Characteristics of resting ventilation and response to hypoxia, hypercapnia, and emersion in the blue crab Callinectes sapidus (Rathbun)

Abstract

AbstractVentilation volume was monitored in the blue crab Callinectes sapidus using an electromagnetic flow probe. The mean resting ventilation volume for a 200 g crab was 111 ± 78 ml. min−1, mean oxygen consumption was 62 ± 27 ml. kg−1. hr−1, and mean extraction efficiency was 53 ± 15%. Blue crabs continued to ventilate in air for at least eight hours at room temperature and were able to maintain oxygen consumption during exposure to air. The crabs did not change ventilation, oxygen consumption or extraction efficiency significantly in response to hypercapnia (7.5 or 15 torr Pco2), whether breathing air, fresh water, or sea water. Ventilation increased 37% at reduced oxygen tensions (24–65 torr), but since the extraction efficiency remained the same, oxygen consumption fell more sharply at lower O2 tensions. Pecularities of the ventilatory system, such as apnea, reversals, unilateral apnea or reversals, and variable phasing of the two scaphognathites were observed. Ventilation volume varied linearly with scaphognathite frequency and pressure differential; the scaphognathite stroke volume and gill sieve resistance appeared to be constant.