The seas are full of intelligent creatures. From chatty dolphins to problem-solving octopi to tool-using tuskfish, it seems that you can hardly swim anywhere without bumping into a brainy aquatic inhabitant or two. But perhaps the most surprising development in the search for underwater intelligence is that despite having brains that weigh less than a tenth of a gram, cleaner wrasses make remarkably clever decisions and can even outperform chimpanzees and orang-utans in some experiments.

In a test where both primates and fish were presented with a choice between two meals — one permanent, one temporary — the hungry apes usually chose a meal at random and failed to learn that they should pick the food that could be taken away at any moment. Bluestreak wrasses, however, quickly cottoned on that they should always eat from the temporary food first before switching to the permanent second course.

Bluestreak wrasses also display impressive smarts when it comes to enticing new customers, as they often perform for potential clients by massaging their current clients with flutters of their fins. The massages relax their customers, and relaxed customers serve as the perfect advertisement to other fish that the wrasse provides top service.  By going the extra mile, the cleaner ensures a steady supply of clients and food.

Scientists are still unsure just how the wrasse manages to deliver so much intelligence from such a tiny brain, but it’s reassuring to know that in the seas as well as on land, the little guys can always beat the big guys thanks to a bit of smarts.