THE EFFECT OF OXYGEN-TENSION ON THE SWIMMERET RATE OF CALLIANASSA-AUSTRALIENSIS AND C-ARENOSA (CRUSTACEA, DECAPODA, THALASSINIDEA)

Previous workers have concluded that callianassid burrow ventilation r epresents a reflex response to declining oxygen tension. However, C. a ustraliensis increases swimmeret rate when anoxic, whilst C. arenosa r esponds differently by increasing swimmeret rate as oxygen tension fal ls (as predicted by the reflex model). None of the shrimps ceased swim meret ventilation in anoxic conditions. When oxygen tension was raised after 3-4 h of anoxia, C. australiensis showed a significant fall in swimmeret activity. The oxygen reflex model cannot apply to all callia nassids because many species use burrow ventilation for sediment purgi ng as well as burrow oxygenation. Differences between species may aris e because of variation in environment, feeding behaviour and anoxia to lerance.