ハトマミミズ

　フトミミズ科＞アズマフトミミズ属＞ハトマミミズ Amynthas hatomajimensis (Ohfuchi, 1957)

Pheretima hatomajimensis Ohfuchi, 1957a: 245; 上平, 1973a: 56.

Amynthas hatomajimensis Sims & Easton, 1972: 235; Tsai et al., 2007: 373.

Pheretima hatomajimaensis [sic] Ishizuka, 1999a: 59.

タイプ標本

基産地：鳩間島

タイプ標本所在地：不明（紛失？）(Reynolds & Cook, 1976)

形態

＜外部形態＞

　全長 73-94 mm、体幅 3-4.5 mm、体節数 75-93。

　体色は背面は暗褐色で、腹面は明灰色。環帯はピンク色味を帯びる。

　剛毛は第 7 体節で 41-46 本、第 20 体節で 60-65 本。背面・腹面とも剛毛の断絶がはっきりしている。第一背孔は第 12/13 体節間溝。

　環帯は第 14-16 体節の 3 体節を占め、背孔や体節間溝、剛毛を欠く。雄性孔は第 18 体節で、雄性孔は体表から明らかに盛り上がる。雄性孔間距離は体周の 1/3 程度。雄性孔間剛毛は 11-15 本。受精囊孔は第 5/6/7/8/9 体節間溝で、受精囊孔間距離は体周の 1/3 程度。雄性孔に隣接して雄性孔円盤上に 3 つの性徴があり、剛毛線前後と剛毛線上にある。なお、図から雄性孔を含めて性徴が十字型に配置される。また、本文には記述されていないものの、図には雄性孔円盤から外れて内側の剛毛線より後ろ側にももう 1 対の性徴が描かれている。受精囊孔域には性徴を欠く。

＜内部形態＞

　隔膜は第 6/7/8/9 体節間はかなり厚く、第 9/10 体節間で欠き、第 10/11/12 体節間ではやや厚く、第 12/13/14 体節間では薄い。

　腸管は第 13 体節もしくは第 15 体節から始まり、腸盲嚢は突起状で鋸歯状の小突起を欠き、第 26 体節から第 23 体節まで伸びる。

　受精囊は 4 対で、第 5-9 体節に存在する（記載分ではこのように記述されているが、これでは 5 対になるため、第 6-9 体節の誤りであろう）。受精囊の主嚢は長洋梨形で、やや平たく、長さ 3.5 mm、幅 2 mm で、導管は長さ 1.3-2 mm。副嚢は長さ 2.5 mm で、細長く、先端は球状に膨らむ。貯精嚢は第 11-12 体節で、よく発達する。摂護腺は第 17-22 体節までの 6 体節を占める。摂護腺の導管は太く、U 字型に湾曲する。摂護腺孔は直接外部に開口し、この開口部が記述のない性徴に見える部分（第 18 体節の雄性孔円盤から外れて剛毛線より後ろ側）かも知れない。生殖腺は見当たらなかった。

＜原記載（クリックして展開）＞

Locality: Hatoma-jima, Iriomote, on April 1, 1936. Collected by members of expedition to Riu-Kiu Island by Dr. Yamashina.

External characters: The body length from 73-94 mm, the greatest diameter from 3-4.5 mm, the number of segments varies from 75-93.

The skin very thin, the colour is dark brown on the dorsal surface, and light grey on the ventral surface, clitellum pinkish. Prostomium epilobous. The clitellum is annular and extends from XIII/XIV to XVI/XVII. Dorsal pores, intersegmental furrows and setae lacking.

The first dorsal pore in XII/XIII.

The setae begins on segment II, prominent on ventral side of anterior segments, ventral setae of III-IX noticeably long and widely spaced. Both dorsal and ventral breaks are very distinct. The setal numbers are as follows; 32-38/V, 36-39/VI, 41-46/VII, 45-49/VIII, 60-65/XX.

The spermathecal pores, four pairs in intersegmental furrows V/VI, VI/VII, VII/VIII and VIII/IX ventro-lateral in position, about 1/3 of body circumference apart. No genital papillae are found near this region.

The male pores situated on setal circle close to lateral border of segment XVIII, about 1/3 of circumference apart, separated by 11-15 setae. The margin of the porophore is considerably elevated over the body surface and contain three small circular genital papillae. The papillae are situated within the elevated area, its surface glandular and smooth. These genital papillae are found in the neighborhood of the male pores in anterior, posterior and on setal line.

Internal characters: Septa VI/VII, VII/VIII and VIII/IX very much thickened, IX/X absent, X/XI and XI/XII more or less thickened, XII/XIII and XIII/XIV thin.

Pharyngeal glands thick and soft surrounding coelomic surface of pharynx. Intestine begins in XIII or XV and a pair of intestinal caeca commences in XXVI, and extend to XXIII anteriorly. It is a simple sac, straight and nearly smooth not serriformed on the both ventral and dorsal margins.

Spermathecae, situated four pairs in V, VI, VII, VIII and IX. Ampulla elongate pear-shaped, smooth and slightly flattened in dorsoventrally about 3.5 mm in length, 2 mm in breadth and continuous to the ampullary duct which is about 1.3 or 2 mm in length, rather long, usually marked off from the later. The spermathecal diverticulum usually arises from the inner face of the spermathecal duct about 2.5 mm in length a long slender and straight swallen in the end, which is ovoid or elongate spherical in shape and forming a seminal chamber.

