Muscle Fiber Distribution in Twin-Tail Goldfish: Evolutionary Insights
The twin-tail morphology of ornamental goldfish is a product of artificial selection. This unique structure does not exist in any other fish lineages, and remarkably, the twin-tail goldfish possess a distinct muscle structure found exclusively in their lineage. This suggests that an entirely novel muscle structure has emerged during the process of artificial selection. In this study, we conducted immunohistochemical analyses on this twin-tail-specific muscle structure. Our findings indicate that the distribution of slow muscle fibers follows pre-existing morphogenetic mechanisms, despite the extreme morphological divergence introduced by selective breeding. These results provide crucial insights into the relationship between selective pressures and inherent developmental mechanisms, shedding light on how newly emerged morphologies are shaped through a combination of evolutionary constraints and artificial selection.
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