Metaphire taiwanensis, Tsai & Tsai & Shen, 2004

Tsai, Chu-Fa, Tsai, Su-Chen & Shen, Huei-Ping, 2004, A new gigantic earthworm of the genus Metaphire Sims and Easton (Megascolecidae: Oligochaeta) from Taiwan with reference to evolutional trends in body sizes and segment numbers of the Pheretima genus-group, Journal of Natural History 38 (7), pp. 877-887 : 878-881

Metaphire taiwanensis sp. nov.

(figure 1)

Type material

H  : a mature (clitellate) specimen (dissected) collected 29 May 1999 from Mt Beidongyan (elevation 1800 m) west of the Central Mountain Range , Nantou Co. by C . T. Yao (coll. no. 1999-9) .

Other material

One mature specimen (dissected) collected July 1994 from the same locality as the holotype by C. T. Yao (coll. no. 1999-23-Shen); one immature (aclitellate) specimen (dissected) collected on 19 October 1999 from Meifeng (elevation 2100 m), Nantou Co. by C. F. Tsai, S. C. Tsai and H. P. Shen (coll. no. 1999-16-Shen) .

External characters

Large earthworms, length (mature) 637–655 mm, clitellum width 16.1–17.2 mm, weight 101–121 g. Prostomium prolobous. Number of segments 185–228. Number of annuli (secondary segmentation) per segment three in V –XIII and on the ventrolateral portion of some body segments. Setae short, numerous, 167–188 in VII, 135–145 in XX, 24 between male pores. First dorsal pore in 12/13 or 13/14. Clitellum XIV–XVI, smooth, setae absent, length 16.45–19.85 mm. Spermathecal pores four pairs in 5/6–8/9, minute, inside segmental furrows, invisible externally. Female pore single in medio-ventral in XIV, large, swollen, pale in colour (figure 1A).

Male pores (opening of copulatory pouches) small, paired, ventro-lateral in XVIII, the distance between the pores 0.27–0.29 circumference apart, slightly elevated (figure 1A). Each pore L-shaped, bordered laterally and posteriorly by a thick skin-cover with folds, medially by porophore, and anteriorly by a genital pad. Porophore circular in shape, top flat, tuberculated densely in holotype, and with five small tubercles in the other clitellate specimen. Male aperture inconspicuous. Genital pad flat, oval in shape, as large as or larger than porophore. Porophore and genital pad surrounded by circular folds, which extend anteriorly to 17/18 and posteriorly to 18/19 (figure 1A, B). The male pore region swollen, pale in colour.

Preserved specimens bluish brown around the head (preclitellar) region. Clitellum dark bluish brown on dorsum, greyish brown on ventrum, and its segmental borders (furrows) pale grey lines, as if the clitellum is divided into three segments. Body bluish brown on dorsum, light greyish brown on ventrum.

Internal characters

Septa 8/9/10 absent, 7/8 and 10/11–12/13 thickened. Gizzard round in IX and X. Intestine enlarged from XV. Intestinal caeca paired in XXVII, simple, long, surface slightly wrinkled (figure 1F), extending anteriorly to XIX in holotype, but to XXI in aclitellate. Oesophageal hearts enlarged in X–XIII.

Spermathecae four pairs in VI –IX. Ampulla oval or heart-shaped, 9.0 mm in length, 3.2 mm in width, with a short stalk of about 1.2 mm long. Diverticulum small, with an oval, smooth, white seminal chamber 1.6 mm in length and a short coiled or twisted stalk (figure 1C). Nephridia tufted, around the wall of the alimentary canal in segment chambers of the head region anterior to 6/7 septum. Ovaries paired in XIII, folliculated, attached in medio-ventral position posterior to 12/13 septum, funnel-shaped oviduct opening in medio-ventral position anterior to 13/14.

Protandry: testis sacs paired in X, smooth, oval, white in colour, medio-ventral in front of 10/11. Seminal vesicles paired in XI, large, occupied entire segmental space, surface slightly tuberculated, yellowish in colour, each with a large, white dorsal lobe (figure 1D). Seminal vesicles in XII, vestigial, yellowish, surface tuberculated (figure 1D). Prostate glands paired in XVIII, large, oval, yellowish brown, lobulated, extending anteriorly to the posterior portion of XVII and posteriorly to the anterior portion of XIX. Prostate duct short, stout, slightly curved (figure 1E).

Habitat

Mt Beidongyan at elevation of 1800 m is covered with natural broadleaf forests. The holotype (1999-9) and the other clitellate (1999-23-Shen) were picked up on a narrow, paved mountain road after rain by Mr C. T. Yao, an ornithologist who had made a routine bird survey in the area. On the same road we also collected two aclitellates of about 50-cm long in mud piles a few inches below the surface. They escaped after being brought to the laboratory. The other aclitellate (1999-16-Shen) was collected underneath a large flowerpot at the foot of the mountain slope at the High-altitude Horticulture Experimental Station of National Taiwan University, Meifeng at an elevation of 2100 m. The mountain slope was covered with natural broadleaf forests. We also conducted an earthworm survey along the road in the Rueyen Nature Reserve at an elevation of 2300 m north-east to Mt Beidongyan, but no M. taiwanensis was found.

According to our observation, M. taiwanensis is an active terrestrial earthworm. Like M. bununa and M. paiwanna of Taiwan (Tsai et al., 2000a), it lives in the upper layer of soil and perhaps moves out to the ground surface for feeding and mating in the night and after rain. It is unlike the giant M. australis of Australia and G. giganteus of Brazil, which inhabit deep soil layers in forests or grasslands (Lee, 1985). The mountain slops of Meifeng and Mt Beidongyan, where M. taiwanensis was found, face south and south-west. They receive long hours of sunlight, so that the forest floors have a thick surface organic layer above the earth mineral layer of rocks and gravel. The surface organic layer is composed of a layer of dry, loose, undecomposed leaves, and a layer of wet leaves in various decomposed stages underneath. It is speculated that this thick surface organic layer might provide a suitable habitat for this giant terrestrial earthworm for subterranean life. In contrast, the Rueyen Nature Reserve situated north-east to Mt Beidongyan, where M. taiwanensis was not found, faces northward. It is a shady and wet area, where fallen leaves on the ground are quickly decomposed, so that the surface organic layer is thin, apparently not a favourable habitat for an earthworm of such magnitude in size.