Amynthas quadriorbis Shen and Chang

Shen, Huei-Ping, Chang, Chih-Han & Chih, Wen-Jay, 2016, Four new earthworm species of the genus Amynthas (Megascolecidae: Oligochaeta) from southwestern Taiwan with re-description of Amynthas tungpuensis Tsai, Shen and Tsai, 1999, Journal of Natural History 50 (29 - 30), pp. 1889-1910 : 3-7

Amynthas quadriorbis Shen and Chang , sp. nov.

( Figure 2 )

Type material

Holotype. Clitellate (107 mm in length, dissected) collected 17 July 2007 from roadside slope along Waihu Creek (elevation 230 m) near the borders of Douliou and Linnei, Yunlin by C.H. Chang, T.J. Lin and Y.H. Lin (TESRI-O-H-47) (voucher number: WH3P1).

Paratype. One clitellate collected 15 August 2007 from type locality by C.H. Chang, Y.H. Lin and Y.P. Li (TESRI-O-P-42).

Diagnosis

Medium earthworm; length (clitellates) 107 – 120 mm. Segments numbering 103 – 129. Setae 60 – 68 in VII, 73 – 76 in XX and 15 – 18 between male pores. Clitellum XIV – XVI. First dorsal pore in 11/12. Spermathecal pores invisible or small, three pairs in 6/7 – 8/9, 0.29 – 0.30 body circumference ventrally apart. Genital papillae absent in preclitellar region. Male pores 0.24 body circumference ventrally apart in XVIII, each on a round porophore surrounded by two to four circular or diamond-shaped shallow skin folds. Two large genital papillae medial to each male porophore: one immediately adjacent to intersegmental furrow of 17/18 and the other to 18/19. Spermathecae small, three pairs in VII – IX.

Seminal vesicles small, two pairs in XI and XII, occupying two-thirds of segmental compartment, each vesicle with a prominent, round or oval dorsal lobe. Prostate glands small in XVII – XVIII. Prostatic duct stout, C-shaped. Accessory glands absent.

Description

External characters. Total length (clitellates) 107 – 120 mm. Weight 1.19 – 1.54 g. Segments numbering 103 – 129. Clitellum XIV – XVI, setae and dorsal pores absent, length 3.65 – 4.59 mm and width 3.83 – 4.21 mm. Prostomium epilobous. Setae minute, numbering 60 – 68 in VII, 73 – 76 in XX and 15 – 18 between male pores in XVIII. First dorsal pore in 11/12. Spermathecal pores invisible or small, three pairs in intersegmental furrows of 6/ 7 – 8/9; distance between paired pores 0.29 – 0.30 body circumference ventrally apart. Genital papillae absent in the preclitellar region. Female pore single, mid-ventral in XIV. Male pores paired in XVIII, about 0.24 body circumference ventrally apart, each on a round porophore surrounded by two to four circular or diamond-shaped shallow skin folds. Two large genital papillae medial to each male porophore: one presetal and the other postsetal with the former immediately adjacent to intersegmental furrow of 17/18 and the latter to 18/19, both confined in segment XVIII, 0.45 – 0.60 mm in diameter with depressed centre ( Figure 2 a).

Preserved specimens brown on dorsum, brown to greyish brown on clitellum, and greyish on ventrum.

Internal characters. Septa 5/6 – 7/8 thick, 10/11 – 13/14 muscular, 8/9/10 absent. Nephridial tufts on anterior faces of 5/6/7. Gizzard large in VIII – X. Intestine enlarged from XVI. Intestinal caeca paired in XXVII, extending anteriorly to XXII, each long, simple, stout, slightly bent. Oesophageal hearts in XI – XIII.

Spermathecae small, three pairs in VII – IX (sexthecate) ( Figure 2 b). Each ampulla pearshaped or elongated oval-shaped, 0.56 – 1.03 mm long and 0.40 – 0.70 mm wide, with a slender or stout spermathecal stalk 0.35 – 0.58 mm in length. Diverticulum with an iridescent, oval-shaped seminal chamber of 0.25 – 0.50 mm long and a slender stalk of 0.60 – 0.68 mm in length. Accessory glands absent in the preclitellar region.