Ovaries, one pair of small tuft-shaped.

The prostate gland moderate in size and development, extends from XVII anterior to XX posteriorly, glandular parts of both sides nearly enveloped dorsally. Prostate duct larger at its middle part, U-shaped, coiled at both ends distal end slender, directly opening into the outside. Accessory glands not found in this region the genital papillae which are on external porophore not associated with the gland internally.

The seminal vesicles lie in segments XI and XII, are very well developed compared with other species of the genus, covered through the half of gizzard. Testis large, round and pyriform, placed at anterior outer corner of each sac.

Remarks: In some respects, it is closely related to Pheretima pingi, in number of spermathecae and aspect of the genital papillae of the male pore region, but in later, spermathecal pore transversely situated on posterior side of oval papilla which is flat-topped, distinctly raised as large as other genital papillae or inconspicuous as a small tubercle, usually close to posterior margin of preceding segment, or occasionally posterior to intersegmental furrow, but each pore always situated intersegmentally. But in this present new species, each spermathecal pore opens in intersegmental furrows, of preceding segment. At the same time, in former species, the genital papillae beside those near pores less constantly present, often paired on segments VIII and IX, and those on VIII placed either ante- or post-setally if only one pair is present, whereas if two pairs present, they are on both sides of setal; one or occasionally two pairs on IX are generally ante-setally. But the present new species has no genital papillae near the spermathecal region. And in the former species, the semitransparent saccules which were found on the ampullar duct of the original type are rather rare a hundred specimens present such structures. These saccules may also be found on the ampulla and diverticulum. But in present new species, no such saccules are found in these ampullar duct.

Therefore, in the former species accessory glands found in the near of the prostatic duct which corresponding to external papillae. Each papilla associated with one gland internally which roundish and granular of surface. But in this present new species, these glands are not found in this region.

備考

　Easton (1981) や Blakemore (2012e) によって疑問符付きで、Blakemore (2003) によって括弧と疑問符付きでヘンイセイミミズのシノニムとされた。しかし、雄性孔域の性徴の形態が異なるため、Tsai e tal. (2007) により再び独立種とされた。

シノニムリスト

Pheretima hatomajimensis Ohfuchi, 1957a: 245. [形態記載]

Amynthas hatomajimensis Sims & Easton, 1972: 235. [記述のみ] (Sep ?, 1972)

Pheretima hatomajimensis 上平, 1973a: 56 ハトマミミズ. [同定形質のみ] (?, 1973)

Pheretima hatomajimaensis [sic] Ishizuka, 1999a: 59. [記述のみ]

Amynthas hatomajimensis Tsai et al., 2007: 373. [特徴指摘]

引用文献

Blakemore, R.J., 2003. Japanese earthworms (Annelida: Oligochaeta): A review and checklist of species. Organisms Diversity and Evolution 11: 1-43.

Blakemore, R.J., 2008d. A review of Japanese earthworms after Blakemore (2003). In: Ito MT, Kaneko N, (eds.), A Series of Searchable Texts on Earthworm Biodiversity, Ecology and Systematics from Various Regions of the World, 2nd Edition (2006) and Supplemental. COE soil Ecology Research Group, Yokohama National University, Japan. CD-ROM Publication.

Blakemore, R.J., 2012b. Japanese earthworms revisited a decade on. Zoology in the Middle East 58 suppl 4: 15-22.

Easton, E.G., 1981. Japanese earthworms: A synopsis of the Megadrile species (Oligochaeta). Bulletin of the British Museum Natural History (Zoology) 40(2): 33-65.

Ishizuka, K., 1999a. A review of the genus Pheretima s. lat. (Megascolecidae) from Japan. Edaphologia (62): 55-80.

上平幸好, 1973a. 日本産陸棲貧毛類フトミミズ属(Genus Pheretima), 種の検索表. 函館大学論究 7: 53-69.

Ohfuchi, S., 1957a. On a collection of the terrestrial oligochaeta obtained from the various localities in Ryu-Kiu Islands, together with the consideration of their geographical distribution (Part 2). Journal of Agricultural Science, Tokyo Nogyo Daigaku 3(2): 243-261.

Reynolds, J.W., Cook, D.G., 1976. Nomenclatura Oligochaetologica: A Catalogue of Names, Descriptions and Type Specimens of the Oligochaeta. University of New Brunswick, Fredericton, Canada. 217 pp.

Sims, R.W., Easton, E.G., 1972. A numerical revision of the earthworm genus Pheretima auct. (Megascolecidae: Oligochaeta) with the recognition of new genera and an appendix on the earthworms collected by the Royal Society North Borneo Expeditions. Biological Journal of the Linnean Society 4: 169-268.

Tsai, C.F., Shen, H.P., Tsai, S.C., Lee, H.H., 2007. Four new species of terrestrial earthworms belonging to the genus Amynthas (Megascolecidae: Oligochaeta) from Taiwan with discussion on speculative synonyms and species delimitation in oligochaete synonymy. Journal of Natural History 41(5-8): 357-379.