生物谷：英國(guó)牛津大學(xué)的科學(xué)家在7月6日出版的《科學(xué)》雜志上發(fā)表論文稱,，他們發(fā)現(xiàn)一種罕見(jiàn)的無(wú)內(nèi)臟蠕蟲(chóng)并不能從外表判斷歸屬,，它與?？八复嬖谥^近的親緣關(guān)系,。這一發(fā)現(xiàn)有望改變?nèi)藗儗?duì)進(jìn)化過(guò)程的傳統(tǒng)認(rèn)識(shí),。
這種蠕蟲(chóng)名為Buddenbrockia,，自1851年首次被發(fā)現(xiàn)以來(lái),，科學(xué)家只有為數(shù)不多的幾次得以瞻仰它的“尊容”。該蠕蟲(chóng)無(wú)口,、無(wú)內(nèi)臟,、無(wú)大腦、無(wú)神經(jīng)脊索,，身體結(jié)構(gòu)無(wú)上下,、左右、前后之分,，呈完全的對(duì)稱形狀,，故而關(guān)于它在動(dòng)物王國(guó)里的“地位”問(wèn)題，一直困擾著科學(xué)家,。
為了弄清該種蠕蟲(chóng)的歸屬問(wèn)題,，此次研究的領(lǐng)導(dǎo)者,、牛津大學(xué)教授Peter Holland及同事分析了Buddenbrockia的50種基因，并與其它動(dòng)物的基因作了比較,。他們發(fā)現(xiàn),，雖然長(zhǎng)得像蠕蟲(chóng)，但是Buddenbrockia卻與?？八傅葎?dòng)物有著更近的親緣關(guān)系,。Holland教授說(shuō)：“這說(shuō)明Buddenbrockia類蠕蟲(chóng)的身體形狀是由兩種完全不同的動(dòng)物經(jīng)過(guò)至少兩次的進(jìn)化而來(lái)。這是已發(fā)現(xiàn)的最令人驚訝的‘趨同進(jìn)化’（convergent evolution）的例子,，因?yàn)檫@不是個(gè)體器官或身體某一部分的趨同進(jìn)化,，而是整個(gè)身體的趨同進(jìn)化。”
Buddenbrockia與可致鮭魚(yú)死亡的寄生蟲(chóng)Tetracapsula bryosalmonae有著緊密的親緣關(guān)系,，而Tetracapsula bryosalmonae因?yàn)槠銬NA很難從寄主DNA中分離使得科學(xué)家無(wú)從對(duì)其進(jìn)行研究?，F(xiàn)在則可以通過(guò)研究更容易分離得到的Buddenbrockia DNA來(lái)研究此類寄生蟲(chóng)的防治方法，這對(duì)于漁民來(lái)說(shuō)是個(gè)大好消息,。
針對(duì)此次研究的意義,，Holland教授表示，目前,，動(dòng)物更多地是根據(jù)外形的相似性而不是相互間基因的聯(lián)系被分類,，基因探測(cè)技術(shù)將有助于理清這些動(dòng)物間的親緣關(guān)系。（科學(xué)網(wǎng)）
原始出處:
Science 6 July 2007:
Vol. 317. no. 5834, pp. 116 - 118
DOI: 10.1126/science.1142024
Buddenbrockia Is a Cnidarian Worm
Eva Jiménez-Guri,1* Hervé Philippe,2* Beth Okamura,3,4 Peter W. H. Holland1
A major evolutionary divide occurs in the animal kingdom between the so-called radially symmetric animals, which includes the cnidarians, and the bilaterally symmetric animals, which includes all worm phyla. Buddenbrockia plumatellae is an active, muscular, parasitic worm that belongs to the phylum Myxozoa, a group of morphologically simplified microscopic endoparasites that has proved difficult to place phylogenetically. Phylogenetic analyses of multiple protein-coding genes demonstrate that Buddenbrockia is a cnidarian. This active muscular worm increases the known diversity in cnidarian body plans and demonstrates that a muscular, wormlike form can evolve in the absence of overt bilateral symmetry.
1 Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
2 Canadian Institute for Advanced Research, Centre Robert-Cedergren, Département de Biochimie, Université de Montréal, Succursale Centre-Ville, Montréal, Québec, Canada H3C3J7.
3 School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6BX, UK.
4 Department of Zoology, Natural History Museum, Cromwell Road, London SW7 5BD, UK.
* These authors contributed equally to this work.
To whom correspondence should be addressed. E-mail: [email protected]
