一項新的研究報告說,一個3500萬年前的企鵝的羽毛化石披露了某些現代特質的線索。 在現代鳥類的羽毛中所發現的被稱作黑色素體的色素顆粒在鳥羽化石中首次報導的時間是在2008年。
這些色素顆粒非常細小,人的毛髮直徑可容納一百個黑色素體。 如今,Julia Clarke及其同事證明,化石化的黑色素體可確定企鵝的演化發展。 企鵝高度適應其寒冷的水生環境。 它們的翅膀和羽毛的變化使得它們能夠快速地遊泳(水中「飛行」)並保護它們在近乎凍結的水中不受傷害;然而,解釋企鵝羽毛是如何演化的數據則非常少。 在本研究中,研究人員對一個在秘魯發現的羽毛得到完好保存的3500萬年前的企鵝進行了分析。 儘管遠古企鵝的翅膀和羽毛的外觀與當今企鵝的相似,但該研究團隊發現,其羽毛中的黑色素體則與當今企鵝的並不一樣。
明確地說,遠古企鵝的色素細胞與許多其它水鳥的色素細胞類似,但卻與當今企鵝的色素細胞不同。 這些結果提示,遠古企鵝羽毛的形狀和構成在影響諸如力量和水阻力等性質的微觀變化之前就已經演化了,這也許對解釋企鵝是如何及何時適應於水中生活的有所幫助。(生物谷Bioon.com)
生物谷推薦英文摘要:
Science DOI: 10.1126/science.1193604
Fossil Evidence for Evolution of the Shape and Color of Penguin Feathers
Julia A. Clarke,1,* Daniel T. Ksepka,2,3 Rodolfo Salas-Gismondi,4 Ali J. Altamirano,4 Matthew D. Shawkey,5 Liliana D』Alba,5 Jakob Vinther,6 Thomas J. DeVries,7 Patrice Baby8,9
Penguin feathers are highly modified in form and function, but there have been no fossils to inform their evolution. A giant penguin with feathers was recovered from the late Eocene (~36 million years ago) of Peru. The fossil reveals that key feathering features including undifferentiated primary wing feathers and broad body contour feather shafts evolved early in the penguin lineage. Analyses of fossilized color-imparting melanosomes reveal that their dimensions were similar to those of nonpenguin avian taxa and that the feathering may have been predominantly gray and reddish-brown. By contrast, the dark black-brown color of extant penguin feathers is generated by strikingly large, ellipsoidal melanosomes previously unknown for birds. The nanostructure of penguin feathers was thus modified after earlier macrostructural modifications of feather shape linked to aquatic flight.
1 Department of Geological Sciences, University of Texas at Austin, Austin, TX 78712, USA.
2 Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695–8208, USA.
3 Department of Paleontology, North Carolina Museum of Natural Sciences, Raleigh, NC 27601–1029, USA.
4 Departamento de Paleontología de Vertebrados, Museo de Historia Natural-UNMSM, Lima 14, Perú.
5 Integrated Bioscience Program, University of Akron, Akron, OH 44325, USA.
6 Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA.
7 Burke Museum of Natural History and Culture, University of Washington, Seattle, WA 98195, USA.
8 IRD; LMTG; 14 Av. Edouard Belin, F-31400 Toulouse, France.
9 Université de Toulouse; UPS; LMTG; F-31400 Toulouse, France.