Aspects of the hormonal regulation of appetite in fish with emphasis on goldfish, Atlantic cod and winter flounder: Notes on actions and responses to nutritional, environmental and reproductive changes

In vertebrates including fish, food intake regulation involves intricate networks of hormones produced by both brain and peripheral tissues. Under optimum conditions, nutritional intake is adequate for basal metabolic needs, growth, development, reproduction, and deposition of energy stores. As fish represent a very diverse group, different fish species live in very different environments and are exposed to variations in a wide range of factors, including not only internal factors, such as nutritional/metabolic status and reproductive events but also environmental factors, such as temperature and photoperiod. These physiological responses often include changes in appetite that might occur through modulations of the gene expression and action of feeding-regulating hormones. Despite recent advances, our current understanding of the regulation of feeding in fish is still limited and based primarily on studies involving a few fish species. This review will give a brief overview of our current knowledge of the regulation of feeding by three central (NPY, OX and CART) and two peripheral (ghrelin and GRP) appetite-related factors in a freshwater species, the goldfish (Carassius auratus) and two marine species, cod (Gadus morhua) and winter flounder (Pleuronectes americanus).