Biomineralization and Systematic Implications

Abstract

Nautilus is the only cephalopod with an external, camerated shell composed of calcium carbonate (CaCO₃). Interest in the chemistry of the calcified structures of Nautilus has developed slowly during the past three decades, but sufficiently to provide insight into the chemical relationship of calcified structures, cephalopod biomineralization, and the physiology of Nautilus. Understanding the skeletal chemistry of Nautilus provides a means of studying the cephalopod physiochemical system, which facilitates the exploration of four factors: (1) the differences in the genetic makeup of the physiochemical system responsible for CaCO₃ production among species and populations, which forms the basis for biochemical taxonomy and its phylogenetic implications; (2) the ontogenetic variation in the chemistry of shell aragonite and its possible relationship to the life cycle of Nautilus; (3) the concentrations of trace elements in skeletal carbonate unrelated to CaCO₃ production, which serve as indicators of nutrient concentrations in seawater; and (4) the implications of all aspects of Nautilus chemistry for the study of similar problems in extinct cephalopods, the skeletons of which have survived in a chemically unaltered state.