ICE NUCLEATION IN THE BLUE MUSSEL (MYTILUS-EDULIS)

The ice nucleation temperatures of different homogenised organs of the mussel Mytilus edulis L. were examined. The stomach and the hemolymph had the highest nucleation temperatures. In the homogenised stomach t he nucleation temperatures were fairly constant throughout the year, w hereas the nucleation temperatures of the hemolymph increased in the c old season. Bacterial growth experiments, microfiltration, and experim ents using antibiotics indicated that the nucleators were not of bacte rial origin. The nucleation temperatures of natural seawater were appr oximately -9 degrees C, whereas seawater made from distilled water and sea salt had nucleation temperatures of about -17 degrees C. The nucl eation temperatures of the seawater were reduced when the seawater was filtered by the mussels. However, no clear indication that the nuclea tors in the stomach were obtained from the seawater was found. Stomach homogenates from mussels kept in nucleator-free water had the same su percooling points as stomach homogenates from mussels kept in natural seawater. This indicates that the nucleators in the stomach are not ob tained from the seawater. The temperature and light conditions examine d in the present study did not significantly influence the hemolymph i ce nucleation temperatures of mussels kept in the laboratory.