Amynthas simplex, Blakemore, 2013

Blakemore, Robert J., 2013, Jeju-do earthworms (Oligochaeta: Megadrilacea) - Quelpart Island revisited, Journal of Species Research 2 (1), pp. 15-54 : 34

Amynthas simplex sp. nov.

[ Fig. 12 ]

Material examined. IV0000251102 Holotype (H) mature specimen from Mt Halla under bridge on Rt 516, 12 th June, 1023; providing DNA sample ( WO43 resampled as w23). Paratype (P) in same jar, undissected .

Etymology. Latin for “simple” due to its lack of GMs and other complex attributes (Non Michaelsen, 1928).

Description. Length 80 mm (H), 60 mm (P). Segments 100 (H), 101 (P). Darkish dorsum but transparent ventrum when preserved with internal parasites visible, clitellum buff and rather knobbly (H & P) possibly due to parasitism. First segment reduced with thin and wide epilobous prostomium. First dorsal pore minute in 12/13, open from 13/14 (H & P). Spermathecal pores ca. 0.3 C apart in 5/ 6/7/8/9. Setae ca. 24ish per segment with ventral gaps in anterior; the penultimate three segments of ‘tail’ lack setae. No GMs. Male pores small in centres of large circular flat porophores. Nephridial forests in 5 & 6. Septum 8/9 aborted, 9/10 displaced by gizzard. Holandric with large testis sac in 10 and seminal vesicles in 11 & 12. Hearts 10-13. Ovaries in 13, no ovisacs present. Oesophagus vascularized and dilated in 12 & 13. Intestine from 15. Intestinal caeca simple. No typhlosole. Gut contains organic soil. Some large nematodes and much mucus seen in anterior segments, with many gregarine cysts, especially on ventral nerve cord under intestine.

Remarks. Similarities to A. phaselus are lack of GMs, ruggose spermathecae and simple, circular male fields. Differences are an extra pair of spermatheca in 8/9 and non-incised intestinal caecae. The other similar Jeju species with spermathecae in 5/6-8/9 and simple caeca is Amynthas sangumburi Hong & Kim, 2002 that, however, is smaller (46-68 mm), has more setae (39-43 with only 3-4 between male pores) and quite different shape of spermathecae plus a large typhlosole from 27. These specimens are named as new on the basis of these morphological differences that, unfortunately, could not yet be confirmed by DNA.

Figures

Fig. 12. Amynthas simplex sp. nov. H. Ventral view with prostomium and pygidium, spermathecae and prostates in situ; caeca 27rhs.