生物谷報(bào)道：魚類皮膚發(fā)出的明亮的金屬光澤往往是養(yǎng)魚的人的一個(gè)樂(lè)趣之源。現(xiàn)在,，來(lái)自以色列的研究人員解開(kāi)了魚類金屬光澤之謎,。這種光澤市由于一種復(fù)雜的晶體系統(tǒng)能夠增強(qiáng)反光，并且?guī)椭~類在自然環(huán)境中躲避捕食者的追捕,。這項(xiàng)研究的結(jié)果刊登在新一期的Crystal Growth & Desigh雜志上,。
在這項(xiàng)新研究中，Lia Addadi和同事指出,，研究人員在多年前已經(jīng)知道魚類皮膚中的鳥嘌呤晶體反射光線,，從而產(chǎn)生了金屬光澤。
這種銀色的光反射是一種偽裝,，有助于保護(hù)魚在游近水表面時(shí)躲避捕食者,。但是，這些鳥嘌呤晶體的確切形狀以及它們?nèi)绾喂ぷ魅匀皇且粋€(gè)謎。
研究人員從日本Koi魚的皮膚中抽提出鳥嘌呤晶體,，并利用X射線衍射和電子顯微鏡對(duì)晶體進(jìn)行了分析,。
他們發(fā)現(xiàn)，這種生物制造的晶體與一種與實(shí)驗(yàn)室制造的晶體所不同的意外方向形成,，并且他們獨(dú)特的形狀能夠提高對(duì)光的反射力,。這種晶體的排列方式是魚類的一種進(jìn)化策略，以使它們能夠制造出更有效的光子晶體,。
生物谷推薦原始出處：
ASAP Cryst. Growth Des., ASAP Article, 10.1021/cg0704753
Web Release Date: January 5, 2008
Copyright © 2008 American Chemical Society
Biogenic Guanine Crystals from the Skin of Fish May Be Designed to Enhance Light Reflectance
Avital Levy-Lior,‡ Boaz Pokroy,† Berta Levavi-Sivan,‡ Leslie Leiserowitz,‡ Steve Weiner,‡ and Lia Addadi‡*
Departments of Structural Biology and Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel, and the Department of Materials Engineering, Technion, Haifa, 32000, Israel, and the Department of Animal Sciences, Faculty of Agriculture, Hebrew University, Rehovot 76100, Israel
Received May 24, 2007
Revised October 14, 2007
Abstract
The metallic luster from the skin of fish is due to a photonic crystal system composed of multilayer stacks of cytoplasm and crystals. The crystals are described as thin (50−100 nm) plates of guanine, with no reference to their hydration state. We established through X-ray diffraction that their crystal structure is that of anhydrous guanine. We noted that their crystal structure-function relationship is exceptional compared to other purines with similar molecular stacking of the crystal structure. These elongate in the direction of molecular stacking, in contrast to the biogenic anhydrous guanine crystals whose smallest dimension is in the stacking direction. On the basis of the known crystal structure of anhydrous guanine, theoretical growth morphology was calculated. These calculations predict crystals elongated in the direction of the molecular stacking. The exposed molecular plane of the biogenic crystals is the (102) plane, which is composed of densely packed H-bonded guanine molecules. It is known that the in-plane polarizability of guanine molecules is significantly higher than the direction perpendicular to the molecular plane, most likely causing anisotropy of the crystals refractive index. It is therefore conceivable that the unique morphology observed in crystals from the skin of fish is designed to enhance their light reflective properties.
相關(guān)新聞：
誘拐雌性的雄魚基因被發(fā)現(xiàn)
在新一期的BMC Biology雜志上發(fā)表的一項(xiàng)研究顯示，雄性鯛魚（cichlid fish）的一種基因進(jìn)化出了引誘雌魚以使雄魚能將精子儲(chǔ)存在雌魚嘴里的特殊功能,。
這項(xiàng)研究揭示出,，這個(gè)基因與鯛魚魚鰭上的類卵標(biāo)記有關(guān)。研究還揭示出了這些標(biāo)記的進(jìn)化歷史,，而這種標(biāo)記則是這種魚怪異的口交成功的核心,。
德國(guó)Konstanz大學(xué)的研究人員飼養(yǎng)了19種鯛魚，并且鑒定出一種與在魚鰭的橢圓斑點(diǎn)中產(chǎn)生黃色細(xì)胞的基因,。這些被稱為卵模擬物的標(biāo)記存在于雄魚的臀鰭上,。這種魚是所謂的母親口育魚（在口腔中繁育幼仔的魚）。一旦雌魚生出魚卵,，它就會(huì)將卵放進(jìn)它的嘴巴里,。雌魚會(huì)被雄魚魚鰭上的類似卵的標(biāo)記所吸引，然后雌魚就會(huì)接近雄魚,。當(dāng)雌魚類靠近雄魚的臀鰭時(shí),，雄魚類會(huì)將精子排到雌魚口中，進(jìn)而受精卵子,。
鯛魚是一類包括羅非魚和天使魚的魚屬,。在東非大約有1800多種鯛魚，并且其中80％屬于麗魚類（haplochromines）,，其特征就是有類似卵的圖案,。
這種與產(chǎn)生能模擬卵的色斑有關(guān)的基因叫做colony-stimulating factor 1 receptor a (csf1ra)。研究人員還證實(shí),，這種基因在一種親緣關(guān)系較遠(yuǎn)的種的模擬卵中也發(fā)生了表達(dá),，而在這種魚中的色斑不是出現(xiàn)在臀鰭而是在胸鰭位置。
這兩種獨(dú)立的模擬卵能夠作為檢測(cè)相同的基因途徑是否與模擬形態(tài)類型有關(guān)的一種模型系統(tǒng),。
