Amynthas arx, Blakemore, 2013

Blakemore, Robert J., 2013, Jeju-do earthworms (Oligochaeta: Megadrilacea) - Quelpart Island revisited, Journal of Species Research 2 (1), pp. 15-54 : 22-24

Amynthas arx sp. nov.

[Fig. 5]

Material examined. IV0000246444 holotype (H) submature specimen, sketched and dissected providing DNA sample (WM11 resampled as w4), collected from side of Haenyeos’ beach at base of Seongsan Ilchulbong or “Sunrise Peak”, Jeju 15 th Feb., 2012 by RJB .

Etymology. Latin noun ‘arx’ for ‘citadel or fortress’ after the location’s colloquial name of ‘The Floating Fortress’.

Description. Length 92 mm, segments 102. Colour in life a deep red-brown, more a chocolate-like colour in alcohol with a paler ventrum and darker mid-dorsal line. Prostomium epilobous. First dorsal pore in 12/13. Setae ca. 60- 70 per segment. Clitellum slightly darker in 14-16. Spermathecal pores lateral in 6/7/8/9lhs and 5/6/7/8/9rhs. Female pore obscure. Male pores widely paired superficial on raised white pads but within curved, longitudinal slits on 18 in shape of deeply incised “(“and”)” braces, with 35 much crowded small penial setae intervening, most concentrated nearer to the slits. Genital markings

0.02

5 10 15 20 27 1 mm

Fig. 5 with [boxed] enlargement of spermatheca in 9 and of male pore 18lhs].

February 2013 BLAKEMORE-JEJU-DO EARTHWORMS 23

not found although glands present internally in 9rhs and 9lhs.

Internally, the pharyngeal mass fills segment 4. Septa 5/6/7/8 weak, 8/9/10 absent around muscular gizzard, 10 /11-13/14 slightly thicker. Dorsal blood vessel single, hearts in 10-13. Spermathecae in 6-9lhs & 7-9rhs, small with thick muscular duct and roundish ampulla with curv- ed diverticulum (non iridescent). Glands occur near spermathecae in 9. Holandric but testis small and non iridescent; seminal vesicles anteriorly in 11 & 12. Prostates racemose, heavily parasitized in 18. Ovaries flat in 13 with no ovisacs seen in 14. Oesophagus dilated in 11-13, intestinal origin in 15. Intestinal caeca from 27, hemi-pinnate ventrally. Low but wide typhlosole from ca. 25. Gut contains soil and grits. Gregarine parasites around prostates as noted but no other parasites found.

Remarks. Specimen distinct with its red colouration, but possibly not fully mature. Its C-shaped seminal grooves, crowded setae and incised caeca appear unique. The male pores are construed as superficial rather than eversible as in Metaphire spp. and, assuming spermathecae in 5/6/7/8/9, the species would comply with an Amynthas corticis species-group of Sims & Easton (1972). Possibly a ‘species-in-transition’, losing its anterior spermathecae and approaching Metaphire with quasi-non-superficial male pores. By extension, in Metaphire it would comply with an M. ignobilis species-group and the taxon it would resembles most on Jeju probably being Metaphire quelparta ( Kobayashi, 1937) from which it differs principally in the visibility of primary male pores, the incipient retention of spermatheca in 6lhs, colouration plus other lesser characters. The penial setae, uniquely characteristic, possibly provide traction during copulation and compensate for lack of genital markings. DNA data (w 4 in Appendix) confirm its identity and shows closest match with A. aucklandis (w21). However, such DNA data cannot be used to determine whether it is correctly placed in Amynthas , the default genus for pheretimoids (see Blakemore, 2012e).