New progress has been made in the research on adaptive evolution and conservation of sea dragon species

Recently, Lin Qiang, a researcher at the South China Sea Institute of Oceanology, Chinese Academy of Sciences, and Gao Zexia, a professor at Huazhong Agricultural University, analyzed the evolutionary characteristics and genetic basis of the special mimicry formation of Ye Hailong, elucidated the molecular regulation mechanism of its complex trait formation based on gene editing technology, and predicted the evolution trend of suitable habitat range for sea dragon species under future climate change. The research was published as a cover paper in Science China – Life Sciences.

Cover of the current issue. Photo courtesy of the research team

Leafy sea dragons live off the southern coast of Australia and are covered with leaf-like appendages that blend perfectly into the seagrass beds they inhabit. Similar to other sea dragon species, the leaf sea dragon population is facing an unprecedented crisis due to habitat destruction, environmental pollution, human activities and other factors. However, the current research on leaf sea dragons is very limited, how do they adapt to the special habitat of seagrass beds? How will their suitable habitat change under future climate change? There is no answer yet.

Previously, Lin Qiang’s team conducted a series of studies on the evolution of complex traits of sea dragon species, and successively analyzed the genetic basis of traits such as loss of ventral fins, spines, tooth loss, and spleen loss in sea dragons. In the latest study, Lin Qiang’s team conducted a comparative genomics analysis of Ye Hailong and found that the Ye Hailong genome has a higher evolutionary rate compared to other fish.

The research team further excavated the relevant genes and found that multiple rapidly evolving and positive selection genes were involved in the developmental pathways related to leaf tissues such as bone and collagen, which may be the potential reason for the highly specialized phenotype of leaf sea dragons. Zebrafish knockout experiments on one of the key genes, bmp6, using CRISPR-Cas9 gene editing technology, showed that the development of mutant intermuscular spurs was significantly affected, indicating the important role of this gene in bone development.

Previous research by the team has shown significant shrinkage in the family of chemoreceptors in sea dragon fish, while the leaf sea dragon has lost more than other sea dragon species, with the lowest number of OR and V1R olfactory receptors among reported teleost fishes. Studies have shown that the amount of OR in fish is significantly correlated with habitat complexity. Leaf sea dragon inhabits seagrass bed ecosystem and is highly dependent on specific habitats, coupled with the characteristics of single diet, poor swimming and migratory characteristics, it is speculated that the loss of its olfactory receptors is related to its adaptation to unique habitats.

It is understood that the research results published in Science Frontiers by Lin Qiang’s team have successfully analyzed the evolutionary characteristics and sex determination mechanism of the complex traits of the grass sea dragon, and the two sister studies have laid the foundation for the study of the formation and evolution mechanism of such special species, and provided an important scientific basis for the scientific protection of key species of sea dragons.

Lin Qiang, the corresponding author of the paper, said that in the long-term evolutionary process, the highly specialized phenotype and lifestyle of the leaf sea dragon and grass sea dragon make it perfectly adapted to the special seagrass bed ecosystem. However, in recent years, the combined influence of climate change and human activities has severely damaged the suitable habitat of sea dragons. Using species distribution models for predictions, the results show that the suitable habitat range of the regionally endemic species leaf sea dragon and grass sea dragon will be significantly reduced by the end of this century compared with widespread species such as the linear seahorse, and the existing habitat area may no longer be suitable for its survival in the future. In addition, the dispersal capacity of sea dragons is extremely weak, making it difficult to migrate long distances into new suitable environments. Therefore, conservation strategies for sea dragons need to be developed not only for their species, but also for future climate change and habitat types. (Source: China Science News, Zhu Hanbin, Qu Hui)

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