Amynthas nhonmontis, Nguyen, Anh D. & Nguyen, Tung T., 2015

Nguyen, Anh D. & Nguyen, Tung T., 2015, Notes on Metaphiremultitheca (Chen, 1938) (Oligochaeta, Megascolecidae) recorded from Vietnam, with descriptions of two new species, ZooKeys 506, pp. 127-136 : 129-132

Taxon classification Animalia Opisthopora Megascolecidae

Amynthas nhonmontis sp. n. Fig. 2

Material examined.

Holotype. 1C (CTU.EW 023-h01) natural forest, Nhon mountain, (104°56'09.2"E, 10°35'39.6"N), elevation of 56 m a.s.l., Tinh Bien district, An Giang province, Vietnam, 7 November 2010, coll. Nguyen Thanh Tung. Paratypes. 6C (CTU. EW023-p02) same data as for holotype.

Diagnosis.

Medium-size worm. First dorsal pore in 10/11. Prostomium prolobous. Multiple spermathecal pores ventral in intersegments 5/6/7/8. Male pores in xviii, without copulatory pouches. Three pairs of genital markings present in xvii, xix and xx, rarely more or less than three pairs. Holandric. Intestinal caeca simple, from xxvii. Septa 8/9/10 absent, 10/11 thickened.

Etymology.

“nhonmontis”, after locality.

Description.

External characters: Body cylindrical, medium size. Length 103-106 mm, diameter 3.28-4.05 mm, segments 138-168, weight 0.91-1.65 g. Living specimens whitish pink while preserved specimens uniformly whitish brown; clitellum darkish brown.

Prostomium prolobous. First dorsal pore in 10/11. Setae perichaetine; preclitellar setae stouter and thicker than postclitellar setae, 42-51 in viii, 31-36 in xxx, 5-8 between male porophores in xviii; setal distance aa=ab, zz=zy. Clitellum annular, xiv–xvi, without setae and dorsal pores. Female pore single, mid-ventral in xiv. Body wall thinned, especially segments after male region having very thin wall. Preclitellar segments obviously shorter than postclitellar ones.

Multiple spermathecal pores ventral in intersegments 5/6/7/8. No genital markings in spermathecal region. Male porophores flattened; male pores located in setal ring in xviii, without copulatory pouches. Ventral distance between male porophores about 0.3x body circumference. Genital markings usually three pairs in setal rings in xvii, xix and xx, rarely more or less than three pairs; genital markings arranged in longitudinal line with male pores.

Internal characters: Septa 5/6/7/8 and 10/11 thickened, 8/9/10 absent, 11/12/13 very thin. Oesophageal gizzard within viii–x. Intestinal origin at xv; caeca small, simple within xxvii–xxvi or xxvii–½ xxv. Last hearts in xiii. Pharyngeal micronephridia well-developed on septa 4/5/6. Lymph glands lobulated from xxvii. Typhlosole simple, lamelliform.

Spermathecae small, about 43-48 altogether in intersegments 5/6/7/8: 11-13 in 5/6, 15-17 in 6/7, and 17-18 in 7/8. Spermathecal ampulla very small, clavate, yellowish brown; duct extremely short. Diverticulum shorter and attached directly to duct of ampulla. No accessory glands.

Holandric. Testis sacs separated. Seminal vesicles poorly developed in xi–xii. Oviduct on septum 12/13 ventrally. Ovaries minute (not clearly found). Prostate glands poorly developed, largely lobulated, only within xviii; prostatic ducts undetected, covered body wall. Accessory glands concealed within body walls.

DNA.

COI barcode data (partial) is for holotype uploaded to GenBank with accession number KR676559.

Habitats and ecology.

This species has been found only in Nhon mountain (Tinh Bien district) in An Giang province. Adult specimens were only collected during the rainy season (from October to March) in southern Vietnam and found in heavy clays at the foothill of Nhon mountain.

Remarks.

Amynthas nhonmontis sp. n. differs from other Amynthas species in having multiple spermathecal pores ventral in intersegments 5/6/7/8 and three pairs of genital markings in xvii, xix and xx. The new species is superficially similar to Polypheretima elongata (Perrier, 1872) due to external morphology: body cylindrical, multiple spermathecae per segment, presence and arrangement of genital markings near male pores. However, it is clearly distinguished from Polypheretima elongata by presence of intestinal caeca, three spermathecal segments, absence of copulatory pouches.

Its DNA barcode is definitive for the new species (nearest BLAST result is Amynthas morrisi at 87%).