Oxygen Isotopic Composition of Phosphate from Shells of some Living Crustaceans

Abstract

RECENTLY one of us1 reported some results of measurements of the oxygen isotopic composition of phosphate from shells of living marine organisms. Four of the specimens measured were crabs and from the results obtained it was inferred that biological fractionation effects are involved in the process of precipitation of the calcium phosphate of crab shells. It was important to have better information of the behaviour of crabs in this regard in view of the possible utilization of fossil specimens for palaeotemperature measurements on phosphates. For this reason, some crabs were grown under controlled temperature conditions. Some ten specimens of Carcinides maenas Rath. (Carcinus maenas) were maintained in a thermostatic bath with a continuous inflow of sea water. The reasons for this were: (a) to maintain the oxygen isotopic composition of the water at a constant value it is essential to reduce the effects of evaporation; (b) that it is necessary to provide a continuous supply of sea water just in case crabs precipitate (at least partially) their calcium phosphate directly from sea water.