Pairs of cleaner fish cooperate and give better service on the coral reef
The Bluestreak cleaner wrasse (Labroides dimidiatus) helps other fish species by eating parasites from their skin. The cleaner's favourite food is, however, the nutrient-rich mucus layer that covers the client fish.
Bluestreak cleaner wrasse eat parasites that have attached themselves to the client fish – but sometimes the cleaner fish can't resist the temptation to take a bite out of the client's mucus layer.