Metaphire dorsomultitheca Nguyen & Nguyen, 2015

Nguyen, Tung. T., Trinh, Binh K. T., Le, Nhan V. & Nguyen, Anh D., 2015, On the polythecate earthworms of the genus Metaphire (Oligochaeta: Megascolecidae) from Vietnam, with descriptions of three new species, Raffles Bulletin of Zoology 63, pp. 461-470 : 465-467

Metaphire dorsomultitheca Nguyen & Nguyen , new species

( Fig. 2 , Tables 2, 3)

Examined material. Holotype: 1C (CTU.EW025–h01) natural forest, Sam Mountain (10°40’06.8 N; 105°04’50.2 E), Chau Doc District, An Giang Province, Vietnam, 06 November 2010, coll. Nguyen Thanh Tung. Paratypes: 8C (CTU.EW025–p02) same data as for holotype.

Further material. 3C (CTU.EW025–p03) natural forest, To Mountain (10°23’09.2 N; 105°00’22.8 E), Tri Ton District, An Giang Province, Vietnam, 09 November 2010, coll. Nguyen Thanh Tung.

Diagnosis. Body small, length 76–111 mm, diameter 2.9–3.6 mm. Setae perichaetine; pre-clitellar setae sparser than postclitellar setae; setae distance aa = 1.3–2.0 ab, zz = 1.2–1.6 zy. First dorsal pore in 12/13. Multiple spermathecal pores dorsal in intersegments 7/8/9. Two pairs of genital markings present, but hiding inside copulatory pouches. Holandric. Intestinal caeca simple. Septa 8/9/10 absent.

Etymology. “ dorsomultitheca ” a noun in apposition to emphasize multiple spermathecal pores on dorsum.

Description. External characters: Body cylindrical, small size; length 76–111 mm, diameter 2.9–3.6 mm, segments 88–120, weight 0.43–0.54 g. Body uniformly greyish brown except clitellum darkish brown. Setae perichaetine; pre-clitellar setae sparser than post-clitellar setae, 29–32 in v, 33–40 in viii, 45–51 in xxv, 39–50 in xxx, 6–8 between male porophores in xviii; setal distance aa = 1.3–2.0 ab, zz = 1.2–1.6 zy. Prostomium 2/3 epilobous. First dorsal pore in 12/13. Clitellum annular, xiv–xvi, smooth and without setae and dorsal pores. Female pore single, mid-ventral in xiv.

Spermathecal pores tiny, multiple, dorsal in intersegments 7/8/9. No genital markings in spermathecal region.

Male pores deeply located inside copulatory pouches in xviii; ventral distance between male porophores about 0.3× body circumference. Two pairs of genital markings present, but invisible due to hiding inside copulatory pouches.

Internal characters: Septa 6/7/8 thickened, 8/9/10 absent, and 10/11/12/13 thin. Oesophageal gizzard within viii–x. Intestinal origin at xv; caeca simple, within xxvii–xxiv. Last hearts in xiii. Pharyngeal micronephridia in 4/5/6, but well developed in 5/6. Lymph glands present from xv. Typhlosole simple, lamelliform.

Spemathecae variable, about 41–65 altogether in intrasegmental 7/8/9: 19–31 in 7/8 and 24–37 in 8/9 ( Table 2). Spermathecal ampulla cylindrical, but enlarged distally. Diverticula waved, shorter than ampulla; distal part with an opalescent, oval-shaped chamber; duct attached to base of ampulla. No accessory glands.

Holandric. Testis sacs not separated. Seminal vesicles well developed within xi–xii. Oviduct on septum 12/13 posteriorly; ovaries not visible. Prostate glands racemose, paired in xvii–xx; prostatic ducts U-shaped, slightly getting smaller distally, opening into large chambers. Two accessory glands present, highly elevated towards body coelom, and being covered with thick muscle layer.

Habitat and ecology. A total of nine specimens was collected in a mountainous area of the Cuu Long River Delta: Sam mountain and To mountain in An Giang Province. The species was found in sandy soils or light-clay soils with small rocks in environs of low humidity .

Like Metaphire kiengiangensis , adult specimens of this new species were only collected in November in rainy season.

Remarks. The new species shares with Metaphire kiengiangensis , new species, M. multitheca ( Chen, 1938) , and M. bitheca ( Kobayashi, 1936) by having multiple spermathecae. It differs clearly from all three species in dorsally located spermathecal pores whereas the other three species have ventral or lateroventral spermathecal pores ( Table 3). The new species is distinguished from M. kiengiangensis by genital markings hiding inside copulatory pouches in male region, two thecal segments; ampulla without ducts; septa 11/12/13 thin. M. multitheca ( Chen, 1938) differs from new species in having two pairs of genital markings in front of and behind male porophores in xviii, multiple spermathecal pores on posterior border of segments vi, vii and viii. M. bitheca ( Kobayashi, 1936) is distinguished from new species by absence of genital markings in both spermathecal and male regions, two grouped pairs of spermathecal pores on anterior vi and vii with each group consisting of 2+2 pores, large, oval, disc-shaped male porophores, and short, cylindrical spermathecal diverticula.

Figures

Fig. 2. Metaphire dorsomultitheca, new species, holotype. A, spermathecal region (sp = spermathecal pores); B, spermathecae, left side (am = ampulla; dv = diverticula); C, male pore region (mp = male pore); D, Prostate gland (ag = accessory gland); E, intestinal caeca; F, G, transverse body section of segment xviii: F, accessory glands; and G, male pore. Scale bars = 1mm.