The blackening of sea rabbits may be due to the fact that sea rabbits contain sea rabbit ink, which is a substance used by sea rabbits to protect themselves from foreign toxins. Sea rabbit ink is a black particle in the body of sea rabbits, which may affect the surrounding environment of sea rabbits and make the surrounding water black. In this case, the sea rabbit will turn black, but this change is only temporary. When the sea rabbit leaves the protection range of the ink sac, the color will gradually return to normal.

In addition, if you don't clean the sea rabbit thoroughly when cooking, the remaining ink sac may also cause the sea rabbit to turn black. Therefore, before cooking sea rabbits, they should be soaked in clear water for a period of time to clean the dirt and impurities on their surfaces.

In a word, the blackening of sea rabbits is usually caused by their own protection mechanism or failure to clean them thoroughly before cooking, but this will not affect their edibility. If you have doubts about this, it is recommended to consult local food safety agencies or professionals.