Amynthas aeruginosus Kinberg, 1867, by monotypy.

Widely distributed in the Oriental region, and also found in Australasian and Oceanian regions (Sims and Easton 1972) and distributed worldwide (Blakemore 2002, 2007).

Members of the genus can be easily recognized by the presence of intestinal caeca near xxvii, the absence of copulatory pouches, and often by absence of micronephridia on spermathecal ducts. It is noted that about 500+ nominal species have been recorded, but a considerable number are likely synonyms (Blakemore 2002, 2007).

Holotype. 1C (CTU–EW 071.02–h01) taro garden, Duc Pho commune (108°57'9"E, 14°48'18"N), elevation of 5 m a.s.l., Pho Minh district, Quang Ngai province, Vietnam, 15 April 1995, coll. Huynh Thi Kim Hoi. Paratypes. 13C (CTU–EW 071.02–p02) same data as for holotype. Further material. 8C (SORC–V.153.01) garden, Duc Pho town, Pho Minh, Quang Ngai, 15 April 1995, coll. Huynh Thi Kim Hoi. Fixed in formalin.

Medium-size worm. First dorsal pore in 11/12 or 12/13. Prostomium 1/3 epilobous. Multiple spermathecal pores lateroventral in intersegments 5/6/7/8/9. Male pores located in xviii, without copulatory pouches. Two pairs of crescentic genital markings in xviii. Holandric. Testis sacs not separated. Intestinal caeca simple, within xxvii-xxv. Septa 8/9/10 absent.

To emphasize the misidentification of the species as Pheretima multitheca.

External characters: Body cylindrical, medium size. Length 112–150 mm, diameter 3.81–5.0 mm, segments 119–150, weight 1.61–2.94 g. Body coloration uniformly brown. Setae perichaetine, more concentrated ventrally; preclitellar setae sparser than postclitellar setae, 42–46 in v, 37–65 in viii, 61–71 in xxv, 42–72 in xxx, 10–16 between male porophores in xviii; setal distance aa=2ab, zz=1.5zy. First dorsal pore in 12/13, rarely in 11/12. Prostomium ⅓ epilobous. Clitellum annular, xiv-¾xvi, darkish brown, smooth and without setae and dorsal pores. Female pore single, mid-ventral in xiv.

Spermathecal pores round and small, multiple, lateroventral in intersegments 5/6/7/8/9, sometimes invisible. No genital markings in spermathecal region.

Male pores located in porophores in xviii, without copulatory pouches; ventral distance between male porophores about 0.28× body circumference. Two pairs of large, crescentic genital markings in xviii, located in front of and behind male porophores.

Internal characters: Septa 6/7/8 thickened, 8/9/10 absent, and 10/11/12/13 relatively thickened. Oesophageal gizzard after 7/8, pear-shaped. Intestinal origin at xv; caeca simple, within xxvii–xxv. Last hearts in xiii. Pharyngeal micronephridia developed in 4/5/6. Lymph glands present from xvii, rarely xvi, and lobulated. Typhlosole simple, lamelliform.

Spemathecae variable, 21–27 altogether in 5/6/7/8/9: 2–4 in 5/6, 4–6 in 6/7, 5–7 in 7/8 and 6–8 in 8/9. Spermathecal ampulla large, oval; duct about ⅓, rarely as much as ½ the length of the ampulla. Diverticula irregularly sinusoidal, folded onto itself several times, enlarged distally, about half length of ampulla; stalk attached to base of duct of ampulla. No accessory glands.

Holandric. Testis sacs not separated, developed in x and xi. Seminal vesicles well developed within xi–xii, yellowish white. Oviduct poorly developed on septum 12/13 posteriorly; a pair of ovaries in xiii. Prostate glands racemose, paired in xvii–xix; prostatic ducts C-shaped. Two accessory glands present.

COI barcode data not yet available.

The species was found in soils in which old growth trees had been grown. No other ecological data had been recorded.

Previous misidentifications of Pheretima multitheca multitheca were from Quang Tri (Quang Tri town); Thua Thien Hue (Huong Tra; Hue; Nam Dong; Phu Loc); Danang; Quang Nam (Que Son); Quang Ngai (Quang Ngai city; Duc Pho); Binh Dinh; Dak Nong (Ta Dung Mts.) (Nguyen 1994, Pham 1995, 2010, Huynh 2005a, 2005b, Nguyen and Tran 2008).

This new species was previously misidentified as Pheretima multitheca multitheca Chen, 1938 (= Metaphire multitheca), which was originally known only from Hainan Island. Both species share multiple spermathecal pores per segment and presence of intestinal caeca. However, Amynthas erroneous sp. n. has multiple spermathecal pores in intersegments 5/6/7/8/9, and lacks copulatory pouches while Metaphire multitheca (Chen, 1938) has multiple spermathecal pores located behind setal rings of segments vi, vii, viii, and presence of copulatory pouches. The new species is also fairly similar to Metaphire multitheca dipapillata (Thai & Tran, 1986), now M. dipapillata stat. n.; both species have multiple spermathecal pores in intersegments 5/6/7/8/9, and genital markings associated with the male pores. However, Amynthas erroneous sp. n. lacks copulatory pouches and has two pairs of crescentic genital markings in xviii, whereas Metaphire dipapillata has copulatory pouches and only a pair of genital markings in 17/18, located in front of male porophores. Marker characters of three species, A. erroneous, M. dipapillata and M. multitheca are presented in Table 1.

The new species is also distinguished from other 5/6/7/8/9 polythecate species such as Polypheretima bifaria (Michaelsen, 1924) from New Guinea, Po. polytheca (Beddard, 1900b) from Malay penisula, Po. koyana Michaelsen, 1934 from Sarawak, and Metapheretima elrondi Easton, 1979 from New Guinea by having intestinal caeca. Althought it shares with Amynthas bleckwenni (Ude, 1925) from Borneo the multiple spermathecae at 5/6/7/8/9, and having intestinal caeca, the new species differs from A. bleckwenni in having two pairs of crescentic genital markings in front of and behind male pores on xviii.

We herein raised the subspecies M. multitheca dipapillata to full rank as M. dipapillata stat. n., and also restore M. multitheca multitheca as M. multitheca.

The new species is widely distributed in central parts and highlands of Vietnam. Surprisingly, it has never yet been found in northern and southern Vietnam.

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.

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.

“nhonmontis”, after locality.

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–½xxv. 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.

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

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.

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 Po. 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%).