Meeting Abstract
Octopuses exhibit behavioral flexibility and demonstrate a remarkable ability to learn and remember, which is the result of a centralized nervous system containing about 500 million neurons. Cephalopod nervous system centralization is an example of convergent evolution, with parallel centralization events occurring multiple times throughout evolutionary history. The learning and memory circuit present in Octopus is located in the vertical lobe and contains three different categories of neurons: superior frontal lobe cells, amacrine interneurons, and large efferent neurons. For this project, we examined secretory molecules (neuropeptides and classical neurotransmitters) present in the memory forming circuitry of Octopus and localized them in Octopus neural tissue. Using standard molecular cloning techniques and in situ hybridization, we effectively identified and localized three new neuropeptide molecules in vertical lobe circuit cells, one of which labels presynaptic superior frontal lobe cells while the other two label large efferent neurons. Additionally, we identified two of the first markers for glial-like cells in Octopus. We also cloned Nitric Oxide Synthase for the first time in Octopus and identified both nitric oxide and dopamine (via Aromatic-L-Amino Acid Decarboxylase) as potential vertical lobe neurotransmitters. Considering these findings together, the independent evolution of Octopus brains appears to have employed a unique combination of both neuropeptides and classical neurotransmitters, broadening our understanding of convergent evolution in distant phyla as well as revealing new questions to address in the future.
