal appendage. Prostates XVIII, extending to XVII–XX, each divided into two or three main parts, ducts thick, short, muscular.

Remarks

Amynthas calculatus sp. nov. and the next three species, which have intrasegmental spermathecal pores on VI, VII and VIII, key out to the bournei -group in Sims and Easton (1972). The bournei -group is composed of seven species: A. bournei (Rosa, 1890) , A. sulcatus (Gates, 1932) , A. domosus ( Chen, 1946) , A. mucrorimus ( Chen, 1946) , A. koryoensis ( Kobayashi, 1936) , A. vallis ( Kobayashi, 1936) and A. pagyeiensis Hong, 2001 . Both A. domosus and A. mucrorimus , from China, have genital markings, but A. koryoensis , A. vallis , A. pagyeiensis , A. calculatus sp. nov. and the next three species of the bournei -group have no genital markings. All these Korean bournei -group species have male fields with disc-shaped porophores. The present new species differs from other bournei -group species with respect to the male disc shape, and it has conspicuous spermathecal pores, presetal in hardened areas on VI–VIII just below mid-lateral.

Figures

Figure 10. Amynthas calculatus sp. nov.: ventral view and spermathecae.