Polypheretima taprobanae

　フトミミズ科＞ネッタイフトミミズ属＞ Polypheretima taprobanae (Beddard, 1892)

Perichaeta taprobanae Beddard, 1892: 163, 1895: 411.

Amyntas taprobanae Beddard, 1900: 648.

Pheretima taprobanae Michaelsen, 1900: 308; Stephenson, 1923: 312; Aiyer, 1929: 72; Gates, 1937a: 209, 1960c: 278, 1976c: 2; Sawar et al., 2006: 4.

Metapheretima taprobanae Mischis & Herrera, 2006: 287.

Polypheretima taprobanae Easton, 1982: 734; Nguyen et al., 2014: 117; Reynolds, 2015v: 119.

Pheretima taprobanae pauli Michaelsen, 1900: 309.

形態

＜外部形態＞

　体長 80-105 mm (80-105 [原記載]、105 [Shen & Yeo, 2005])、体幅 6.5 mm (Shen & Yeo, 2005)、生重 1.61g (Shen & Yeo, 2005)。体節数 114-122 (114 [原記載]、122 [Shen & Yeo, 2005])。体前部ではしばしば二次環節が生じ (原記載)、第 6 体節以後3つの二次環節が存在する (Shen & Yeo, 2005)。

　体色は液浸標本では背面は淡灰色で、腹面は明灰色、環帯は淡灰色 (Shen & Yeo, 2005)。第 1-5 体節は白色 (Shen & Yeo, 2005)。

　剛毛は第 1 体節で 52 本、第 5 体節で 81 本、第 12 体節で 74 本、第 25 体節で 67 本。第 7 体節で 85 本、第 20 体節で 77 本。第一背孔は第 12/13 体節 (原記載; Shen & Yeo, 2005)。

　環帯は第 14-16 体節を占める。雌性孔は第 14 体節の腹側中央に 1 個。雄性孔は第 18 体節にあり、しばしば突出する。雄性孔の直径は 0.5 mm (Shen & Yeo, 2005)。雄性孔間隔は体周の 0.29 倍 (Shen & Yeo, 2005)。雄性孔間剛毛は 14-17 本 (17 [原記載]、14 [Shen & Yeo, 2005])。性徴を欠くが、第 19 体節第一の二次環節の雄性孔と同一ライン上に小さな目立たない白色の斑を持つ (Shen & Yeo, 2005)。ただし、Shen & Yeo (2005) もこれは性徴ではないとしている。受精囊孔は第 7/8 体節間溝。受精囊孔間隔は、体周の 0.34倍 (Shen & Yeo, 2005)。

＜内部形態＞

　隔膜は第 5/6/7 体節間 (原記載) または第 5/6/7/8 体節間 (Shen & Yeo, 2005) や第 10/11/12 体節間 (原記載)、12/13/14 体節間 (Shen & Yeo, 2005) ではかなり厚く、第 8/9/10 体節間 (原記載) または 9/10 体節間 (Shen & Yeo, 2005) では欠く。8/9 体節間では膜状 (Shen & Yeo, 2005)。

　砂嚢は第 9-10 体節 (Shen & Yeo, 2005)。腸管は第 14 体節から膨大する (Shen & Yeo, 2005)。腸盲嚢を欠く。

　心臓は第 11-12 体節 (Shen & Yeo, 2005)。小型腎管 (Meronephridia) が第 6/7 体節間隔膜より前で藪状に生える (Shen & Yeo, 2005)。

　精巣は第 10-12 体節 (原記載; 貯精嚢を含んでいる？; 南谷, 私見) もしくは第 10-11 体節 (Shen & Yeo, 2005)。貯精嚢は第 11-12 体節 (Shen & Yeo, 2005)。摂護腺はかなり小さく、第 18 体節に限定される。摂護腺は、筋肉質の導管を持ち、輪状 (Shen & Yeo, 2005)。受精囊は第 7 体節に 1 対で、とても小さく、主嚢は球状。やや皺がかる (Shen & Yeo, 2005)。主嚢の長さは 1.2 mm で、嚢状部と導管部は同長 (Shen & Yeo, 2005)。小さな副嚢があり、導管はねじれている (Shen & Yeo, 2005)。生殖腺を欠く (Shen & Yeo, 2005)。

＜原記載（クリックして展開）＞

　Perichaeta taprobanae is a stout worm, measuring about 80-100 mm; the largest specimen was 105 mm in length; an individual measuring 84 millims. in length had a breadth of 6.5 mm and was composed of about 114 segments.

