Heart rate and gill ventilation in ovigerous and non‐ovigerous edible crabs,Cancer pagurus: The effects of disturbance, substrate and starvation

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Abstract
This study compared the cardiac and ventilatory behaviour of disturbed and settled (48 h recovery) ovigerous Cancer pagurus with the behaviour of non‐ovigerous crabs. It also examined the effects of starvation and a sand substrate on ovigerous females. Ovigerous crabs had significantly lower heart rates than non‐ovigerous crabs. This implies that they have a reduced metabolic rate, confirmed by an earlier study which described lower rates of oxygen uptake in ovigerous crabs. Scaphognathite beat frequency was unaffected by either the presence of eggs, starvation or a sand substrate, but the amplitude of ventilatory pressure changes was higher in settled ovigerous females, implying greater force. The duration of periods of reversed ventilation was also substantially extended in ovigerous crabs, and disturbance caused a ten‐fold increase in the frequency of these reversals, resulting in ventilation being carried out in a predominantly reversed direction. It is suggested that these respiratory adaptations serve to ventilate the egg mass. Disturbance also led to a greater elevation of heart rate in ovigerous crabs, indicating that they are more prone to handling stress. Fed ovigerous crabs spent a higher percentage of time ventilating unilaterally; this response was lost following starvation. Starved ovigerous crabs had the lowest mean heart rate, highest mean ventilatory pressures and, when disturbed above a sand substrate, they showed the highest frequency of reversals of ventilation, possibly in association with their efforts to bury their abdomen bearing the egg mass.