A complete new sequence of the Yap hadal snail genome provides information on how the unusual fish survives in some of the deepest parts of the ocean. Xinhua Chen from Fujian Agriculture and Forestry University and Qiong Shi from BGI Academy of Marine Sciences published their analysis of the new genome on May 13 in the journal PLOS Genetics.
Animals living in deep sea environments face many challenges, including high pressures, low temperatures, little food, and almost no light. Fish are the only backbone animals that live in the hadal zone – defined as depths less than 6,000 meters – and hadal snails live in at least five separate sea trenches. Chen, Shi and their colleagues constructed a complete high-quality genomic sequence from the Yap hadal snail to understand how it adapted to life on the high seas. The fish were captured in the Yap pit in the Western Pacific Ocean at a depth of about 7,000 meters.
Analysis of the new genome revealed multiple adaptations for living in a cold, dark, high-pressure environment. The snail carries additional genes for DNA repair, which can help keep its genome intact under high pressures. It also has five copies of a gene for an enzyme that takes a compound produced by bacteria in its gut and turns it into one that stabilizes the structure of proteins under high hydrostatic pressure. The snail has also lost some genes involved in sight, taste, and smell, which are likely unnecessary in its dark, food-limited environment.
These new findings offer clues to the mechanisms by which snails evolved to survive in ocean trenches. However, the researchers stress that more studies will be needed to confirm the functions of these genetic changes. In addition, the high quality genomic sequence can serve as a resource for future in-depth investigations of snails and other animals living in the hadal zone.
Chen adds, “Many genes associated with DNA repair show evidence of positive selection and increased copy number in the Yap hadal snail genome, potentially reflecting the difficulty of maintaining the integrity of the snail. DNA under high hydrostatic pressure. The five copies of trimethylamine N- oxide-generating enzyme (TMAO), the flavin-containing monooxygenase-3 gene (fmo3) and the abundance of trimethylamine-generating bacteria (TMA) in the gut of the Yap hadal snail could provide enough TMAO to improve protein stability under hadal conditions. “
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