ABSTRACT
Scanning electron micrographs of sections of the prismatic shell of the bivalve Mercenaria mercenaria reveal narrow subdaily growth striations. The width of these narrow lines, formed by concentrations of organic material, corresponds to the quantity of shell material that would be expected to dissolve during periods of anaerobic metabolism. The pH in the extrapallial fluid of the bivalve decreases when the valves are closed, and the amount of dissolution of shell is related to the duration of valve closure.
ABSTRACT
A discrete, calcareous layer that binds the foliated calcite of the oyster's shell to the organic ligament in the hinge is reported, apparently for the first time. This layer is ultrastructurally, and generally mineralogically, different from the underlying foliated calcite, and is named the ligostracum.
ABSTRACT
Recent development of a microelectrode has enabled the first continuous recording of the pH of the secretion of the normally functioning accessory boring organ of the shell-boring predatory snail Urosalpinx. The recording was made in an incomplete borehole in a glass-shell model. The minimum pH recorded was 3.8; hitherto the secretion had been considered neutral.