USING DIFFERENTIAL SCANNING CALORIMETRY TO STUDY FREEZING IN A EURYHALINE AQUATIC INVERTEBRATE

Differential scanning calorimetry was used to study the cryobiological characteristics of nauplii of the euryhaline aquatic brine shrimp Art emia salina acclimated to three salinities (5, 35 and 70 parts per tho usand). There was no significant difference in the supercooling points (SCP) or freezable water contents of samples from the three salinitie s. Mean SCP values ranged from -21 to -22.5 degrees C. Mean melt onset temperatures and melting points differed significantly with samples a cclimated to 5 parts per thousand having considerably higher melting p oints than those from 35 or 70 parts per thousand. These results are d iscussed in relation to the hyper-hypo ionic osmoregulation shown by A rtemia and compared with data for the harpacticoid copepod Tigriopus b revicornis, which is an osmoconforming species. The study emphasizes h ow the osmotic physiology of such a euryhaline invertebrate affect sit s supercooling ability and hence its survival in freezing conditions.