Meeting Abstract
How did the simple nervous systems of basal invertebrates elaborate into complex brains? It is reasonable to assume that simple decision making circuits developed into complex ganglia, but this hypothesis remains untested. We explore this question by comparing the transcriptome and peptide profiles of analogous central nervous system (CNS) regions of different invertebrates. If analogous CNS regions are in fact homologous, then they may have similar profiles among related species. These profiles likely become less similar with greater evolutionary distance between species, but structurally conserved peptides should still be traceable in comparative analyses. As a starting point we are characterizing the peptide profiles of critical neurons in the nudipleuran Pleurobranchaea californica. Using mass spectrometry, we have characterized profiles for three neurons: the A1 cell (element of the Turn/Locomotor/Swim network), the buccal ganglion ventral White Cell (feeding command cell), and the buccal ganglion “Efference Copy” cell (provides efference copy of feeding motor activity to the stomach). We find that A1 contains FMRFamide and multiple peptides homologous to Aplysia pedal peptides 3 and 4, the buccal Efference Copy cell contains only LFRFamide and related peptides, and the Ventral White Cell contains multiple peptides including the myomodulins. These results establish a reference point for comparison with other species, in particular other gastropods. Analogous cells have been found in other gastropods, notably Tritonia and Aplysia, enabling us to both look for homologies in peptides and determine if evolutionary distance predicts differences in peptide profiles.
