Figure 5. C2 characteristics in Hermissenda crassicornis.

A. Backfilling the pedal commissure with biocytin labeled 3–4 neurons near C2_Herm (left). Only the cerebral-pleural ganglion contralateral to the backfilled nerve is shown. FMRFamide-like immunohistochemistry labeled C2_Herm (middle). Combining FMRFamide-like immunoreactivity with the backfill revealed just one neuron, C2_Herm (right). B. C2_Herm could be identified visually due to its characteristic white soma (black arrow) near the origin of cerebral nerve 1 (CeN1, white arrows). Note the white cell just medial to C2_Herm (orange arrow). An asterisk (*) labels the statocyst. Only one cerebral-pleural ganglion is shown. C. Filling the C2_Herm soma with biocytin revealed a contralateral axon projection through the anterior cerebral-pedal commissure (not shown) and into the pedal commissure (PP2). The example is a representative image in which the outline of the brain and the axon projection were traced for ease of viewing. D. C2_Herm (arrow) was filled with biocytin (left). It was immunoreactive for both FMRFamide (middle) and SCP_B (right) as shown. The white cell just medial to C2_Herm is immunoreactive for FMRFamide, but not SCP_B (orange arrow).