海洋哺乳动物因其适应与陆地截然不同的海洋环境，具有重要的进化意义。但到目前为止，关于它们在海洋环境中生存的遗传基础方面的研究非常有限。

长须鲸

中国科学院昆明动物研究所张亚平院士、云南大学于黎研究员和博士研究生靳伟通过对海洋哺乳动物和陆地哺乳动物的犁鼻器系统特异表达基因——瞬时受体电位基因（TRPC2）的研究，为哺乳动物从陆地到海洋转变过程中的信息素感知方面的进化提供了重要信息。信息素在哺乳动物生殖和社会行为方面起重要作用，主要由犁鼻器系统感知。

该研究显示，完全适应于海洋生活的鲸目（长须鲸）的TRPC2基因是假基因，选择压力明显放松，基因功能丧失，而营半水生生活的加利福尼亚海狮的TRPC2基因是功能基因，仍然受到较强的选择压力。因此推测，鲸类因其完全适应于海洋生活，退化的犁鼻器信息素感知功能促使TRPC2基因假基因化，而对于“两栖”的加利福尼亚海狮来说，陆地生活仍然需要犁鼻器信息素感知，因此其TRPC2基因仍然是功能基因。进一步分析表明，犁鼻器信息素信号传导通路可能在鲸目的共同祖先时（32-53百万年之间）就已失去功能。令人惊奇的是，与加利福尼亚海狮不同，同样营半水生生活的港海豹和欧亚水獭的TRPC2基因都是假基因。TRPC2基因很有可能在港海豹和欧亚水獭中独立假基因化和丧失功能（分别大约在2.7百万年和1.8百万年后）。其它未知的选择压力或感觉器官补偿机制可能促使了港海豹和欧亚水獭的TRPC2基因假基因化。

原始出处：

Molecular Biology and Evolution, doi:10.1093/molbev/msq027

Characterization of TRPC2, an essential genetic component of VNS chemoreception provides insights into the evolution of pheromonal olfaction in secondary-adapted marine mammals

Li Yu*,$, Wei Jin*,,$, Jia-xin Wang*, Xin Zhang*, Meng-meng Chen, Zhou-hai Zhu*, Hang Lee&, Muyeong Lee& and Ya-ping Zhang*,

* Laboratory for Conservation and Utilization of Bio-resource & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, 650091, PR, China
State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
The school of life science, Yunnan University, Kunming, 650200, China
& Conservation Genome Resource Bank for Korean Wildlife, Research Institute for Veterinary Science and Coll. of Vet. Med., Seoul National Univ., Seoul 151-742, South Korea

Pheromones are chemical cues released and sensed by individuals of the same species, which are of major importance in regulating reproductive and social behaviors of mammals. Generally, they are detected by the vomeronasal system (VNS). Here, we first investigated and compared an essential genetic component of vomeronasal chemoreception, i.e., TRPC2 gene, of four marine mammals varying the degree of aquatic specialization and related terrestrial species in order to provide insights into the evolution of pheromonal olfaction in the mammalian transition from land to water. Our results based on sequence characterizations and evolutionary analyses, for the first time, show the evidence for the ancestral impairment of vomeronasal pheromone signal transduction pathway in fully-aquatic cetaceans, supporting a reduced or absent dependence on olfaction as a result of the complete adaptation to the marine habitat, while the amphibious California sea lion was found to have a putatively functional TRPC2 gene, which is still under strong selective pressures, reflecting the reliance of terrestrial environment on chemical recognition among the semi-adapted marine mammals. Interestingly, our study found that, unlike that of the California sea lion, TRPC2 genes of the harbor seal and the river otter, both of which are also semi-aquatic, are pseudogenes. Our data suggests that other unknown selective pressures or sensory modalities might have promoted the independent absence of a functional VNS in these two species. In this respect, the evolution of pheromonal olfaction in marine mammals appears to be more complex and confusing than has been previously thought. Our study makes a useful contribution to the current understanding of the evolution of pheromone perception of mammals in response to selective pressures from an aquatic environment.