Amynthas ishigakiensis, 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 : 319-320

Amynthas ishigakiensis sp. nov.

( Figure 3A )

Pheretima peguana (Rosa) : Ohfuchi 1956, p. 171, text-fig. 16.

Holotype: Specimen illustrated in Ohfuchi (1956, text-fig. 16) and identified as Pheretima peguana (Rosa) . Description. All details from Ohfuchi (1956) with slight modifications. External: Body length 95–110 mm,

greatest diameter 4–5 mm, number of segments 95–120. Color in formalin, dorsally yellowish to reddish brown and ventrally much lighter, clitellum chocolate or purplish. Prostomium epilobous. Clitellum annular, extending from XIV to XVI without setae or dorsal pores but with intersegmental furrows. Setae beginning on segment II. Setal numbers: 32– 37/V, 40– 45/VI, 44– 47/VII, 46– 50/VIII and 60–66/XX, more usual setal number: 34/V, 42/VI, 45/VII, 48/VIII, 64/XX. First dorsal pore in 12/ 13 in all the specimens, sometimes with a distinct but nonfunctional pore-like depression in 11/12. Spermathecal pores three pairs in 6/7, 7/8 and 8/9, ventro-lateral. One pair of figshaped genital papillae about 0.5 mm at largest diameter near to the ventromedian line close to the male pores at anterior of the setal line. Male porophores large, eye-like, situated on the setal circle close to the lateral border of XVIII, region around each porophore glandular and very much elevated (each porophore surrounded by a whitish thick patch), separated by 13 or 15 setae.

Internal: Septa 6/7, 7/8 and 8/9 thickened, 9/10 absent, 10/11, 11/12 and 12/13 very thin. Intestine enlarged from XIV, intestinal caeca simple, originating in XXVII and extending anteriorly into about XXV, not serriformed in both ventral and dorsal margins. Three pairs of spermathecae in VII, VIII and IX. Ampulla slightly flattened in dorso-ventrally, about 2 mm in length, 1.8 or 2 mm in breadth, continuous to a very short and stout duct about 0.8 mm in length. Spermathecal diverticulum usually arising from the inner face of the spermathecal duct, much longer than the combined length of the duct and ampulla, about 1.7 mm long. Its end forming a large seminal chamber about 1.4 mm in length. The ovisac present in segment XIV. Prostate gland very large and divided into three main lobes, muscular duct long and thick, looped in U-shaped appearance and shining. The ectal end of the duct with slightly decreasing thickness passing into the body wall to open directly to the exterior through a depression as a primary male pore. Seminal vesicles well-developed in XI and XII. Testis sacs in X and XI as in other species of this genus.

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

Remarks. M. peguana has male pores each within a transversely slit-like lumen ( Gates 1972), two pairs of large, round genital markings across 17/18 and 18/19, coiled or S-shaped prostatic ducts confined to segment XVIII, and diverticulum with a heavily twisted stalk (Rosa 1 890, Figs. 6–8). However, specimens from Ishigaki Island, the Ryukyus described by Ohfuchi (1956) as " Pheretima peguana " have superficial male pore in large eyelike male porophore surrounded by whitish, thick and elevated skin, one pair of presetal genital papillae in the male pore region, long, U-shaped prostatic duct occupying about two segments, and diverticulum with a simple, long stalk and a large seminal chamber ( Ohfuchi 1956, p. 172, text-fig. 16). Consequently, the correct identity of Ohfuchi's (1956) specimens certainly is not M. peguana . Also, no similarity is found when compared with the other members of Amynthas having three pairs of spermathecal pores in 6/7–8/9. 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).

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.