Animal bioenergetics: Thermodynamic and kinetic analysis of growth and metabolism of Anguilla anguilla

Bioenergetics and biothermodynamics are valuable tools in research on growth and metabolic processes of a wide range of organisms, including viruses, bacteria, fungi, algae and plants, as is shown by the many publications on this topic in the literature. These studies provide insight into growth and metabolism of individual species, as well as interactions between species, like the virus-host interaction (infection) and virus-virus interaction (competition). However, this approach has not yet been applied to animal species. The universality of biothermodynamics and bioenergetics provides a good motive to apply them in analysis of animals. In this research, we made a bioenergetic, biothermodynamic and kinetic characterization for the first time for an animal species – Anguilla anguilla L. (European eel). We made a comparative analysis on yellow (young adult) and silver (mature adult) phases. Metabolic processes were modeled as chemical reactions with characteristic thermodynamic properties: enthalpy, entropy and Gibbs energy. Moreover, Gibbs energy explained growth rates, through phenomenological equations. This analysis of animal metabolism and growth explained metabolic properties of yellow and silver A. anguilla, including the bioenergetic aspect of life history. Moreover, we compared thermodynamic properties of A. anguilla with those of its main macromolecular components and other organisms. The thermodynamic properties were explained by the structural properties of organisms. This research extends the bioenergetic and biothermodynamic approaches to zoology, which should allow analysis of the energetic aspect of animal metabolic processes, interactions with their environment and interactions with other organisms. Furthermore, it connects the macroscopic perspective of zoology with the microscopic perspectives of biochemistry, bioenergetics and biothermodynamics. This will provide a basis for development of mechanistic models of animal growth and metabolism.