EARLY FMRFAMIDE-LIKE IMMUNOREACTIVE CELLS IN GASTROPOD NEUROGENESIS

The somata of the first FMRFamide-like immunoreactive (Fa-LIR) cells a ppear early during neurogenesis and are located posterionly within the embryo. By the time that Aplysia californica hatches into a free-livi ng veliger, it already contains 3 intensely immunoreactive cells with fibres which project anteriorly to cross the cerebral commissure and i nvade the developing pedal ganglia. Fa-LIR elements are also present b y 30-33%, of embryonic development in Lymnaea stagnalis, which hatches as a fully metamorphosed juvenile. The cells in L. stagnalis, are sim ilarly located posteriorly in the embryo and have fibres which project to the cerebral and pedal ganglia. These findings suggest that such F a-LIR cells are among the very first to develop within the gastropod n ervous system and that they may be play important roles in subsequent neuronal development.