What underlies CO2-induced behavioural changes in squid?

Our new paper pharmacologically demonstrates that GABA-A-like receptors and other ligand-gated chloride channels may underlie elevated CO2-induced behavioural alterations in squid.

We exposed two-toned pygmy squid (Idiosepius pygmaeus) to ambient or elevated CO2 levels followed by treatment with sham, gabazine (blocks GABA-A receptors) or picrotoxin (blocks molluscan GABA-, glutamate-, acetylcholine- and dopamine-gated chloride channels).

After treatment, squid behaviour was measured when placed in a tank with a mirror. We found that elevated CO2 increased squid activity levels. The squid’s attraction to, and aggressive behaviours directed toward, their mirror image were also increased at elevated CO2.

Our results suggest that altered functioning of GABA-A-like receptors underlies some of these CO2-induced behavioural changes in squid. Using both gabazine and picrotoxin provides more robust support for this GABA hypothesis.

By using picrotoxin, we also showed for the first time in any marine invertebrate that ligand-gated chloride channels, other than the GABA-A receptor, may be involved in some of these behavioural changes at elevated CO2.

Overall, our results suggest that multiple mechanisms underlie CO2-induced behavioural changes. We propose that elevated CO2 leads to a suite of changes within the nervous system. This can potentially explain the variability in the behavioural effects of elevated CO2.

Paper

Thomas, J. T., Spady, B. L., Munday, P. L., & Watson, S. A. (2021). The role of ligand-gated chloride channels in behavioural alterations at elevated CO2 in a cephalopod. Journal of Experimental Biology. DOI: 10.1242/jeb.242335