ROY L. CALDWELL, DEPARTMENT OF INTEGRATIVE BIOLOGY, UNIVERSITY OF CALIFORNIA, BERKELEY, CALIFORNIA

Mantis shrimp brain contains memory and learning centers found only in insects

This mantis shrimp (Gonodactylus smithii) might have a much more elaborate brain than previously thought. That’s the conclusion of the first study to peer into the head of more than 200 crustaceans, including crabs, shrimp, and lobsters. Researchers discovered that the brain of mantis shrimp contains memory and learning centers, called mushroom bodies, which so far have been seen only in insects. The team also found similar structures in close relatives of these sea creatures: cleaner shrimp, pistol shrimp, and hermit crabs. This may not be a coincidence, the researchers say, because mantis shrimp and their brethren are the only crustaceans that hunt over long distances and might have to remember where to get food. But the finding, reported in eLife, is likely to stir debate: Scientists agree that mushroom bodies evolved after the insect lineage split off from the crustacean lineage about 480 million years ago; finding these learning centers in mantis shrimp means that either mushroom bodies are much more ancient than scientists realized and were lost in all crustaceans but mantis shrimp, or that these structures are similar to their counterparts in insects but have evolved independently.