Effects of feeding on the respiration of ectothermic vertebrates

Introduction Many ectothermic vertebrates are opportunistic carnivores that ingest large meals at irregular intervals (Greene 1997, Secor and Diamond 1998, 2000, Secor 2001, Secor and Boehm 2006, Cocker-Butar and Secor 2014). Interspecific differences in feeding habits give rise to specific adjustments in a number of physiological processes directly or indirectly involved in the digestion and absorption of nutrients (Secor 2001, Wang 2001, Wang et al. 2001, McCue 2006, Secor 2009, and see also Chapter 4 in this book). The ingestion of large meals in some ectotherms is followed by an steep rise in the secretion of digestive fluids and in the capacity for intestinal assimilation and, in some cases, by changes in the relative size of the organs involved in the digestive processes (Wang et al. 2001, Secor 2009). Associated with such events, there is a considerable increase in the energy requirement during the postprandial period leading to cardiorespiratory adjustments to ensure an adequate supply of oxygen (Wang et al. 2001, Andersen et al. 2005, McCue 2006). Despite the fundamental importance of these adjustments to match the increased energy demands associated with meal digestion, while correcting ionic and acid/base disturbances, very little is known about the mechanisms that coordinate the cardiovascular and respiratory changes during the postprandial period. In this chapter, we will first review the nature of the changes in energy demand associated with feeding in different groups of ectotherms and then examine what is known about the cardiorespiratory changes associated with them.