Respiratory adaptations in intertidal fish

Abstract

SYNOPSIS: Intertidal rockpools provide a challenging environment for rockpool fish with rapid changes taking place in many environmental parameters over a tidal cycle. Intertidal fish exhibit a number of behavioural adaptations such as the avoidance of hypoxic situations or remaining inactive during aerial "stranding." Other species are, however, well adapted to breathe air and exhibit morphological adaptations such as smaller gill areas, specialized buccopharyngeal epithelia and a proliferation of cutaneous blood vessels in the skin. Oxygen consumption in rockpool fish is comparable to non-intertidal fish and responds in a similar manner to temperature changes. The ability to regulate oxygen consumption down to oxygen tensions below 40 Torr is, however, marked in rockpool species. Aerial and aquatic rates of respiration are similar in those species which are able to breathe air and the respiratory quotient normally remains between 0.7 and 0.9. A number of intertidal fish are well adapted for cutaneous respiration, satisfying over half of their oxygen and carbon dioxide exchange through the skin. Ventilatory responses to increased temperature, hyperoxia and hypoxia are similar to those of other fish but cardiac responses may differ in that no change in heart rate is seen under hypoxia or hyperoxia. Ventilatory and cardiac responses to aerial respiration are well adapted in some species maintaining ventilation and perfusion during aerial exposure. A marked Bohr effect, low temperature sensitivity and a temperature dependent Haldane effect have been measured in the haemoglobolin of some intertidal fish. These properties may assist oxygen transport and carbon dioxide exchange during cyclical changes in environmental parameters within an intertidal rockpool. © 1988 by the American Society of Zoologists.