トリイミミズ

　フトミミズ科＞アズマフトミミズ属＞ トリイミミズ Amynthas toriii (Ohfuchi, 1941)

Pheretima toriii Ohfuchi, 1941b: 244; 上平, 1973a: 57; Ishizuka, 1999a: 66; Tsai et al., 2007: 373.

Amynthas toriii Sims & Easton, 1972: 235.

タイプ標本

基産地：大分県川登村風連鍾乳洞（現：大分県臼杵市）

タイプ標本所在地：不明

形態

＜外部形態＞

　全長 37-43 mm、体幅 2.3-2.7 mm、体節数 77-83。第一背孔は第 12/13 体節間溝に開始する。

　体色は、背面と腹面の色の違いはない。

　剛毛は第 7 体節で 41-42 本、第 20 体節で 56-58 本。

　受精囊孔は 4 対で第 5/6/7/8/9 体節間溝にある。環帯は第 14-16 体節の 3 体節を占め、剛毛と体節間溝、背孔を欠く。雌性孔は第 14 体節の腹面中央に開口する。雄性孔は第 18 体節の体側にあり、楕円形の突起状で、6-8 個の円盤として突出する。雄性孔間剛毛は 7-8 本。性徴は、受精囊孔域にも雄性孔域にも全くない。

＜内部形態＞

　隔膜は第 6/7/8 体節間では薄く、第 8/9 体節間では厚く、第 9/10 体節間では欠き、第 10/11/12/13/14/15 体節間では厚い。第 11/12/13 体節間ではとても厚い。

　腸管は第 14 体節から始まる。腸盲嚢は単純状型で、第 27 体節に開口し、第 22 体節まで達する。腸盲嚢には鋸歯状の切れ込みは全くない。

　受精囊は第 6-9 体節にある。受精囊の主嚢はサクランボ型もしくはさじ型で、やや平たく、長さ 1.2 mm、幅 1 mm、導管は長さ 0.5 mm。受精囊の副嚢は湾曲せずにまっすぐで、先端は膨らみ、長い導管を形成し、全長 1.6 mm。貯精嚢は腹面中央でつながり、第 10 体節の方が大きい。精巣は第 10-11 体節にある。卵巣は 1 対で小さく、第 12/13 体節間隔膜の裏側に接する。摂護腺はよく発達し、長さ 2.3 mm、幅 1.4 mm で 3 小葉に分かれ、第 16-20 体節の 5 体節分を占める。摂護腺の導管は細く、湾曲していない。

＜原記載（クリックして展開）＞

External characters:

　　The measurements of the body and number of segments of two individuals from Furen Shonyudo Shindo are as follows:

　　The body length varies between 37-43 (40 mm in average) the width at the male genital region of XVIII varies from 2.3 to 2.7 mm (2.5 mm in average), and the number of segments varies from 77 to 83 (80 in average).

　　The colour shows no appreciable variations and no difference is noticed between the dorsal and ventral surfaces, except for the ventral surface not being as pale as is usual in other specimens. The skin is relatively thick and stiff.

　　The spermathecal openings are in four pairs in the intersegmental furrows of V/VI, VI/VII, VII/VIII and VIII/IX, and are situated in the ventro-lateral margin.

　　The clitellum occupies the 3 segments, XIV, XV and XVI without setae, intersegmental furrows and dorsal pores.

　　The setae beginning on segment II. The setal numbers of the earthworms are tabulated below (Table 1); 41-42 in VII, 56-58 in XX.

　　The openings of the male pores are in segment XVIII and are situated close to the lateral border on the slightly elevated oblong area. The margins of the pores are considerably elevated over the body surface, gradually becoming more elevated and are surrounded by the 6 or 8 oblong-shaped rings, and are separated by 7 or 8 setae.

　　Female pore single midventrally on XIV.

　　The first functional dorsal pore is found in the intersegmental furrows XII/XIII.

　　Genital papillae are not found in either the spermathecal and male pore regions.

