Distribution of cells containing FMRFamide-related molecules in the embryonic development of Ophryotrocha labronica (Polychaeta: Dorvilleidae)

The timing and spatial distribution of cells containing FMRFamide-related molecules in the embryogenesis of the polychaete Ophryotrocha labronica were studied immunocytochemically. FMRFamide-like molecules emerge early during embryonic development. They are found at the one-cell stage, are asymmetrically distributed in the first phases of cleavage, associated with gastrular movements, and label the central nervous system morphogenesis. Moreover, during embryogenesis, the pattern of gut cells with the FMRFamide-likephenotype that is present in adults is already established. The early occurrence of FMRFamide-like molecules in O. labronica suggests that these molecules are involved as pre-nervous growth signals in the regulation of basic neuronal cell behaviors.