Nothing. Bioluminescent animals are also made of meat like we are, if they release too much heat, they would cook themselves. Most bioluminescence are from the breakdown of luciferin by a luciferase and the reaction tends to be very efficient, so very little waste heat is produced. We very commonly use bioluminescence for experiments, I have personally done a lot of experiments with genetically modified flies that would produce bioluminescence upon feeding of luciferin