Metaphire giengensis, Nguyen & Lam & Nguyen, 2022

Nguyen, Tung T., Lam, Dang H. & Nguyen, Anh D., 2022, Two new earthworm species (Annelida, Oligochaeta, Megascolecidae) from the Mekong delta, Vietnam, Zootaxa 5093 (4), pp. 483-492 : 487-488

Metaphire giengensis sp. nov.

( Fig. 3 )

Material examined. Holotype: 1 mature, ( CTU-EW.017.h01), Vietnam, An Giang Province, Cho Moi District, Tan My Village (Gieng islet), mango garden (10°30’39.7N - 105°30’02.7E), 2 m a.s.l., 02 February 2010, coll. Ho Minh Thuan. Paratype s: 12 matures, ( CTU-EW.017.p02), same data as for holotype. Non-types: 31 matures, ( CTU-EW.017.03), same data as for holotype, but in mango garden (10°28’45N - 105°32’56.6E); 5 matures, ( CTU-EW.017.04) and 6 matures, ( CTU-EW.DNA.017.04) same locality as for holotype, but in banana plantation (10°27’43,2N - 105°31’47,5E), 02 November 2020, coll. Lam Hai Dang.

Etymology. named after its type locality, the “gieng” islet.

Diagnosis. Small-sized worm, length 39–67 mm, diameter 1.8–2.0 mm, segments 76–131. Prostomium epilobous. First dorsal pore in 11/12. Two pairs of spermathecal pores in ventral intersegments 5/6/7. Male pores paired in xviii; ventral distance between two male pores about 0.20–0.22X body circumference. No genital markings in the spermathecal pore region, but two pairs, bean-shaped in xviii, ventrally next to secondary male pore. Holandric. Testis sacs connected. Intestinal caeca simple. Septa 8/9 thickened, 9/10 absent.

Description. External characters. Body cylindrical, small size, length 39–67 mm, diameter 1.8–2.0 mm, segments 76–131. Body colouration uniformly light brown; clitellum dark brown. Prostomium 1/3 epilobous. First dorsal pore in 11/12. Setae perichaetine, pre-clitellar setae stouter and denser than post-clitellar ones; setal numbers: 76–83 in viii, 49–61 in xxx, 6–9 between male porophores in xviii; setal distance: aa=ab, zz>zy. Clitellum annular, within xiv–xvi, without dorsal pores; clitellar setae present only in xvi ventrally. Female pore single, in mid-ventral xiv.

Two pairs of spermathecal pores located ventrally in intersegment 5/6/7; ventral distance between pores about 0.15-0.18X body circumference. No genital markings in the spermathecal region. Male pores located inside copulatory pouches which open ventrally on the setal ring of xviii; ventral distance between two openings of copulatory pouches about 0.20-0.22X body circumference; Each copulatory pouch is a shallow depression of the body wall with a large skin on the lateral side forming the openings of the pouch. Two pairs of genital markings in xviii, located medially next to the openings of copulatory pouches.

Internal characters. Septa 5/6/7/8/9 thick, 9/10 absent, 10/11/12/13 thin. Oesophageal gizzard within viii. Intestinal origin at xvi; caeca simple, originating at xxvii and extending anteriorly to xxv. Last hearts in xiii. Pharyngeal micronephridia meroic, developed in 4/5/6/7. Typhlosole simple, lamelliform. Lymph glands present from 29/30.

Spermathecae paired in vi and vii. Ampulla oval-shaped to capsule-shaped; ducts about 1/2 ampulla, robust. Diverticula cylindrical, not coiled, somewhat slightly wavy, ca. twice as long as ampulla; seminal chamber very reduced. No accessory glands in the spermathecal region.

Holandric. Testis sacs developed, connected in x–xi. Seminal vesicles well developed in xi–xii enclosing the second pair of testis sacs laterally. Ovaries well developed xiii, on ventral posterior face of septum 12/13. Ovisac invisible. Prostate glands rudimentary lobes, paired within xvii–xx; ducts robust, enlarged basally and directly attached to the body wall. Accessory glands invisible.

