习惯于夜行生活的蝙蝠，其敏锐的听觉和准确的回声定位能力令人惊讶，其视觉能力会因其夜行生活而导致退化吗？对此，由华东师范大学生命科学学院分子生态与进化实验室张树义教授与英国、爱尔兰学者联合课题组，大胆挑战“弱光环境促使动物视觉退化”的传统经典理论，提出了“感觉代偿”的感官进化新机制，揭示了蝙蝠的视觉世界。该研究成果5月26日在美国国家科学院院刊（PNAS）上在线发表。
蝙蝠精准的回声定位能力是哺乳动物界最发达的感觉形式之一。蝙蝠“家族”分为两支，一支是回声定位蝙蝠，主要以昆虫为食，眼睛微小；另一支是非回声定位蝙蝠，眼睛较大，以果实为食，被称为“旧大陆果蝠”。回声定位蝙蝠又分为“调频蝙蝠”和“恒频蝙蝠”两类。
课题组研究发现，虽然蝙蝠的夜行生活历史长达至少5200万年，但大部分蝙蝠仍然与多数哺乳动物一样具有“双色觉”，可以相应地看到紫外光和红光。而且非回声定位蝙蝠（旧大陆果蝠）和回声定位蝙蝠在色觉能力上并没有明显差异。
课题组首次提供了基因表达的数据，开发出一种重建祖先终止密码子的算法，并基于这种新的研究方法，对部分蝙蝠视觉退化的原因做出解释：旧大陆果蝠原本生活在树上，进化过程中有小部分栖息地变为基本无光的洞穴，长此以往导致这部分旧大陆果蝠视觉发生退化。但对恒频蝙蝠而言，视觉退化的根本原因在于它具有一种更发达的回声定位能力。发达的听觉使恒频蝙蝠不再需要发达的视觉，进而引起视觉退化。为适应生存环境，一种感觉形式的退化也会引起其他感觉形式的代偿性增强。这就如同盲人在丧失了视觉能力之后，触觉、听觉等其他感觉能力会有所增强。感觉代偿进化机制的提出，对于动物感觉系统的进化和夜行生活的研究具有重要的指导意义。（生物谷Bioon.com）
生物谷推荐原始出处：
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.
