Chapter 18 - The Physiology of Gas Exchange, Circulation, Ion Regulation, and Nitrogenous Excretion: An Integrative Approach

Abstract

This chapter focuses on three interrelated physiological processes. Gas exchange encompasses the structure and function of gills, the generation of the ventilatory stream, oxygen uptake and transport, CO2 transport and elimination, acid-base balance, and respiratory control. Circulation encompasses heart structure, heart excitation and dynamics, control of heart performance, vascular function in an open circulatory system, and control of both heart performance and regional blood flow. Osmotic and ionic regulation and nitrogenous excretion involve discussion of the structure and function of the three major regulatory systems: the gills, the antennal glands, and the alimentary tract. The functioning of these systems is discussed for quiescent animals under natural conditions, in activity, and in response to environmental and other stressors. It is designed to reveal these interrelationships and their integration within the overall responses of H. americanus to environmental perturbations and changes in the activity level. This chapter also explains and reviews structure and function of the gills, gill ventilation, oxygen uptake, hemolymph gas and acid-base levels, functioning of hemocyanin, carbon dioxide elimination and acid-base balance, and the periods of intermittent ventilation (pauses). The anatomy of the open circulatory system of crustaceans is reviewed and is described for Homarus americanus. Integrated respiratory and circulatory responses, physiological compensation and osmotic and ionic regulation, and nitrogen excretion are the topics of discussion in the later parts of this chapter.