Structural and ultrastructural (Electron microscopy) contributions to the dolphin’s hypophysis

Abstract

The growing scientific interest in the health and welfare of cetaceans, as important species both in the context of ecosystem balance and environmental indicators and as animals kept under human care, has given rise to a myriad of studies in different veterinary fields. The main component in the regulation and development of the stress response system, among many other physiological and behavioral processes, is the Hypothalamic-Pituitary-Adrenal Axis (HPA Axis) in the neuroendocrine system. This often-forgotten system is made of a set of neurons, glands, and non-endocrine tissues that play a critical role in the adaptation processes an animal undergoes, therefore being potential indicators of both health and welfare. As a first step to set light on the intrinsically complex HPA Axis, better understand its functioning and improve its evaluation, we need to deepen the study on its poorly understood chore components. Through the present work, we have taken a closer look into the organism’s master gland, the hypophysis; by firstly standardizing a post-mortem methodological assessment for cetaceans; secondly studying its morphological, histological and immunohistochemical characteristics with light microscopy; and thirdly having a closer look into the ultrastructural characteristics of the gland and its different cell types using electron microscopy in two pituitary glands from two dolphin species (Tursiops truncatus and Stenella coeruleoalba).