Neurocalcin-like immunoreactivity in embryonic stages of Aplysia californica and Lymnaea stagnalis

Neurocalcin is a calcium-binding protein that has been localized in neural and non-neural tissues of vertebrates, the arthropod Drosophila melanogaste r, and in juveniles and adults of the mollusc Aplysia californica. We exami ne the distribution of neurocalcin in pre-hatching stages of the molluscs A . californica and Lymnaea stagnalis to elucidate where this calcium-binding protein functions in early development, as well as to localize novel neuro nal populations in early stages of ontogeny. Apl,sia neurocalcin (ApNc)-lik e immunoreactivity was localized in shell-secreting cells in embryonic stag es of both A. californica and L. stagnalis. In A. californica, central and anterior regions of the embryo were diffusely labeled, as were a few identi fiable neurons in veliger stages. On the other hand, in L. stagnalis, ApNc- like immuno-reactivity was clearly detected in cells and fibers in the same locations as neuronal elements that have been previously identified very e arly in development and throughout the embryonic period using techniques to localize specific transmitters and peptides. Furthermore, additional neuro ns are also identified with anti- ApNc in this species. Establishing the di stribution Of neurocalcin-like proteins in embryonic stages of these two mo lluscs provides the first step to understanding the role of such proteins d uring development.