習(xí)慣于夜行生活的蝙蝠，其敏銳的聽覺和準(zhǔn)確的回聲定位能力令人驚訝,，其視覺能力會因其夜行生活而導(dǎo)致退化嗎,？對此，由華東師范大學(xué)生命科學(xué)學(xué)院分子生態(tài)與進(jìn)化實(shí)驗(yàn)室張樹義教授與英國,、愛爾蘭學(xué)者聯(lián)合課題組,，大膽挑戰(zhàn)“弱光環(huán)境促使動(dòng)物視覺退化”的傳統(tǒng)經(jīng)典理論，提出了“感覺代償”的感官進(jìn)化新機(jī)制,，揭示了蝙蝠的視覺世界,。該研究成果5月26日在美國國家科學(xué)院院刊（PNAS）上在線發(fā)表。
蝙蝠精準(zhǔn)的回聲定位能力是哺乳動(dòng)物界最發(fā)達(dá)的感覺形式之一,。蝙蝠“家族”分為兩支,，一支是回聲定位蝙蝠，主要以昆蟲為食,，眼睛微?。涣硪恢欠腔芈暥ㄎ或?，眼睛較大,，以果實(shí)為食，被稱為“舊大陸果蝠”,?；芈暥ㄎ或鹩址譃?ldquo;調(diào)頻蝙蝠”和“恒頻蝙蝠”兩類,。
課題組研究發(fā)現(xiàn)，雖然蝙蝠的夜行生活歷史長達(dá)至少5200萬年,，但大部分蝙蝠仍然與多數(shù)哺乳動(dòng)物一樣具有“雙色覺”,，可以相應(yīng)地看到紫外光和紅光。而且非回聲定位蝙蝠（舊大陸果蝠）和回聲定位蝙蝠在色覺能力上并沒有明顯差異,。
課題組首次提供了基因表達(dá)的數(shù)據(jù),，開發(fā)出一種重建祖先終止密碼子的算法，并基于這種新的研究方法,，對部分蝙蝠視覺退化的原因做出解釋：舊大陸果蝠原本生活在樹上,，進(jìn)化過程中有小部分棲息地變?yōu)榛緹o光的洞穴，長此以往導(dǎo)致這部分舊大陸果蝠視覺發(fā)生退化,。但對恒頻蝙蝠而言,，視覺退化的根本原因在于它具有一種更發(fā)達(dá)的回聲定位能力。發(fā)達(dá)的聽覺使恒頻蝙蝠不再需要發(fā)達(dá)的視覺,，進(jìn)而引起視覺退化。為適應(yīng)生存環(huán)境,，一種感覺形式的退化也會引起其他感覺形式的代償性增強(qiáng),。這就如同盲人在喪失了視覺能力之后，觸覺,、聽覺等其他感覺能力會有所增強(qiáng),。感覺代償進(jìn)化機(jī)制的提出，對于動(dòng)物感覺系統(tǒng)的進(jìn)化和夜行生活的研究具有重要的指導(dǎo)意義,。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS May 26, 2009, doi: 10.1073/pnas.0813201106
The evolution of color vision in nocturnal mammals
Huabin Zhaoa,b, Stephen J. Rossiterc,1, Emma C. Teelingd,1, Chanjuan Lib, James A. Cottonc and Shuyi Zhangb,1
Nonfunctional visual genes are usually associated with species that inhabit poor light environments (aquatic/subterranean/nocturnal), and these genes are believed to have lost function through relaxed selection acting on the visual system. Indeed, the visual system is so adaptive that the reconstruction of intact ancestral opsin genes has been used to reject nocturnality in ancestral primates. To test these assertions, we examined the functionality of the short and medium- to long-wavelength opsin genes in a group of mammals that are supremely adapted to a nocturnal niche: the bats. We sequenced the visual cone opsin genes in 33 species of bat with diverse sensory ecologies and reconstructed their evolutionary history spanning 65 million years. We found that, whereas the long-wave opsin gene was conserved in all species, the short-wave opsin gene has undergone dramatic divergence among lineages. The occurrence of gene defects in the short-wave opsin gene leading to loss of function was found to directly coincide with the origin of high-duty-cycle echolocation and changes in roosting ecology in some lineages. Our findings indicate that both opsin genes have been under purifying selection in the majority bats despite a long history of nocturnality. However, when spectacular losses do occur, these result from an evolutionary sensory modality tradeoff, most likely driven by subtle shifts in ecological specialization rather than a nocturnal lifestyle. Our results suggest that UV color vision plays a considerably more important role in nocturnal mammalian sensory ecology than previously appreciated and highlight the caveat of inferring light environments from visual opsins and vice versa.
