Mudskipper genomes provide insights into the terrestrial adaptation of amphibious fishes

Xinxin You, Chao Bian, Qijie Zan, Xun Xu, Xin Liu, Jieming Chen, Jintu Wang, Ying Qiu, Wujiao Li, Xinhui Zhang, Ying Sun, Shixi Chen, Wanshu Hong, Yuxiang Li, Shifeng Cheng, Guangyi Fan, Chengcheng Shi, Jie Liang, Y. Tom Tang, Chengye Yang, Zhiqiang Ruan, Jie Bai, Chao Peng, Qian Mu, Jun Lu, Mingjun Fan, Shuang Yang, Zhiyong Huang, Xuanting Jiang, Xiaodong Fang, Guojie Zhang, Yong Zhang, Gianluca Polgar, Hui Yu, Jia Li, Zhongjian Liu, Guoqiang Zhang, Vydianathan Ravi, Steven L. Coon, Jian Wang, Huanming Yang, Byrappa Venkatesh, Jun Wang, Qiong Shi

Mudskippers are amphibious fishes that have developed morphological and physiological adaptations to match their unique lifestyles. Here we perform whole-genome sequencing of four representative mudskippers to elucidate the molecular mechanisms underlying these adaptations. We discover an expansion of innate immune system genes in the mudskippers that may provide defence against terrestrial pathogens. Several genes of the ammonia excretion pathway in the gills have experienced positive selection, suggesting their important roles in mudskippers' tolerance to environmental ammonia. Some vision-related genes are differentially lost or mutated, illustrating genomic changes associated with aerial vision. Transcriptomic analyses of mudskippers exposed to air highlight regulatory pathways that are up- or down-regulated in response to hypoxia. The present study provides a valuable resource for understanding the molecular mechanisms underlying water-to-land transition of vertebrates.