Relationship between fish skin shrinkage and a fish’s physiological temperature according to movie analysis

Fish skin, which is primarily composed of collagen, shrinks at a certain temperature relating to the fish’s physiological temperature (Tp). Based on our previous reports, the denaturation temperature (Td) of type I collagen in fi sh species is correlated with Tp. In this study, we developed a simple method to measure the shrinking temperature (Ts) by video analysis using fish skins of 22 species and examine the relationship among the Ts, Tp, and Td of type I collagen in each fish species. The Ts showed a high correlation with the Tp of each fish species. The Ts of each fish species was approximately 26 °C higher than the Td of type I collagen from the same fish species. In addition, Ts was highly and positively correlated with the content of Pro and Hyp in type I collagen but negatively correlated with the content of Ser. These results indicated that fish Ts can be easily measured by video analysis and that it varies depending on Td, which is mainly determined by the content of Pro, Hyp, and Ser in collagen molecules in the skin. This method can be utilized for checking the integrity of skin collagen, particularly from cold-water fish.