Environmental cycles and biological rhythms during early development

Abstract

The environment in which aquatic organisms inhabit is not constant and many factors such as light and temperature display cyclic and predictable variations. Animals present biological rhythms in many of their physiological variables to adapt to these cyclic changes, timing their functions to occur when the possibility of success is greater. Besides, the underwater photo-environment is complex since light characteristics (i.e. intensity and spectrum) are variable and depend on the absorbance properties of the water column. Fish development is hence highly influenced by all of these factors, affecting processes such as survival, growth, hatching, sex determination/differentiation and occurrence of malformations. The aim of this chapter is to review how fish development and performance is shaped by environmental factors, paying special attention to the effects of environmental cycles of light and temperature, the characteristics of illumination and the role of the developing biological clock.