ABSTRACT
The eld of “elasmobranch endocrinology” began at the same time as the eld of vertebrate endocrinology itself, when Bayliss and Starling (1903) used extracts from the intestines of sharks and skates to demonstrate the actions of secretin, the rst described vertebrate hormone. Although perhaps coincidental, a pivotal role for sharks and their relatives in the birth of this eld is prophetic to some extent, given that many vertebrate hormones appear to have rst appeared in the cartilaginous shes. Because sharks and their relatives occupy such a critical position in the evolution of the vertebrate endocrine system, studies on endocrinology of these shes contribute to a better understanding of the roles that hormones exert in all higher vertebrates. Furthermore, because hormones regulate virtually all aspects of elasmobranch physiology, knowledge concerning the function of the elasmobranch endocrine system is essential for developing a full comprehension of how these shes develop, grow, reproduce, and survive.
