Amynthas namphouinensis, Hong, Yong, 2008

Hong, Yong, 2008, Two new bithecal earthworms of the genus Amynthas (Oligochaeta: Megascolecidae) from Laos, Zootaxa 1914, pp. 57-61 : 58

Amynthas namphouinensis sp. nov.

( Fig. 1 A–B)

Material. Holotype: clitellate ( BDNUL 0001): Laos, Xayabouli Province, Nam Phouin NBCA, Phou vang Phan (18o 29.878’N, 101o 28.870’E), 495 m, 5 km from village in old forest, black soil with sand, in soil and litter layers, 30 August 2005, K. Inkhavilay coll. 4 paratypes: 2 clitellates ( BDNUL 0 0 0 3, 0004) and 2 clitellates ( NIBR), same data as for holotype. Other material: 2 clitellates, same data as for holotype.

Etymology. The species is named for its type locality.

Diagnosis. Spermathecal pores paired in 7/8 at 5th seta lines; male pores superficial in XVIII at 4th seta lines on small round porophores, 0.10–0.14 circumference apart ventrally; genital papillae equatorial in XVII, presetal widely paired in XIX; mid-ventral in 17/18; presetal, closely paired in mid-ventral in XIX; holandric, first dorsal pore in 5/6.

Description. Dimensions 63–92 mm by 3.5–4.0 mm at segment X, 4.0– 4.1 mm at segment XXX, 3.0– 3.5 mm at clitellum; body cylindrical, segments 92–94. Setae regularly distributed around segmental equators, numbering 52–61 at VII, 53–58 at XX, 0–7 between male pores, setal formula AA:AB:ZZ:YZ= 1:1:5:3 at XIII. Female pore single in XIV, on an oval area 0.2–0.3 mm in width. Prostomium epilobic with tongue open, clitellum coffee color, dorsal brown pigment fading posteriorly, formalin preservation. First dorsal pore at 4/5, 5/6, or 6/7. Clitellum annular XIV–XVI; setae invisible externally.

Male pores superficial on small round porophores in XVIII at 4th seta lines, 0.10–0.14 circumference apart ventrally; distance between male pores 1.4–1.5 mm; porophores at medial edges of reniform dark genital papillae; small grooves around male pores and longitudinal grooves between male pores. Locations of genital papillae irregular, but always paired, equatorial in XVII, and in some of the following positions: presetal, widely paired in XIX; mid-ventral in 17/18; presetal, closely paired in mid-ventral in XIX; in total usually 5– 7 papillae. Spermathecal pores paired in 7/8 at 5th seta lines, conspicuous in intersegmental furrow, 0.15–0.28 circumference apart ventrally; distance between spermathecal pores 1.4–2.0 mm. Genital markings absent.

Septa 5/6–7/8 thin, 8/9, 9/10 absent, 10/11–13/14 thin. Gizzard large between VIII–X. Intestinal origin in XV, lymph glands not found. Typhlosole small from XXVII. Intestinal caeca originating in XXVII, extending anteriorly about to XXIV, simple finger-shaped. Hearts esophageal in X–XIII. Holandric; testes and funnels in ventrally joined sacs in X–XI. Seminal vesicles paired in XI–XII with round dorsal lobe in anterior dorsal notch. Prostates in XVIII; extending between XVII–XIX; glands consisting of 2 main lobes, each divided again into 2–3 small lobes; prostatic ducts slender, muscular. Genital marking glands sessile on body wall within XVII–XIX.

Ovaries in XIII. Spermathecae one pair in VIII; ampulla thumb-shaped, stout ducts shorter than ampulla, diverticulum chamber spherical, iridescent, with slender stalk shorter than ampulla, stalk attached to duct near body wall, no nephridia on ducts. Genital marking glands not found.

Remarks. Amynthas namphouinensis sp. nov. belongs to the zebrus group ( Sims and Easton 1972). The other Laotian species of the zebrus group is A. xuongmontis ( Thai and Samphon, 1990) from Luangprabang. Among the zebrus group, A. hilgendorfi , A. palmosus , A. eleganis and A. magnipapillatus have manicate intestinal caeca. A. heaneyi from Kitanglad, Mindanao Island, Philippines is easily distinguished from the other members of the group because it is proandric ( James 2004). A. fasciculus from Guizhou, China has coiled and kinked spermathecae, whereas A. namphouinensis has a straight simple diverticulum. First dorsal pore location is unusually far forward (5/6) in A. namphouinensis , distinguishable from other species of the group. Two species from Sulawesi, A. culminis and A. zebrus , have male fields and spermathecal anatomy different from A. namphouinensis . Amynthas principalis , a large (300 mm) species from Bali, has secondary male pores with a very small penis inside each pore, which makes it unique among the zebrus group.

Amynthas namphouinensis sp. nov. shares some characteristics of the size (90 mm x 3.5 mm), first dorsal pore (5/6), segments (74), and setae (48 on VIII, 55 on XIX) with A. xuongmontis . It has no genital markings near the spermathecal pores and thus, differs from A. namphouinensis which has genital markings just front of 7/ 8 in VII. It seems unlikely that this difference is due to individual variation when all 7 specimens examined lacked genital markings in the spermathecal segments, and all of the specimens examined by Thai and Samphon (1990) had them. Amynthas namphouinensis sp. nov. has four positions of genital papillae in XVII, XVIII, and XIX: equatorial in XVII, widely paired in XIX, mid-ventral in 17/18, and closely paired in midventral XIX. In contrast, A. xuongmontis only has genital papillae only in XVIII: two pairs medial to the male porophores, and 2–5 presetal on XVIII. Also, A. namphouinensis has 0–7 setae between the male pores, but A. xuongmontis has more than 15.

Figures

FIGURE 1. Amynthas namphouinensis sp. nov. A: ventral view; B: spermathecae. Scale bars = 2.5 mm (A), 1 mm (B).