华盛顿湖1957年和2006年出产的不同年份的棘鱼的比较
生物谷报道：5月20日出版的《当代生物学》刊登了一篇棘鱼退化的研究报告。美国西雅图附近华盛顿湖的污染随着时间渐渐消退时，一种名为棘鱼的多刺小鱼可能出现了倒退进化，重新长出远古“装甲”。
20世纪50年代，美国华盛顿州太平洋海岸的内陆湖――华盛顿湖遭受严重的磷污染，大约10年后成了一个121400公顷的污水池。之后，美国花1.4亿美元高价来清理此湖，使其变成了如今的游乐天堂。然而这一恢复让此湖中的棘鱼出现了退化，科学家分析其原因是湖中的捕食者如鲑鱼的威胁促使此鱼重新进化成了旧时的模样，长出了防御用的装甲板。
当华盛顿湖遭受严重的磷污染时，能见度大约只有76厘米，棘鱼根本不需装甲来保护，因为躲在污泥中就能逃过捕食者的视线。1968年，此湖清理完毕之后，能见度达到了3米，如今的能见度则有7.6米。
科学家发现，在清理之前，只有6%的棘鱼有完整的装甲，如今有49%的棘鱼全身披满装甲了，用骨质板从头到尾保护自己。另有35%的棘鱼有部分装甲，其一半的身体被保护着。该研究小组表示，这一戏剧性的快速适应是一种倒退进化的事例，因为棘鱼本来是越来越进化成没有装甲的。（生物谷www.bioon.com）
生物谷推荐原始出处：
Current Biology，Vol 18, 769-774，Jun Kitano，Catherine L. Peichel
Reverse Evolution of Armor Plates in the Threespine Stickleback
Jun Kitano,1 Daniel I. Bolnick,2 David A. Beauchamp,3 Michael M. Mazur,3 Seiichi Mori,4 Takanori Nakano,5 and Catherine L. Peichel1,
1 Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109
2 Section of Integrative Biology, University of Texas, Austin, Texas 78712
3 U.S. Geological Survey, Washington Cooperative Fish & Wildlife Research Unit, School of Aquatic and Fisheries Sciences, University of Washington, Seattle, Washington 98105
4 Biological Laboratory, Gifu-keizai University, Ogaki, Gifu 503-8550, Japan
5 Research Department, Research Institute for Humanity and Nature, 335 Takashima-cho, Kamigyo-ku, Kyoto 602-0878, Japan
Corresponding author
Catherine L. Peichel
cpeichel@fhcrc.org
Faced with sudden environmental changes, animals must either adapt to novel environments or go extinct. Thus, study of the mechanisms underlying rapid adaptation is crucial not only for the understanding of natural evolutionary processes but also for the understanding of human-induced evolutionary change, which is an increasingly important problem [1, 2, 3, 4, 5, 6, 7, 8]. In the present study, we demonstrate that the frequency of completely plated threespine stickleback fish (Gasterosteus aculeatus) has increased in an urban freshwater lake (Lake Washington, Seattle, Washington) within the last 40 years. This is a dramatic example of “reverse evolution,” [9] because the general evolutionary trajectory is toward armor-plate reduction in freshwater sticklebacks [10]. On the basis of our genetic studies and simulations, we propose that the most likely cause of reverse evolution is increased selection for the completely plated morph, which we suggest could result from higher levels of trout predation after a sudden increase in water transparency during the early 1970s. Rapid evolution was facilitated by the existence of standing allelic variation in Ectodysplasin (Eda), the gene that underlies the major plate-morph locus [11]. The Lake Washington stickleback thus provides a novel example of reverse evolution, which is probably caused by a change in allele frequency at the major plate locus in response to a changing predation regime.
