Fig. 2.

The brain and vascular network both generate action potentials and both express genes homologous to those associated with voltage dependent sodium and calcium channels in vertebrate nervous systems. Simultaneous recordings from an ampulla of the vascular network (A) and the mature brain of a nearby zooid (B) at stage A3. In this example, the ampulla exhibits rhythmic firing that is not seen in the neural record. Action potentials at the two sites were neither simultaneous nor phase-locked. (C) Expression patterns of putative homologous genes associated with human voltage-dependent sodium and calcium channels in the brain and ampullae of B. schlosseri (x-axis). Each gene is represented by a single row in the heatmap, where blue indicates low expression and red indicates high expression in log₂cpm. The gene annotation is noted next to the B. schlosseri unique gene identifier (g). The columns indicate the tissues sampled (brain or ampulla) and the blastogenic stage. Although most of the candidate homologs are continually expressed in brain tissue throughout the neurodegeneration cycle, only a subset of the genes associated with sodium channels are expressed in the ampullae.