Amynthas iriomotensis, Shen, 2018

Shen, Huei-Ping, 2018, Biogeography meets taxonomy: Distribution-based inferences on the accuracy of identification and synonymization of East Asian earthworms, Zootaxa 4496 (1), pp. 313-336 : 320-322

Amynthas iriomotensis sp. nov.

( Figure 3B )

Pheretima leucocirca Chen : Ohfuchi 1956, p. 174, text-fig. 17.

Holotype: Specimen illustrated in Ohfuchi (1956, text-fig. 17) and identified as Pheretima leucocirca Chen.

Description. All details from Ohfuchi (1956), with slight modifications. External: Body length 130–155 mm, greatest diameter 5–6 mm, number of segments 110–130. Color in formalin, brownish dorsally and ventrally lighter than the dorsal, clitellum light chocolate. Prostomium epilobous. Clitellum annular, in XIV–XVI, without setae or dorsal pores. Setae beginning on segment II, setal numbers: 29– 33/V, 34– 38/VI, 42– 46/VII, 46– 48/VIII, 55–60/XX. Ventral setae longer than the dorsal ones, midventral break distinct, no difference in length and interval between dorsal and ventral ones. First dorsal pore in 11/12 or 12/13. Spermathecal pores three pairs in 6/7, 7/8 and 8/9, ventro-lateral, the openings very distinct. No genital papillae found near this region. Male pores on ventrolateral extremities of XVIII, in setal line, about 1/3 body circumference ventrally apart, the porophore a teat-like protuberance with several circular wrinkles around. Male openings characteristic: in XVIII the male pore situated at the extreme lateral side within a large round elevated disc, two round papillae immediately medial to each male pore, one presetal and the other postsetal, projecting prominently from the body surface. Number of setae between male pores 14 or 16.

Internal: Septa 6/7, 7/8 and 8/9 much thickened, 9/10 absent, 10/11, 11/12 and 12/13 thin. The septum usually thin. Intestine enlarged from XVI, intestinal caeca simple, originating in XXVII, extending anteriorly to XXIV, not serriformed in both ventral and dorsal margins. Three pairs of spermathecae in VII, VIII and IX. Ampulla slightly flattened in dorso-ventrally, about 3 mm in length, 2 mm wide, continuous to the very short and stout duct. Spermathecal diverticulum with its end forming a large seminal chamber about 2 mm in length. Three or four capsulogenous glands near the spermathecae. Prostate gland very large, extending from XVI to XX, and divided into three main lobes, muscular duct very long, bending into ear-capsule-like shape. Seminal vesicles welldeveloped in XI and XII. Testis sacs in X and XI as in the other species of this genus.

Etymology. The name iriomotensis is given to this species with reference to its type locality in Iriomote Island, the Ryukyus.

Remarks. Specimens from Iriomote, the Ryukyus described by Ohfuchi (1956) as " Pheretima leucocirca " are fairly similar to Amynthas leucocircus ( Chen, 1933) from central China in body size, segment number, setal number, papilla arrangement around male pore and in having three pairs of spermathecal pores in 6/7–8/9. However, A. leucocircus has pre-clitellar genital papillae in postsetal, medio-ventral position in VII and VIII, small seminal vesicles, short and stout prostatic duct confined to segment XVIII, large, compact, round or kidney-shaped accessory gland associated with each papilla, and short diverticulum ( Chen 1933, Figs. 22 & 23), whereas Ohfuchi's (1956) specimens have no pre-clitellar genital papillae and have well-developed seminal vesicles, long, U-shaped prostatic duct occupying about two segments, and long diverticulum ( Ohfuchi 1956, p. 175, text-fig. 17). Ohfuchi (1956) mentioned accessory glands (= capsulogenous glands) in the spermathecal region but not in segment XVIII and hence, glands might be absent or too small to be noticed in segment XVIII. These specimens were uncertainly considered synonymous with A. flavescens by Easton (1981) and Blakemore (2003; 2012b), but the presence or absence of papillae in the pre-clitellar region, papilla arrangement in the male pore region and the structure of diverticulum are different ( Table 2). No other members of Amynthas having three pairs of spermathecal pores in 6/7–8/9 are more similar to Ohfuchi's (1956) specimens than A. leucocircus . Ohfuchi's (1956) specimens should belong to a new species. The whereabouts of the type material is currently unknown. The designation of the holotype is in accordance with the rules of the International Code of Zoological Nomenclature (Articles 72.5.6. and 73.1.4.) ( ICZN 1999).

1 Ph. vieta in Kobayashi (1941) .

Figures

FIGURE 3. Amynthas ishigakiensis sp. nov. (A) and Amynthas iriomotensis sp. nov. (B). A. Text-fig. 16 in Ohfuchi (1956). 1. Ventral view of the genital marking on the right side of the segment XVIII. 2. Prostate gland with its duct. 3. Spermatheca and the ampulla. 4. Intestinal caecum in lateral view from the left side. B. Text-fig. 17 in Ohfuchi (1956). 1. Ventral view of the genital marking on the right side of the segment XVIII. 2. Intestinal caecum in lateral view from the left side. 3. Prostate gland with its duct. 4. Spermatheca, ampulla and its neighboring capsulogenous glands.