Deep sea is a harsh environment characterized by high hydrostatic pressure and low temperatures. For instance, high hydrostatic pressure can disrupt actin organization and microtubules assembly, which have adverse influences on intracellular movements and cell motility. Nucleic acids structures can be influenced by not only high hydrostatic pressure but also cold temperatures. These unfavourable effects caused by the high hydrostatic pressure and coldness are challenging for deep-sea animals. In addition, there are chemosynthetic ecosystems, such as hydrothermal vents and hydrocarbon seeps, in the deep sea. Dense communities of megafauna rely on the nutrients produced by chemotrophic bacteria that are capable of utilizing chemical substances as energy resources. To study the po...[ Read more ]

Deep sea is a harsh environment characterized by high hydrostatic pressure and low temperatures. For instance, high hydrostatic pressure can disrupt actin organization and microtubules assembly, which have adverse influences on intracellular movements and cell motility. Nucleic acids structures can be influenced by not only high hydrostatic pressure but also cold temperatures. These unfavourable effects caused by the high hydrostatic pressure and coldness are challenging for deep-sea animals. In addition, there are chemosynthetic ecosystems, such as hydrothermal vents and hydrocarbon seeps, in the deep sea. Dense communities of megafauna rely on the nutrients produced by chemotrophic bacteria that are capable of utilizing chemical substances as energy resources. To study the potential mechanisms of biological adaptation to deep-sea environment, we performed genomic analysis of representative species from both deep-sea non-vent environment and deep-sea chemosynthetic environment, including Hirondellea gigas amphipod from Challenger Deep in Mariana Trench, Aldrovandia affinis fish from the Pacific Ocean, Phreagena okutanii clam from a deep-sea hydrothermal vent, Archivesica marissinica clam from a deep-sea methane seep, and Gigantopelta aegis gastropod from a hydrothermal vent. Our results suggest that genetic adaptation to the deep-sea environment are mediated by both gene family expansion and amino acid substitutions. Furthermore, the vent-endemic megafauna is highly dependent on the mutualistic relationships with their symbionts. The host provide intermediates to fulfill the metabolic needs of their endosymbionts, and in return, the symbionts are active to generate nutrients and provide to the hosts through lysis processes. Overall, my thesis study not only provides high-quality transcriptomes and genomes of a few representative deep-sea animals for future deep-sea studies but also facilitates a better understanding of the molecular adaptation to the deep sea.