International Journal of Aquaculture, 2025, Vol.15, No.5, 255-265 http://www.aquapublisher.com/index.php/ija 263 armored fishes (Gardner et al., 2019). Developmental biology and Evo-Devo compare the similarities and differences in embryonic development of existing biological species, especially gene expression, to give a glimpse into the mechanisms of ancient evolutionary events (Diogo, 2018). In addition to traditional molecular clocks, statistical methods can now integrate fossil and molecular data to build "synthetic evolutionary models". Total fossil incidence, species diversity curve, etc. can be placed in the Bayesian framework together with the molecular phylogenetic tree to infer the diversity rate of each branch. Such macroevolutionary models have been used in fish groups such as the Orozoite, identifying the rate of differentiation and possible drivers of their specific time in geological history (Sun and Mai, 2025). Although it is extremely difficult to extract DNA from fish fossils, there have been cases of successful extraction of ancient DNA for fish remains tens of thousands of years ago in the Holocene or Ice Age. Paleo DNA can directly reveal the genetic diversity and evolutionary dynamics of past fish populations. 8 Prospects and Conclusions Although fish evolution research has made great progress, there are still some limitations and unsolved mysteries in our understanding of its long history. The incompleteness of fossil record remains a major challenge. There is a relatively scarcity of fish fossils found in many critical periods or key areas, resulting in a "blank" in the evolutionary sequence. In terms of molecular phylogenetics, the contradiction between different data and methods still exists. Systematic trees constructed by different genes occasionally produce topological conflicts, or have insufficient resolution for some fast radiation nodes. This is particularly evident in higher-order phylogenetics (such as the ancient trunk relationship) and low-order fast-differentiated taxa (such as the internal relationship of cichlid radiation). Multidisciplinary data fusion itself also has bottlenecks. Data scales and properties vary in different fields, and combining them requires careful methodological design. For example, how to quantify and compare the relationship between developmental gene expression and fossil morphology, how to extrapolate modern ecological observations to geological time scales, etc., these need to be further explored. Fish evolution research also faces some new challenges. Global climate change and human activities are profoundly affecting contemporary fish diversity, and species distribution and evolutionary trajectories may be artificially altered. How to distinguish current changes from natural changes in geological periods and explore the potential impact of the Anthropocene on the future evolution of fish is an emerging topic. Some emerging technologies and methods are expected to break through the current bottleneck and inject new impetus into fish evolution research. Among them, what is worth looking forward to is the advancement of ancient DNA technology. At present, ancient DNA is mostly used in fish specimens since the ice age, but with the improvement of sequencing and extraction methods, it is not ruled out that DNA fragments can be obtained from older fossils. Another revolutionary field is comparative genomics and functional genomics. As thousands of fish genomes are sequenced, we will fully enter the era of big data, and we can compare the differences in the structure, number of genes, regulatory sequences and other differences in different fish genomes. At the same time, artificial intelligence and computing simulation will also play a greater role in this field. Machine learning can assist in analyzing a large number of fossil morphological pictures or three-dimensional models, extract classification characteristics from objective data, and judge environmental adaptation patterns. Studying the evolutionary path of fish is not only about tracing the history of a group itself, but also is of great significance to understanding the origin and adaptation mechanism of diversity in the entire vertebrate. Fish cover the first occurrence of many key evolutionary events in vertebrates: jaw, teeth, paired appendages, lung and swimmer bladder, inner nostrils, ovoviparity, etc. They all evolved first in fish and then improved and expanded in other vertebrates later. Therefore, the story of fish is actually the first half of our vertebrate evolution. Acknowledgements Thank you to all reviewers for their meticulous review, and also thank the members of the research team and technicians for their support in experimental design and data analysis.
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