　The worm undoubtedly belongs to the restricted genus Perichaeta, although, as will be seen presently, one of the distinctive characters of the genus is absent: the setae from continuous rows and are numerous; on the first setigerous segment of one specimen I counted 52 setae, on the fifth 81, on the twelfth segment of the same individual there were 74, on the twenty-fifth 67. The setae formula is therefore as follows: segment I/ 52, V/ 81, XII/ 74, XXV/ 67. The setae are present on all the clitellar segments and form complete circles. Their form is not different from that of the setae elsewhere. Those upon the hinder segment of the body are nearly twice as long as those upon the anterior.

　The clitellum is composed of the usual three segments, but is a little indistinct at both ends.

　The oviducal pore is single and median; it lies in front of the circle of setae of segment XIV.

　The atrial pores are upon the XVIIIth segment and are sometimes very prominent- forming conical elevations- owing to a protrusion of a part of the atrium; the setae are interrupted for a short space on either side of each pore, which, however, lie directly in the line of the setae. I counted seventeen setae between the male pores.

　I could find no genital or copulatory papillae of any kind.

　The spermathecal pores were very evident in all the specimens; they lie between segments VII/VIII.

　The dorsal pores commence between segments XII/XIII.

　The anterior segments of the body are bi-or tri-annulate.

　With regard to the internal anatomy of the species, I only direct attention to those points which are known to be of importance in the discrimination of species. The position of the gizzard is perfectly normal; it lies in segments VIII-X, and the septa between these segments have nearly entirely disappeared, being represented only by a few ligaments binding the gizzard to the parietes. The intestine is very remarkable on account of the fact that there are no caeca. I looked for these structures very carefully, and entirely failed to discover them; they are always (according to my experience) quite easy to find when present. I must therefore conclude that the present species is unique in the absence of caeca. Although there appears to be no Earthworm known on other grounds referable to the genus Perichaeta (s. s.) which possesses no intestinal caeca, Mr. Fletcher has described a Megascolex in which caeca are present. In Perichaeta queenslandica, a worm with "interrupted circles of setae", there are a pair of lateral caeca arising from the intestine in segment XXV and directed anteriorly, as in all true Perichaeta with the exception of Perichaeta taprobanae; these two species evidently render it impossible to define strictly the genera Perichaeta and Megascolex, though as a matter of convenience those names may be, for the present at least, retained until more exceptions are made known. In other particulars the alimentary tract of this Earthworm does not diverge from the normal.

　The intersegmental septa commence to be distinct after the fourth segment; the first four septa, viz. those bounding segments V-VII, are rather thickened; as are also the first two septa which lie behind the gizzard, that is to say those which separate segments X/XI and XI/XII. The thick septa in front of the gizzard are covered with very conspicuous nephridial tufts.

　The sperm-sacs lie in segments X, XI and XII.

　The atria consist as usual of a thick muscular duct bent upon itself and of a glandular portion consisting of ramifying caeca; the latter is fairly compact except where it is cleft at its junction with the non-glandular part. The glandular part is much smaller than is usual in this genus, and is entirely limited to the XVIIIth segment. The muscular duct is unprovided with a dilated sac at its extremity.

　There is only a single pair of spermathecae, which lie in segment VIII. They also are small; and, as the facts contained in this account are based upon the dissection of several examples, I may emphasize the smallness of the atria and the spermathecae as a characteristic of the species. Each spermatheca consists of a globular portion communicating with the exterior by a narrow duct, to which is appended a small diverticulum consisting also of a swollen terminal portion and of a narrow duct.

Polypheretima taprobanae の形態 (Nguyen et al., 2014, p. 117, fig. 5 より)

分布

　国外ではインド (Aiyer, 1929; Gates, 1937a; Sawar et al., 2006)、スリランカ (Beddard, 1892; Stephenson, 1923)、ベトナム (Nguyen et al., 2014)、オーストラリア (Easton, 1982)、ハワイ (Reynolds, 2015v)、アルゼンチン (Mischis & Herrera, 2006) に分布する。

要検討：セーシェル、ブラジル、ハワイ、マダガスカル、フィジー、東南アジア、パプアニューギニア

生態

　Gates (1960c) は、本種を単為生殖が疑われる種としている。

シノニムリスト

Perichaeta taprobanae Beddard, 1892: 163.

