Polypheretima mekongmontis, Nguyen, Tung T., Tran, Binh T. T. & Nguyen, Anh D., 2014

Nguyen, Tung T., Tran, Binh T. T. & Nguyen, Anh D., 2014, Earthworms of the ' acaecate' Pheretima group in Vietnam (Oligochaeta: Megascolecidae), with description of a new species from the Mekong delta, Zootaxa 3866 (1), pp. 105-121 : 118-119

Polypheretima mekongmontis sp. nov.

( Figs 3 , 6 )

Type material. Holotype: 1C (CTU. EW028—h01) Kien Giang Province, Hon Dat District, Hon Me Mt. (10º06' 12.3N; 104º52' 43.5E), mango garden, 13 November 2010, coll. Nguyen Thanh Tung. Paratypes: 10C (CTU. EW028—p02), same data as holotype.

Further material. 3C, Kien Giang Provinve, Hon Dat District, Mt. Hon Soc (10º09' 48.1N; 104º54' 23.2E); 3C, Kien Giang Provinve, Hon Dat District, Mt. Hon Dat (10º06' 37.6N; 104º53' 06.2E), 13 November 2010, all coll. Nguyen Thanh Tung.

Diagnosis. Small to medium body size, prostomium prolobous, first dorsal pore in 12/13, polythecal, spermathecal pores in 4/5/6/7, male pores paired in XVIII, each in a copulatory pouch with a large opening, genital markings large, paired in XVII and XIX, anterior pair in XVII directing towards the mid-ventral part, clitellum annular, XIV–XVI, intestinal caeca absent, testes paired, ventral, holandric, septa 8/9/10 absent.

Etymology. Named after its location, which is the mountain region of the Mekong Delta, Vietnam.

Description. Body length 65–101 mm, diameter 1.58–3.36 mm, fresh weight 0.3–1.1 gr, segment number 122–160. Colour similar on dorsum and ventrum, brownish in front of clitellum, brown around clitellum, with a greyish black tail. Prostomium prolobous. First dorsal pore in 12/13. Setae 37–49 in VIII, 40–53 in XXX, 4–7 between male pores, aa = 1.2–1.5 ab, zz = 1.3–2 zy. Clitellum annular, XIV–XVI, smooth, setae and dorsal pores absent. Polythecal, spermathecal pores ventrolateral in 4/5/6/7, not more than 4 pairs per segment, number of spermathecal pores gradually increasing from anterior to posterior segments, distance between paired spermathecal pores about 0.3 body circumference ventrally. Female pore single, mid-ventral in XIV. Male pores paired in XVIII, ventro-lateral, distance between pores about 0.30 body circumference ventrally, each in a copulatory pouch with a large opening. Genital markings large, paired in XVII and XIX, anterior pair in XVII directing towards the midventral part.

Septa 5/6/7/8 thick, 8/9/10 absent, 10/11/12 /13 thin. Gizzard round in IX–X. Intestine enlarged from XV or XVI. Intestinal caeca absent. Last lateral hearts in XII. Pharyngeal micronephridia in 5/6/7. Lymph glands absent. Overal number of spermathecae in V–VII 13 to 18. Ampulla oval, spermathecal diverticula present, stalk coiled, shorter than ampulla, originating from spermathecal duct. Accessory glands absent in spermathecal region. Typhlosole simple, lamelliform. Holandric, testes sacs paired in X and XI, small, separated, ventral, yellowish. Seminal vesicles paired in XI and XII, divided into several small lobes. Ovaries paired in ventral XIII, ovisacs developing in XIII, less so in XIV. Prostate glands paired in XVIII, extending anteriorly to XVII and posteriorly to XIX. Prostatic duct C-shaped. Accessory glands ( Fig. 6 E) hidden under parietes.

Locality and habitat. Examined specimens were collected from sandy soil in the mango garden in Kien Giang Provinve (Hon Dat, Hon Soc and Hon Me Mountain—Hon Dat District, Den Mountain—Ha Tien Town); An Giang Province (To Mountain—Tri Ton District). All mature specimens were collected in November, 2010. A lot of their castings could be seen on the surface of the soil where they live ( Fig. 6 F).

Remarks. The new species is fairly similar to Polypheretima spiridonovi ( Thai, 1996) in the following characters: first dorsal pore in 12/13, polythecal with spermathecal pores in 4/5/6/7, last lateral hearts in XII, septa 5/ 6/7/8 thick, lymph gland absent, ovisacs in XIII. It differs from Po. spiridonovi in the following: copulatory pouches in XVIII, paired genital markings in XVII and XIX, lower number of spermathecae.

Figures

FIGURE 3. Distribution of species of the genus Polypheretima in Vietnam. The exotic Po. elongata with many records all over the country is omitted.

FIGURE 6. Polypheretima mekongmontis sp. nov., holotype (A – E, G). A. Male pore region (mp = male pore, gm = genital marking). B. Spermathecae (amp = ampulla, dv = diverticula). C. Prostate gland. D. Copulatory pouch, transverse body section E. Accessory gland, transverse body section. F. Casts. G. Ventral view of clitellum and male pore region. Scale bar = 1 mm (for A, B, C), = 10 mm (for G).