リュウキュウミミズ

　フトミミズ科＞フクロフトミミズ属＞リュウキュウミミズ Metaphire riukiuensis (Ohfuchi, 1957)

Pheretima riukiuensis Ohfuchi, 1957a: 248; 上平, 1973a: 56; 中村, 1998: 26; Ishizuka, 1999a: 64.

Metaphire riukiuensis Sims & Easton, 1972: 238; Easton, 1981: 58; Blakemore, 2003: 33, 2008d: 126, 2012b: 19.

タイプ標本

基産地：西表島祖納と干立、鳩間島、石垣島の宮良（Miyara）

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

形態

＜外部形態＞

　全長 219-270 mm、体幅 8-10 mm、体節数 135-138。

　体色は背面は環帯までは灰青色で、環帯以後は赤褐色から褐色。環帯は灰色。

　剛毛は第 7 体節で 72-74 本、第 20 体節で 48-51 本。第 20 体節以降では剛毛数は少ない。背面の剛毛は短く、腹面では長い。背面と腹面の剛毛の断絶がはっきりしている。第一背孔は第 12/13 体節。

　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 体節の剛毛線上にあり、それぞれの雄性孔は分厚い唇状の裂け目の中に開口する。雄性孔間距離は体周の 1/3。雄性孔間剛毛は 5-6 本。受精囊孔は 4 対で、第 5/6/7/8/9 体節間溝にあるが、目立たない。性徴を欠く。

＜内部形態＞

　隔膜は第 5/6/7/8 体節間でとても厚く、第 8/9/10 体節間で欠く。隔膜は一般的にとても厚い。

　腸管は第 14 もしくは 16 体節から開始し、腸盲嚢は鋸歯状型で腹側のみに 4-5 個の小突起があり、第 27 体節から第 24 体節まで伸びる。

　受精囊は 4 対で第 6-9 体節にある。受精囊は大きく、長さ 3.5 mm、幅 3 mm で、受精囊導管は長さ 1.5 mm。受精囊の副嚢は主嚢と同長かより長いで、長さ 5 mm。副嚢の基半分は細くてねじれ、先半分はやや膨らむ。幾つかの個体では、副嚢が不定形で 2 本以上あった。貯精嚢は中程度に発達し、 2 対で第 11-12 体節。摂護腺は中程度のサイズで、4 つの嚢状部に別れ、更に細分化される。摂護腺の導管は太くて筋肉質で、直線的。

＜原記載（クリックして展開）＞

Locality: Sonai, Iriomote. Hoshidate, Hatomajima, Miyara, Ishigaki. On March 22, 1936. Collected by the members of an expedition to Riu-kiu Islands. And also collected by Dr. Hanzawa Professor of Tohoku University June 1931.

External characters: Length 219-270 mm, the greatest diameter is 8-10 mm, number of segments of one complete specimen, 135-138. Colour of the dorsum anterior of the clitellum, greywish blue; posterior to the clitellum, reddish brown to brownish; clitellum greywish. Prostomium epilobous or tanylobous. The clitellum is annular and smooth, occupying three full segments, XIV-XVI; without dorsal pores, intersegmental furrows and setae.

The first dorsal pore is in XII/XIII.

The setae begin on II and are small and closely crowded. The setal numbers; 61-64/V, 63-65/VI, 72-74/VII, 74-76/VIII, 48-51/XX. Setae on dorsal side shorter, ventral side longer, middorsal and midventral breaks are very distinct.

The spermathecal opening, four pairs in intersegmental grooves V/VI, VI/VII, VII/VIII and VIII/IX, the pores indistinct in ventral side. No genital papillae in the spermathecal region.

The male pores situated on setal line close to lateral border of XVIII about 1/3 of the circumference apart and separated by 5-6 setae, and the midventral break is clearly visible at this place, each aperture opened in the large thick lips which are on the right and left side of the apertures, and the apertures embraces in these lips.

Internal characters: Septa V/VI, VI/VII, VII/VIII very thick, VIII/IX and IX/X absent, the septa in generally are very thick.

Intestine begins in XIV or XVI, intestinal caeca simple, originating in XXVII and extending anteriorly into about XXIV with 4-5 serriformed in the ventral edge and without in the dorsal edge.

Spermathecae, anterior pair lying in VI, last 4th pair in IX. Ampulla large about 3.5 mm in length, 3 mm in width, and continuous to muscular duct which is about 1.5 mm in length. The spermathecal diverticulum usually arises from the inner face of the spermathecal duct, always longer than the ampulla, usually nearly equal in length to the combined the muscular duct and ampulla, its ectal half rather slender, simple and twisted, and the ental remaining slightly dilated and forming an ovoidal shaped seminal chamber of 5 mm in total length. In some specimen, two or more diverticula fused together and a large irregular shape.

Ovaries in usual position. Oviduct-funnel in front of septum XIII/XIV.

The prostate gland moderate in size, divided into four main lobes, and subdivided into many small lobes, muscular duct almostly straight not bending as usually found in other species.

The seminal vesicles, two pairs in XI and XII, both pairs in moderate in size, which are usually found in many species of this genus.

Remarks: The tendency in this species is that the setal number gradually in anteclitellar segment but suddenely decreases in segment XX. This tendency usually observed in the earthworms of South Sea Islands but not so in Japanese forms.

The present new species shows close resemblance to Pheretima formosae Michaelsen in some external characters, especially, bigness in size, but easily be distinguished by the following characters, for instance, the male pore of Pheretima formosae described only "Mannliche Poren, ......auf grozen Porophorean mit konzentrischen Kreis furchen" but in this present new species, the male aperture opened in the large thick lips which are on the right and left side of the apertures and the apertures embraced with this lips in their inside.

The appearance of the prostate gland in this new species very specialize.

分布

　先島諸島の西表島、鳩間島、石垣島から得られている。新種記載以後の記録は見当たらないが、最近、石垣島で採集した (南谷, 未発表データ)。

シノニムリスト

Pheretima riukiuensis Ohfuchi, 1957a: 248. [形態記載]

Metaphire riukiuensis Sims & Easton, 1972: 238. [記述のみ] (Sep ?, 1972)

Pheretima riukiuensis 上平, 1973a: 56. [記述のみ]

Metaphire riukiuensis Easton, 1981: 58. [記述のみ] (Apr 30, 1981)

Pheretima riukiuensis 中村, 1998: 26 リュウキュウミミズ. [記述のみ]

Pheretima riukiuensis Ishizuka, 1999a: 64. [記述のみ]

Metaphire riukiuensis Blakemore, 2003: 33. [同定形質のみ] (?, 2003)

Metaphire riukiuensis Blakemore, 2008d: 126. [同定形質のみ] (Dec ?, 2008)

Metaphire riukiuensis Blakemore, 2012b: 19. [記述のみ] (Feb 28, 2012)

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.

中村好男, 1998. ミミズと土と有機農業. 創森社, 123 p.

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.