Perichaeta taprobanae Beddard, 1895: 411.

Amyntas taprobanae (syn. pauli) Beddard, 1900: 648.

Pheretima taprobanae Michaelsen, 1900: 308.

Pheretima taprobanae pauli Michaelsen, 1900: 309.

Pheretima taprobanae Stephenson, 1923: 312.

Pheretima taprobanae Aiyer, 1929: 72.

Pheretima taprobanae Gates, 1937a: 209.

Pheretima taprobanae Gates, 1960c: 278. [記述のみ]

Pheretima taprobanae Gates, 1976c: 2. [記述のみ] (Apr, 1976)

Polypheretima taprobanae Easton, 1982: 734. [同定形質のみ]

Polypheretima taprobanae Shen & Yeo, 2005: 27 (syn. pauli). [形態記載] (Jun 29, 2005)

Metapheretima taprobanae Mischis & Herrera, 2006: 287.

Pheretima taprobanae Sawar et al., 2006: 4.

Polypheretima taprobanae Nguyen et al., 2014: 117 (syn. pauli). [記述のみ]

Polypheretima taprobanae Reynolds, 2015v: 119. [記述のみ] (Dec, 2015)

[要検討]

P. pauli Michaelsen, 1897: 243, 1900: 309

P. taprobanae Michaelsen, 1899: 140.

Easton, 1979, 1984

Gates, 1972: 220; Do, 1994; Nguyen, 1994; Pham, 1995a; Huynh, 1996; Nguyen & Tran, 2008

引用文献

Aiyer, K.S.P., 1929. An account of the oligochaeta of Travancore. Records of Indian Museum 31(1): 13-76.

Beddard, F. E., 1892. On some species of the genus Perichaeta (sensu stricto). Proceedings of the Zoological Society 1892: 153-172.

Beddard, F.E., 1895. A Monograph of the order of Oligochaeta. Oxford at the Clarendon Press. pp. 769.

Beddard, F.E., 1900. A revision of the earthworms of the genus Amyntas (Perichaeta). Proceedings of the Zoological Society of London 69(4): 609-652.

Easton, E.G., 1982. Australian pheretimoid earthworms (Megascolecidae: Oligochaeta): A synopsis with the description of a new genus and five new species. Australian Journal of Zoology 30: 711-735.

Gates, G.E., 1937c. Indian earthworms. I. The genus Pheretima. Records of the Indian Museum 39: 175-212.

Gates, G.E., 1960c. On Burmese earthworms of the family Megascolecidae. Bulletin of the Museum of Comparative Zoology123: 203-282.

Gates, G.E., 1976c. More on oligochaete distribution in North America. Megadrilogica 2(11): 1-6.

Michaelsen, W., 1900. Oligochaeta. Das Tierrich 10: 1-575.

de Mischis, C.C., Herrera, J.A.D., 2006. Review of the distribution of exotic earthworms (Annelida, Oligochaeta) in Argentina and confirmed examples of their introduction. Carribean Journal of Science 42(3): 285-293.

Nguyen, T.T., Tran, B.T.T., Nguyen, A.D., 2014. Earthworms of the 'acaecate' Pheretima group in Vietnam (Oligochaeta: Megascolecidae), with description of a new species from the Mekong delta. Zootaxa 3866(1): 105-121.

Reynolds, J.W., 2015v. A checklist by counties of earthworms (Oligochaeta: Acanthodrilidae, Glossoscolecidae, Lumbricidae, Megascolecidae, Ocnerodrilidae, Octochaetidae) in Hawaii, USA. Megadrilogica 19: 123-145.

Sarwar, M., Nadeem, A., Iqbal, M. K., Shafiq, T., 2006. Biodiversity of earthworm species relative to different flora. Punjab Univ. J. Zool. 21(1/2): 1-7.

Shen, H.P., Yeo, D.C.J., 2005. Terrestrial earthworms (Oligochaeta) from Singapore. The Raffles Bulletin of Zoology 53(1): 13-33.

Stephenson, J., 1923. The Fauna of British India, including Ceylon and Burma. Oligochaeta. Taylor & Francis, London. 518 pp.