Musseling in on novel cryoprotectants.

Musseling in on novel cryoprotectants

Cryobiologists have long known that many insects and some frogs are equipped with compounds that protect them against the damaging effects of freezing. Bivalve mollusks and other invertebrates that live near shore also weather frigid temperatures and are able to survive the presence of ice in their extracellular fluids. But until recently, scientists had been unable to find any similar cryoprotectants in these animals.

Stephen Loomis at Connecticut College in New London and John Carpenter and John Crowe at the University of California at Davis report that they have identified at least two novel compounds in the blood of winter-acclimatized blue mussels, which protect one kind of membrane and two enzymes against freezing and thawing damage. In a systematic purification process, they identified taurine, which previously had been shown to stabilize membranes under nonfreezing conditions, and strombine, which is produced when the animal shuts its shell, sealing off its access to oxygen. Loomis says that the finding of strombine may explain past reports than linked such anaerobic conditions to increased freezing tolerance of the animal.

Past efforts to find a cryoprotectant in these intertidal organisms failed because scientists had only searched for well-known cryoprotectants such as glycerol, he says. With his group's method of systematically separating components of blood by size and weight and then testing their cryoprotective properties, Loomis hopes to identify new cryoprotectants in other freeze-tolerant animals such as a tidal marsh snail. His group is also working to understand exactly how the recently found compounds may protect the blue mussel from the ravages of freezing and thawing.