Internal characters:

　　Spermathecae are situated in segments VI, VII, VIII and IX. The ampulla is cherry-shaped or spatulated and slightly doroventrally flattened; about 1.2 mm long, 1 mm broad in maximum and continuous to the spermathecal stalk which is about 0.5 mm long. The diverticulum is straight, much dilated at the tip, and forms a long chamber, this chamber reflects with metallic lustre, it opens in the terminal portion of the duct and is nearly equal to the combined length of duct and ampulla, being about 1.6 mm long.

　　Ovisac, one pair, it is small and hangs behind the septum XII/XIII.

　　Prostate gland well-developed, rather thin, about 2.3 mm long, 1.4 mm wide, each divided into three main lobes, and extending from XVI-XX (5 segments); muscular duct not bending and not as muscular as is usually seen in the other species of the genus, rather thin and soft, not reflecting the lustre of the tension muscle which forms the duct as is usually seen in many other species of the genus.

　　The saccular intestine originates in XIV and a pair of the intestinal caeca begin in XXVII and extend to XXII anteriorly. The caeca is a single and conical projectio, without serriformed projection in both ventral and dorsal margins, nearly smooth, with slight septal constrictions.

　　Septa generally very thin VI/VII and VII/VIII more or less thickened, VIII/IX, and IX/X lacking, X/XI, XI/XII, XII/XIII, XIII/XIV and XIV/XV more or less thickened, XI/XII and XII/XIII rather thickened.

　　The seminal vesicles barely meeting middorsally, posterior pair slightly larger than the anterior. Testis sacs in X and XI, rather large.

Remarks:

　　This species is the smallest among those possessing four pairs of spermathecae in the genus Pheretima from Japan.

　　No appreciable variations in the colour or the pigmentation were observed among the specimens living in the cavern, and no difference was noticed between the dorsal and ventral surfaces. The skin of this species is rather thick and stiff.

　　The muscular duct of the prostate gland in this species does not bend as usually seen in the other species of this genus. Presumably this species merely wandered into the caves from near by regions, or it probably was carried in with the soil from the Ponor. But in the absence of further knowledge of the Oligochaeta fauna of the exterior of this cave no conclusions can be given here.

Pheretima toriii (=Amynthas toriii) の形態 (原記載図) (Ohfuchi, 1941b p. 246, fig. 2 より)

分布

　大分県臼杵市の風連鍾乳洞に分布する。Ohfuchi (1941b) の新種記載以降、全く記録されていない。

生息環境

　風連鍾乳洞は、1.5 x 0.6 m の楕円形の入り口からすぐに 10 m のほぼ垂直の縦穴があり、その後、水平に 80 m ほど続く。この洞窟に堆積する湿った土壌に生息する (Ohfuchi, 1941b)。

備考

　Easton (1981) によりヘンイセイミミズのシノニムとされ、Blakemore (2003, 2008d, 2012b) はこの見解に従っている。

　小型であること（トリイミミズは体長 37-43 mm、ヘンイセイミミズは45-107 mm）、剛毛数が異なること（トリイミミズは第８体節に 43−45 本、第 20 体節に 56−58 本、ヘンイセイミミズは第 8 体節に 26−46 本、第 20 体節に 39−54 本）、雄性孔の周囲の皮膚の隆起数が異なり性徴を欠くこと（トリイミミズは 6〜8 層、ヘンイセイミミズは 1〜数層）、摂護腺の導管の形態が異なることから（トリイミミズは細長くまっすぐ、ヘンイセイミミズは U 字型または C 字型）、Tsai et al. (2007) により再び独立種とされた。新たな標本を採集して、分子系統学的検討を含む今後の研究が必要である。

シノニムリスト

Pheretima toriii Ohfuchi, 1941b: 244. [形態記載]

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

Pheretima toriii 上平, 1973a: 57 トリイミミズ. [同定形質のみ] (?, 1973)

Pheretima toriii Ishizuka, 1999a: 66. [記述のみ]

Pheretima toriii 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., 1941b. The cavernicolous oligochaeta of Japan. I. The Science Reports of the Tohoku Imperial University, 4th series (Biology) 16: 243-256.

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.