ソナイミミズ

　フトミミズ科＞フクロフトミミズ属＞ソナイミミズ Metaphire sonaiensis (Ohfuchi, 1956)

Pheretima sonaiensis Ohfuchi, 1956: 154; 上平, 1973a: 60; Ishizuka, 1999a: 65.

Metaphire sonaiensis Sims & Easton, 1972: 239.

タイプ標本

基産地：西表島祖納

タイプ標本所在地：消失？ (Reynolds & Cook, 1976; Blakemore, 2003)

形態

＜外部形態＞

　全長 70-84 mm、体幅 2.5-3 mm、体節数 85-110.

　フォルマリン液浸標本の体色は、背面は褐色で、腹面は淡褐色または白色。環帯は褐紫色。

　剛毛は第 5 体節で 16-20 本、第 6 体節で 23-28 本、第 7 体節で 28-32 本、第 8 体節で 35-40 本、第 20 体節で 51-55 本。第一背孔は第 12/13 体節間溝。

　環帯は第 14-16 1/2 体節もしくは第 14-16 体節を占める。雄性孔は第 18 体節に開口し、雄性孔の縁は体表からやや盛り上がる。なお、原記載の本文には雄性孔の形態については記述されていないが、図にははっきりと陥没状型雄性孔が描かれている。雄性孔間剛毛は 13 本。受精囊孔は 2 対で第 7/8/9 体節間溝。性徴を欠く。

＜内部形態＞

　隔膜は、第 6/7/8/9 体節間ではかなり厚い。

　腸管は第 15 体節から開始する。腸盲嚢は突起状型で、第 27 体節にあり、第 23 体節まで伸びる。

　受精囊は第 8-9 体節にあり、主嚢は洋梨形で細長く、長さ 2 mm、幅 0.6 mm。主嚢の導管は短くて頑強。受精囊の副嚢はねじ曲がるが、先端は楕円形に膨れる。卵巣は 1 対。精巣は第 10-11 体節。貯精嚢はよく発達し、第 11-12 体節。摂護腺はよく発達し、第 15-21 体節の 7 体節を占め、2-4 個の小嚢に別れ、さらに細分化される。摂護腺の導管は半分までは太くて膨れ、残りの部分は細くてややねじれる。

＜原記載（クリックして展開）＞

Locality: Sonai, Iriomote. Collected by members, expedition at the instigation of Marquis Yamashina, on March 26, 1935.

External characters:

The body length from 70-84 mm, the greatest diameter from 2.5-3 mm, the number of segments varies from 85-110.

The colour of this worm in formalin, brownish dorsally, pale brownish or whitish elsewhere, clitellum brownish purple, extending from XIV to 1/2 of XVI orXIV to XVI. Dorsal pores, intersegmental furrows and setae lacking.

The setae begins on segment II, the setal numbers are as follows: 16-20/V, 23-28/VI, 28-32/VII, 35-40/VIII, 51-55/XX, more usual setae number: 16/V, 25/VI, 30/VII, 37/VIII, 54/XX.

Clitellum embracing segments VIX-XVI., unprovided with intersegmental furrows. The setae are wanting on the clitellum.

The first dorsal pore in XII/XIII: Prostomium, epilobous or tanylobous.

The spermathecal pores; two pairs in VII/VIII and VIII/IX, ventrolateral in position. No genital papillae in the bound near this region.

The male pores situated on setae circle close to lateral border of segment XVIII, separated by 13 setae. The margin of the male proofer is slightly elevated over the body surface.

Internal characters:

Septa VI/VII, VII/VIII and VIII/IX very much thickend [sic].

Intestine begins in XV and a pair of intestinal caeca commences in XXVII and extends to XXIII anteriorly, not serriformed on both ventral and dorsal margins.

Two pairs spermathecae are situated in VIII and IX. Ampulla pear-shaped long and slender, about 2 mm in length, 0.6 mm in breadth and continuous to the ampullary duct, the duct very short and stout.

The spermathecal diverticulum usually arises from the inner face of the spermathecal duct, twisted in middle region has a straight and much dilated tip and is composed of a thick-walled stalk with a narrow lumen and an mental end is well distended, forming an ovoidal long seminal chamber.

Ovaries, one pair of small tuft-shaped ovaries.

The prostate gland are very well developed extending through the segments XV-XXI, divided in about three or four lobes and subdivided in small many pieces. The duct forms the boundary in two parts at middle region, the part of gland is much dilated and is composed of a thick-walled, and other remaining part become slender and loosely coiled distally.

The Seminal vesicles are well developed and are situated in XI and XII. Testis sacs in X and XI.

Habitate: The intestinal contents of the all Sonai-worms are brownish in colour, this is indicating that the worms like the dwelling in sandy soil.

分布

　原記載以降の採集記録は見当たらない。タイプ標本は西表島で得られている (Ohfuchi, 1956)。

備考

　Easton (1981) は疑問符付きでメキシコミミズのシノニムとし、Blakemore (2003, 2008d) は括弧と疑問符付きで、Blakemore (2012b) は疑問符無しでメキシコミミズのシノニムとした。

　腸盲嚢が突起状型であること（メキシコミミズは鋸歯状型）、第一背孔が第 12/13 体節間溝（メキシコミミズは第 11/12 体節間溝）であることから、独立種であると考えられる。本種のタイプ標本が失われたため、基産地で新たな個体を得て詳細な検討が必要である。

シノニムリスト

Pheretima sonaiensis Ohfuchi, 1956: 154. [形態記載]

Metaphire sonaiensis Sims & Easton, 1972: 239. [記述のみ]

Pheretima sonaiensis 上平, 1973a: 60. [同定形質のみ]

Pheretima sonaiensis Ishizuka, 1999a: 65. [記述のみ]

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., 1956. 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 1). Journal of Agricultural Science, Tokyo Nogyo Daigaku 3(1): 131-176.

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.