Calorimetric Heat Dissipation Measurements of Developing Zebrafish Embryos

Living cells, tissues and organisms are open, metabolically active systems that constantly exchange matter and energy with their environment in the form of heat. The heat exchanged is equal to the net enthalpy of all chemical reactions taking place within the system. Thus, heat dissipation can inform on the energetic costs of the constellation of cellular processes that contribute to physiology and address unanswered questions about development, responses to the environment, signaling and metabolic pathways, and the roles of morphological substructures. Here, we describe the methods we established to measure the heat dissipated by early zebrafish embryos undergoing synchronous cell cycles of cleavage stage embryogenesis, using isothermal calorimetry. The non-invasive nature of calorimetry and the versatility of these methods enables the investigation of the energetic costs of embryonic development and of the cellular processes associated with the early embryonic cell cycles.