Slugging It Out!

It's funny how some ideas in science achieve popularity; fade away and then re-appear decades later. I remember working on a molecule ('scotophobin') that was said to transfer fear of the dark between animals (I thought it might be simply a derivative of the hormone ACTH and tested it on goldfish). At the time, sea-slugs were favourite animals for research on 'learning molecules'. There is now a claim from workers with Aplysia (a sea-slug) that 'knowledge' of 'painful' electrical shocks (from implanted tail electrodes) can be transferred to another member of the species by injecting generated ribonucleic acid (RNA), causing the animal to retract its siphon (https://www.theguardian.com/science/2018/may/14/scientists-transplant-memories-between-sea-snails-via-injection). RNA from slugs who were implanted with electrodes but did not receive shocks did not produce this response. RNA is, of course, a molecule that is used to generate particular proteins (so the protein may be the signal for this simple 'memory').