Amynthas gageodo Blakemore, 2012

Blakemore, Robert J., Park, Tae Seo & Seo, Hong-Yul, 2012, A new Korean earthworm (Oligochaeta: Megadrilacea: Megascolecidae) *, Zootaxa 3368 (1), pp. 256-262 : 256-258

Amynthas gageodo Blakemore , sp. nov.

Diagnosis: Size 150–170 mm. Spermathecal pores lateral in 5/6/7/8/9. Dorsal pores from 12/13. Genital markings as closely paired, mid-ventral, presetal discs in 8–10, 11 and in 17, 18–20 plus more widely paired postsetal discs in 8–9 and 18–19, 20 (total numbering up to twenty six with some markings unpaired unilateral, or all more widely paired). Intestinal caeca simple from 27.

Distribution: South Korea, Gageo-do Island, on slopes of Mt Doksil (34° 4' 32.73 N, 125° 6' 31.88 E; summit 639m).

Material inspected: Holotype (H), NIBR IV0000245037 , mature specimen fixed in formalin and stored in 70% ethanol (EtOH), here dissected and figured ( Fig. 1 ), collected 27.VII.2011 by Dr H.-Y. Seo and T. S. Park ; Paratype (P1), IV0000245038, undissected mature, highly contracted after fixation in 100% EtOH, with a small tissue sample taken for DNA amplification and COI barcoding analysis, collection details as for H; P2, IV0000245039, ditto P1; P3, IV0000245040, ditto P1; P4, IV0000245041, undissected mature specimen with irregular annuli in segments 19 and 20, in same batch as holotype (H); P5–P11, IV0000245042, seven mature specimens fixed in formalin in a separate jar with same collection information except that collection date was 26.IX.2011 .

Etymology: Noun in apposition after the Island’s current name (previously Gaga-do meaning “Beautiful Island” also called Soheuksan-do or Little Heuksan Island from the Japanese colonial period; since 1896 it is known as Gageo-do or “Liveable Island”).

Description: Body length 155 mm (holotype H), ca. 150–170 mm paratypes, segments 91 (H). In life, a dark greyish-brown; preserved, dorsum dark grey to ca. 23 then brown with lighter grey clitellum and paler ventrum. First dorsal pore 12/13. Setae 66–74 per segment behind segment 12 (H, P1). Spermathecal pores ca. 0.3 circumference apart in 5/6/7/8/9. Genital markings closely paired mid-ventral and presetal disks in 8–9,10,11 and in 17,18–19,20 plus more widely paired and postsetal in 8–9 and 18–19,20; thus usually eight or more in both spermathecal and male fields, with some markings unpaired, unilateral; occasionally all presetal markings in 8–10 paired as widely as the postsetal ones in 8–9 e.g. in P2 and one of paratypes P5–11. Maximum markings per worm were twenty-four in one of the latter paratypes (150 mm long posterior-amputee) that had two unilateral markings (in 8 and 20), thus indicating potentially thirteen pairs or twenty-six markings in total.

Internally, small sessile glands correspond to the external genital markings. Other accessory glands found neither in spermathecal nor male fields. The pharyngeal mass extends to 4 and tufted meroic nephridia are in forests on anterior of 5/6 and 6/7. Septa none especially thickened, 8/9/10 are aborted; 10/11/12/13 are slightly stronger, thereafter membranous. Spermathecae in 6–9 with slender, clavate diverticula (terminal bulbs inseminated) each about half the length of the duct plus saccular ampulla combined. Dorsal vessel single; hearts in 10–13. Testis in small sacs, paired anteriorly in 10 and 11; seminal vesicles moderately large in 11 and 12; pseudovesicles on posterior of 12/13 and 13/14 (the latter possibly vestigial ovisacs). Ovaries and funnels in 13. Intestine origin in 16 with simple caeca from 27 extending forward to 24; typhlosole not found. Gut contains organic debris suggesting a detritivorous diet.

Remarks: The current species appears particularly close to A. carnosus ( Goto & Hatai, 1899) from Japan, Korea and probably China which is itself comparable to Chinese A. pingi ( Stephenson, 1925) that is provisionally maintained separately as per Blakemore (2002, 2003a, 2003b, 2008, 2010b, 2012). Kobayashi (1936a) studied two Japanese specimens of A. carnosus (sent with tacit agreement of S. Hatai, the original author) plus 204 Korean specimens having variations of up to eight markings in some of 7,8–9 and six or fewer in 18–19. Kobayashi (1936a) also placed his Pheretima kyamikia Kobayashi, 1934 in synonymy as soon as this became apparent – as any good scientist would – and he considered the genital marking variations he encountered encompassed those in A. pingi . Indeed, Chen (1933: 231) had allowed papillae as rarely absent or one to three pairs (occasionally up to five pairs in total) near male and spermathecal pores in his concept of A. pingi , while having fourteen or fewer markings seems permissible for A. carnosus proper ( Blakemore 2012). In contrast, A. gageodo markings may total up to twenty-six, with eight to twelve preclitellar markings and a similar number and arrangement in the corresponding postclitellar male pore region. On this feature alone, it is considered a species new to science with unambiguous objective confirmation provided via DNA COI barcoding of its types (Appendix).

Habitat and Species Associations: Humid litter layer of dense silver magnolia (Magnolia sp.) and sloumi ( Daphniphyllum macropodum ) evergreen forest. Terrestrial leeches were identified as Orobdella sp. while unidentified earthworm-feeding Bipalium sp. planaria were also present (specimens in NIBR). Lizards were common on site and the island has an abundant avifauna ( Anonymous 2010), both groups likely predators. An Eisenia sp. lumbricid, possibly an introduced species that is to be described elsewhere, was found sympatrically on the island.

Behaviour: Rapid ‘snaking’ escape movement when its litter habitat is disturbed. Evidence from a later NIBR survey in 2012 indicates that this worm enters some form of diapause during the coldest winter period.

Figures

FIGURE 1. Amynthas gageodo sp. nov., holotype showing prostomium, ventral view of body with spermathecae and prostates in situ (genital markings nearby), posterior pygidium, and intestinal caecum in 27; plus an enlargement of 6lhs (left-hand-side) spermatheca.