Salinty tolerance and osmoregulation of the Australian freshwater crayfish Cherax destructor Clark (Decapoda : Parastacidae)

Abstract

The lethal and sublethal effects of increased salinity on adult and juvenile crayfish, and the effects of increased salinity on osmotic behaviour of adult crayfish were investigated. Lethal experiments, using a wide salinity range, indicated little difference in the salinity tolerance of adults and juveniles, but when 96-h median tolerance limits were estimated using a narrow salinity range: the juvenile value was 25. Sow while that for adults was 29.90‰. Sublethal effects, as determined by 'threat' and 'escape' behavioural responses with increased salinity, indicated that normal behaviour in adults and juveniles is maintained up to c. 12‰, lost between c. 12 and 25‰,. and death results above c. 25‰,. It is suggested that the field salinity tolerance range of C. destructor is restricted to salinities where behavioural patterns are unaffected. C. destructor is a hyperosmotic regulator, maintaining its blood concentration at approximately 410 mOsm up to 14‰, above which the blood concentration follows the isosmotic line. The possible evolution of this species is briefly discussed in terms of osmotic behaviour.