TEMPERATURE RELATIONSHIPS OF POIKILOTHERMS AND THE MELTING TEMPERATURE OF MOLECULAR COLLAGEN

Abstract

The molecular unit of collagen, the main fibrous protein of connective tissue, undergoes a first order phase transition at a characteristic temperature, when heated in physiological saline. For the collagen of mammals this temperature is known to almost coincide with the deep body temperature of the animal, and for a number of poikilotherms, with the upper limit of their environmental temperature. We have measured the transition temperature of the collagens of a number of worms and now report that:1. The molecular unit of the collagen of two hog intestinal worms undergoes this transition at temperatures close to that of the body of their host.2. For a number of earthworms for which there are precise data on thermal preference limits, the molecular unit of the collagen of these animals has a transition temperature which is very close to the upper limit of the thermal preference zone.3. There is no evidence of any causal relation between the transition temperature of molecular collagen, and the abrupt physiological and behavioral changes which become apparent at the same temperature. However, the results are direct evidence of a specific protein having easily measurable thermal properties which reflect thermal properties of the whole animal.