|Freezing tolerance of marine invertebrates|
Loomis, S.H. (1995). Freezing tolerance of marine invertebrates. Oceanogr. Mar. Biol. Ann. Rev. 33: 337-350
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218, more
Cold tolerance; Marine invertebrates; Marine
Intertidal invertebrates living in temperate regions of the world are generally freezing tolerant, and must be able to limit the osmotic and mechanical damage to their tissues that results from freezing of the extracellular fluids. General mechanisms of protection include production of proteinaceous ice nucleators, antifreeze proteins, cryoprotectants, changes in the composition of membrane phospholipids and metabolic rate reduction. Various intertidal invertebrates, including Melampus bidentatus, Littorina littorea, Geukensia demissus, Mytilus edulis, and Balanus balanoides, utilize these strategies to greater or lesser extents. All have seasonal changes in the extent of their freezing tolerance that most likely results from seasonal presence of ice nucleators (either proteinaceous or bacterial) and cryoprotectants (which may be related to exposure to anaerobic conditions). All also have a lower metabolic rate in the winter resulting from exposure to lower temperatures. However, Mytilus collected in Norway appears to be the only intertidal invertebrate for which antifreeze proteins may play a role in freezing tolerance, although there is some question of the significance of these findings, since no antifreeze proteins were found in Mytilus collected from Connecticut or Massachusetts. Changes in the composition of membrane phospholipids (especially sphingomyelin) have been correlated with changes in freezing tolerance in Balanus balanoides, but little is known of this strategy in other intertidal invertebrates.