Holandry: testes small, oval, two pairs in ventrally joined sacs in X and XI. Seminal vesicles small, transversely elongated, two pairs in XI and XII, occupying two-thirds of segmental compartment, each vesicle with a prominent, round or oval dorsal lobe. Prostate glands small in XVII – XVIII, smooth, lobed, flower-like. Prostatic duct stout, C-shaped ( Figure 2 c). Accessory glands absent.

DNA barcode

GenBank accession number KU232820 (WH3P1, holotype).

Etymology

The name quadriorbis refers to the four large genital papillae in the male pore region.

Remarks

Amynthas quadriorbis sp. nov. is only known from its type locality in the foothills at elevations <250 m near Douliou, Yunlin, southwestern Taiwan. According to Tsai et al. (2004), the number of native earthworm species decreased while the number of exotic species increased with decreasing elevation, and this species shift is primarily attributable to habitat replacement due to human disturbance. Nowadays only seven native species, Metaphire formosae ( Michaelsen, 1922) , Amynthas swanus ( Tsai 1964) , Amynthas binoculatus Tsai, Shen and Tsai, 1999 , Amynthas sexpectatus Tsai, Shen and Tsai, 1999 , Amynthas tungpuensis Tsai, Shen and Tsai, 1999 , Metaphire bununa Tsai, Tsai and Liaw, 2000 and Amynthas penpuensis Shen, Tsai and Tsai, 2003 , were found at elevations below 500 m in centro-western Taiwan with A. swanus being the rarest ( Tsai et al. 2004 and unpublished data, H.-P. Shen). The fact that A. quadriorbis has only been found in one location throughout the extensive surveys conducted in the region in the last decade suggests that A. quadriorbis is also rare. With their habitat subjected to intensive agricultural activities, both A. swanus and A. quadriorbis may be considered as an endangered species.

Amynthas quadriorbis has three pairs of spermathecal pores in intersegmental furrows of 6/7 – 8/9, and so belongs to the holandric, sexthecate sieboldi species-group of the genus Amynthas ( Sims and Easton 1972) . Among the members of the sieboldi -group, the peregrine Amynthas hupeiensis ( Michaelsen, 1895) from China and Amynthas obscurus ( Goto and Hatai, 1898) from Japan have a genital papilla arrangement in the male pore area similar to A. quadriorbis . However, A. hupeiensis has paired genital papillae in the intersegmental furrows of 17/18 and 18/19 ( Chen 1933; Tsai 1964), much higher setal number than A. quadriorbis with 100 – 121 in VIII and 79 – 88 in XX ( Tsai 1964) and very long diverticula ( Chen 1933; Tsai 1964). Amynthas obscurus is smaller (80 mm long with 76 segments), has an additional pair of papillae in postsetal XIX, and has much lower setal number with 35 – 38 in the spermathecal segments ( Goto and Hatai 1898).

The arrangement of genital papillae in the male pore area of A. quadriorbis is also similar to that of Amynthas modiglianii ( Rosa 1889) from Nias, Indonesia, Amynthas micronarius ( Goto and Hatai, 1898) from Japan, and Amynthas tetrapapillatus Quan and Zhong, 1989 from Hainan Island, China. Amynthas modiglianii is an octothecate earthworm with four pairs of spermathecal pores in intersegmental furrows of 5/6 – 8/9 and has coiled diverticula ( Rosa 1889; Michaelsen 1934). Amynthas micronarius is also octothecate without diverticula or with minute diverticula, and has much lower setal number than A. quadriorbis with 26 – 39 in VII and 33 – 51 in XX ( Ohfuchi 1937) and welldeveloped prostate glands ( Goto and Hatai 1898; Ohfuchi 1937). As for A. tetrapapillatus , it has paired genital papillae in the intersegmental furrows of 17/18 and 18/19, a pair of spermathecal pores on the dorsal side of the intersegmental furrow of 5/6, and much higher setal number than A. quadriorbis with 93 – 107 in VII and 86 – 102 in XX ( Quan and Zhong 1989).

Figures

Figure 2. Amynthas quadriorbis sp. nov. Holotype (TESRI-O-H- 47) (voucher number: WH 3 P 1). (a) Ventral view of male pore region (gp, genital papilla; mp, male porophore). (b) Dorsal view of right spermathecae (amp, ampulla; dv, diverticulum). (c) Dorsal view of right prostate gland (pd, prostatic duct). Scale bar 1 mm.