Roaches, Research and Unintended Consequences: A Cautionary Tale

When performing research, what happens when you restrict a research subject’s ability to perform some function – gluing a cockroach’s mouth closed to prevent it from eating, say, or gluing a ring around one antenna so the roach can’t control it?

It’s a standard part of scientific research, most would say, to study a function in order to tease out underlying biological or chemical processes and utilities of that function. Comparing a “glued” antenna with one that functions normally could have benefits to advancing knowledge.

Unless the restricted part of the body – the roach’s antenna or mouth – has more than just one function.

Recently, we reported on an NC State study showing the types of chemicals – both environmental and personal – that roaches and other insects clean off while grooming their antennae. Unlike the teenage humans parting their hair every which way in your bathroom, though, roaches clean their antennae for an important reason – to keep their olfactory senses keen. That means maintaining the ability to find food or a suitable mate, or to avoid danger.

To keep their senses keen, American cockroaches in particular groom by grabbing an antenna with a foreleg and then placing it in their mouths, methodically cleaning every section from base to tip. (See video at top of post.) Flies and ants have similar grooming tendencies, with ants – like cockroaches – using their mouths, while flies use only their forelegs.

Better understanding of roach grooming raises difficult questions about research practices, though. Coby Schal, the lead researcher on the simple but elegant insect-grooming research, cautioned other entomologists about performing experiments on roach mouths or antennae, or other multifunctional appendages.

“We need to be careful about how we do experiments,” he said. “We’ve shown that ungroomed antennae are not as sensitive to signals – like sex pheromones – as groomed antennae. So preventing the roach from grooming – either by gluing its mouth or restricting antennae movement – makes the roach sensory deprived, or blind to its environment.

“Mostly, I’m concerned that restricting an important function can have the unintended consequence of skewing research results, which would call their validity into question.”