BEHAVIORAL AND RESPIRATORY ADAPTATIONS OF THE MUD-BURROWING SHRIMP CALOCARIS-MACANDREAE BELL (THALASSINIDEA, CRUSTACEA) TO THE BURROW ENVIRONMENT

The thalassinid shrimp Calocaris macandreae Bell is an important component of the benthic communities of many Scottish sea-lochs. Along with others, this species constructs large, semi-permanent burrows in soft muds. Oxygen availability within burrows constructed by individual C. macandreae in aquaria was found to be severely and chronically low (PO2 as low as 15 Torr). The behaviour patterns displayed by C. macandreae in laboratory burrows were analysed using video recordings. In general, behaviour was characterized by low levels of activity, with burrow irrigation by pleopod beating being infrequent and of short duration. During experimental depletion of oxygen availability, however, burrow irrigation was increased. In view of the hypoxic conditions encountered by C. macandreae, an investigation of respiratory physiology in this species was made. Open and closed respirometry techniques indicated that the rate of oxygen consumption by C. macandreae was low compared to that of most other decapods (but similar to those recorded for other thalassinids). Oxygen consumption was maintained at a constant rate even at very low oxygen tensions with a 'Pc' of between 10 and 20 Torr. Measurement of heart and scaphognathite rates using an impedance technique showed that hyperventilation was a consistent response to environmental hypoxia, although there was a less pronounced response of heart rate.