The cleaner fish, scientifically known as Labroides dimidiatus, has a fascinating relationship with other fish species. Its bright coloration attracts larger fish that seek relief from itching. Labroides dimidiatus has the ability to clean off parasites and other unwanted organisms from the bodies of these fish, providing them with comfort.
The interactions are quite delicate: larger, predatory fish approach carefully, avoiding any actions that might startle the cleaner fish, demonstrating their “good intentions” to receive a thorough cleaning.
While the larger fish doze, the small cleaner fish expertly swim around, nibbling continuously across the surfaces of their hosts to consume “lice” and various other parasites.
Labroides dimidiatus even swims into the deep mouths of groupers to clean their teeth. Once their mouths are clean, the larger fish will even open their gill covers to allow the cleaner fish to enter and clean their gills.
Often, fish waiting for cleaning must take turns. This mutually beneficial arrangement means larger fish enjoy cleanliness without any cost, while cleaner fish get a satisfying meal.
In areas of rocky reefs where cleaner fish are absent for some reason, the health of larger fish visibly declines due to diseases caused by parasites.
Cleaner fish also have a “business market” and know how to defend their “market share” – they monopolize clients from other fish of the same species.
Another remarkable feature of this species is that if there is a shortage of male or female fish in a population, some individuals will change sex. Eggs are laid in a nesting area and are guarded by both the male and female fish. When the eggs hatch, the fry drift among the reefs, feeding on plankton until they grow large enough to become “specialists in eradicating parasites.”
During the day, Labroides dimidiatus displays a shimmering blue color with a prominent black stripe running along its body from the mouth to the tail. At night, these fish are clever enough to hide among the rocks and even use seaweed to camouflage themselves for safety.
Labroides dimidiatus is distributed throughout the Indian and Pacific Oceans, except in the Hawaiian region.