DNA barcode. DNA materials were extracted from CTU-EW.DNA.017.04. Partial sequences of the mitochondrial gene cytochrome oxidase subunit I (COI) were uploaded to GenBank with the accession numbers OM234761 and OM234762 . The new species has a close COI identity of 86.56% and 85.89% with Metaphire tschiliensis ( DQ835673 ) and Metaphire posthuma ( KU565289 ), respectively.

Habitat and ecology: The species was found in the depth of 0–10cm of alluvial soils in banana and mango plantations. Feces were small, pellet-like and lying underground.

Distribution: Only known from Vietnam.

Remark: Sims & Easton (1972) arranged the species of the genus Metaphire into lots of species-groups at very detailed levels. However, Metaphire ’s species with two pairs of spermathecal pores in 5/6/7 and bithecate were not yet included in any groups, and up to now, only three species with that spermathecal configuration have been recorded: M. exilis ( Gates, 1935) , M. exiloides ( Chen, 1936) , and M. easupana ( Thai & Huynh, 1993) ( Gates 1935; Chen 1936; Thai et al. 1993).

Metaphire giengensis sp. nov. is fairly similar to M. exilis and M. exiloides in the prostomium type and the presence of septum 8/9. However, the new species is different from M. exilis in having genital markings only in xviii, connected testis sacs, oval/capsule-shaped spermathecal ampulla; while M. exilis has genital markings paired in xvii and xix, separated testis sacs, and strongly reduced ampulla ( Gates 1935).

The new species is distinguished from M. exiloides by having two pairs of genital markings in xviii, the absence of septum 9/10, spermatheal diverticula being longer than ampulla; while M. exiloides has no genital markings, presence of septum 9/10, diverticula being wavy and shorter than the ampulla ( Chen 1936).

Metaphire giengensis sp. nov. differs from M. easupana in having the spermathecal pores placed ventrally, first dorsal pore in 11/12, two pairs of genital markings in xviii, intestinal origin at xv with simple caeca; while M. easupana has spermathecal pores located more dorsally, first dorsal pore in 12/13, no genital markings, and intestine origin at xiv with manicate caeca ( Thai et al. 1993).

The presence of septum 8/9 was also recorded in M. posthuma (Vaillant, 1868) re-described by Bantaowong et al. (2011), Metaphire perelae ( Thai, 1982) , M. truongsonensis (Thai, 1984) , and M. songbeensis Nguyen, Nguyen, Lam & Nguyen, 2020 ( Thai 1982; Thai, 1984b; Nguyen et al. 2020b). The new species is clearly different from these species in having two pairs of spermathecal pores in ventrally 5/6/7 (vs. laterally 6/7/ 8 in M. perelae , ventrolaterally 5/6/7/8/ 9 in M. posthuma , and dorsally 5/6/7/8/ 9 in M. truongsonensis and M. songbeensis ), two pairs of genital markings in xviii (vs. paired but not in xviii ( M. posthuma and M. songbeensis ), absent in the male region ( M. perelae and M. truongsonensis )). In addition, the new species also differs from M. posthuma in prostomium type (epilobous vs. prolobous), M. perelae in caeca (simple vs serrated), M. songbeensis in the state of septum 9/10 (absent vs. present) ( Table 2 ).

Figures

FIGURE 3. Metaphire giengensis sp. nov., Holotype (CTU-EW.017.h01). A1 & A2. Ventral view of the male region. B. Dorsal view of testis sacs and seminal vesicles. C1 & C2. Right spermatheca. D. Ventral view of the spermathecal region. E1 & E2. Intestinal caecum; F1 & F2. Right prostate gland. G. Male pore region transverse body section (Non-type: CTU- EW.017.03). H. Body wall transverse section. Scale bar = 1 mm.