Metaphire setosa Nguyen & Nguyen & Lam & Nguyen 2020, new species

Metaphire setosa, new species

(Figs. 1, 6)

Material examined. Holotype: 1 mature (CTU-EW.179. h01), bushes (11°34′2.2″N, 106°35′46.9″E), 84.9 m, Tan Khai commune, Hon Quan District, Binh Phuoc Province, 26 October 2017, coll. Luong Thi Huynh Tien. Paratypes: 6 matures (CTU-EW.179.p02), same data as holotype.

Diagnosis. Small-sized worm, length 57.0– 73.5 mm, average diameter 1.6–3.2 mm. Prostomium not developed. First dorsal pore in 13/14. Three pairs of spermathecal pores in ventral 6/7/8/9. Setae unusual, arranged as two setal rings. Clitellum saddle-shaped, xiv–xvi. Male pores deeply located inside copulatory pouches in the setal ring xix. Five pairs of genital markings in xvi–xviii and xxi–xxii. Holandric. Intestinal caeca simple. Septum 8/9 thick, 9/10 absent.

Description. Body cylindrical, small size, length 57.0– 73.5 mm, average diameter 1.6–3.2 mm, weight 0.5–1.6 g, segments 94–121. Body pale. Prostomium not developed. First dorsal pore in 13/14. Setae unusual, arranged as two setal rings, more obvious on ventral side; pre-clitellar setae stouter and denser than post-clitellar ones; setal number 119–135 in viii, 27–42 in xxx; setal distance aa=ab, zz=zy. Clitellum saddle-shaped, xiv–xvi without setae and dorsal pores. Female pore single, on round disc-shaped pad in midventral xiv.

Three pairs of spermathecal pores in dorsal intersegments 6/7/8/9; two bean-shaped pads surrounding each spermathecal pore. No genital markings in the spermathecal region. Male pores located deeply inside copulatory pouches in the setal ring xix. Ventral distance between two openings of copulatory pouches about 0.35× body circumference. Genital markings paired ventrally in xvi–xviii and xx–xxi, one pair in each segment.

Septa 6/7/8/9 thick, 9/10 absent, 10/11/12/13 thin. Oesophageal gizzard after viii. Intestinal origin at xv; caeca simple, paired in xxvii–xxv. Last hearts in xiii. Pharyngeal micronephridia developed in 5/6/7. Typhlosole simple, lamelliform. Lymph glands absent.

Three pairs of spermathecae in vii–ix. Ampulla large, mushroom-shaped; ducts long, about ½ ampulla length. Diverticula longer than ampulla, folded and directly attached to the base of ampulla duct; seminal chamber long, bulletshaped. Spermathecal ducts without nephridia. No accessory glands.

Holandric. Testis sacs in x and xi, connected. Seminal vesicles developed in xi and xii. Ovaries in 12/13. Ovisacs invisible. Prostate glands deeply lobuled, paired in xviii–xx; duct long, folded before entering copulatory pouch which is slightly elevated from body wall. Five pairs of accessory glands.

DNA barcode. The amplification of the mitochondrial gene cytochrome oxidase subunit I (COI) failed.

Etymology. The specific epithet “ setosa ” alludes to the unusual setal arrangement on this earthworm. It is used as an adjective.

Remarks. The new species is very unique among known Metaphire species, with regard to its saddle-shaped clitellum and setal arrangement. There has been no report on Metaphire species with saddle-shaped clitellum. More interestingly, the setal pattern is completely different from all known pheretimoid species in Vietnam. The unusual setal pattern was only seen in the Amynthas polyperichaeta (Thai, 1984). The male region was finely coarse with dense setae which was known as the setal zone.