Crustacean nociception: Origins, part 1

As I mentioned before, our new paper in PLoS ONE took a very long and winding road from idea to publication.

As an undergraduate, I helped my supervisor, Jennifer Mather, prepare a talk, “Ethical treatment of invertebrates: how do we define an animal?” Jennifer wanted to speak on this partly because Canadian Council of Animal Care guidelines had listed experiments with invertebrates at the same ethical level of concern as vertebrate tissue. Interestingly, that’s where most invertebrates remain to this day (see Appendix XV-B), although there are increased concerns for “cephalopods and some other higher invertebrates.”

I helped Jennifer make some slides for her presentation. I drew some cartoons on them for fun; things like a clam saying, “Where did the expression ‘Happy as a clam’ come from?” The talk was given at an Animal Behavior Society symposium (first conference I went to!). Her talk was ultimately published. ^* So I started thinking about invertebrates, their nervous systems, and what that implied for their care, early in my academic career.

In 2001, Ed Kravitz wrote an article for the International Society for Neuroethology newsletter. He described the experience of being interviewed on TV as part of a story about the ongoing question of whether boiling lobsters is inhumane.

In response to the question of whether lobsters feel pain, I said that we didn’t know.

Emphasis added. Of course, because Ed is a scientist, he went on to give a longer, more thorough answer.

I added that since pain is a perception we often don't know whether people feel pain either, unless we ask them, and that pain thresholds vary greatly among individuals. I mentioned that pain is a higher cortical function in humans and that there is no structure resembling a cortex in the lobster brain. In response to questions about the many minutes of suffering and struggling by lobsters to get out of pots of boiling water, I mentioned that neurons in the lobster brain cease to function at temperatures above 27° Celsius (about 80° Fahrenheit) and that in boiling water the brain would quickly reach that temperature. I felt it highly unlikely, therefore, that the banging around in the pot was struggling to escape and instead suspected that heat-induced contractions of the massive tail and limb musculature of already brain-dead animals was the cause. In case people were still worried about the suffering issue, however, I mentioned that after cooling an animal on ice to anesthetize it, the brain of a lobster could be immediately destroyed with a scissors cut between the eyes.

Ed’s answer was correct, but it still bugged me. It bugged me we didn’t have an answer backed by good evidence, just extrapolations and guesses (albeit educated geusses). People had studied crustacean nervous systems intensively for decades. You can find beautiful pictures of lobster brains by Gustaf Retzius from the nineteenth century. It seemed to me that whether crustaceans had nociception (about as close as we’re going to get to “pain” scientifically for invertebrates in the near future) was an empirical question that should have a reasonably straightforward, factual answer.

To be continued...

^* And that’s one of those moments where you go, “Wow, has it really been more than 20 years?”

Reference

Puri S, Faulkes Z. 2010. Do decapod crustaceans have nociceptors for extreme pH? PLoS ONE 5(4): e10244. DOI: 10.1371/journal.pone.0010244