The living toothbrushes that keep coral reefs healthy
The most important fishes on a coral reef aren’t the impressive predatory ones or the flashy colourful ones – they’re just humble cleaners.
The cleaner fish Laborides dimidiatuscleaner fish Laborides dimidiatus is cross between a janitor and a medic. It runs special “cleaning stations”, which other fish and ocean animals visit for a regular scrub. The cleaners remove parasites from their clients, even swimming into the open jaws of predators like moray eels and groupers. They’re like living toothbrushes and scrubs. And they work hard – every day, a single cleaner inspects over two thousand clients, and some clients visit the stations more than a hundred times a day.
The cleaners, and their relationships with their clients, make a classic case study for biologists studying the evolution of cooperation. The tiny fish clearly get benefits in the form of a meal, and they enjoy a sort of diplomatic immunity from otherwise hungry hunters. On the face of it, the clients also benefit by getting scrubbed of harmful parasites. Now, Peter Waldie from the University of Queensland has shown how important this hygiene is.
Eight and a half years ago, Waldie removed all the cleaners from a few patch reefs at Lizard Island in the Great Barrier Reef. Now, these reefs have 23% fewer species than those where the cleaners are still around. And the populations of the fish that stayed around are 37% smaller.
Waldie also focused on two species that use the cleaners’ services – the lemon damselfish and the ambon damselfish. In the cleaners’ absence, these clients grew more solely, and were smaller as adults. Perhaps parasites sap energy that would otherwise be used for growth. Perhaps the damsels have to spend more time on the lookout for danger (the presence of cleaner fish tends to pacify nearby predators). Either way, this is the first time that anyone has shown that a cleaner animal affects the size of its clients, and it shows how troublesome parasites can be.
This shift in size will probably cascade through the generations, since smaller damselfishes lay fewer eggs and raise fewer young. And damselfishes don’t patronise cleaning stations very often, so more regular clients probably depend on the cleaners to an even more dramatic extent.
The absence of the cleaners could also ripple through the entire reef community. Many reef fish graze on algae that would otherwise impede the growth of corals, while others control the populations of starfish that eat corals. Fewer cleaners lead to fewer fish, which could mean weaker reefs.
These a remarkable changes, when you consider that the cleaners are small and relatively rare. So far, scientists have looked at what happens to coral reefs when you remove common reef fish or big predators through overfishing. These studies clearly show that such removals can change the surrounding reef communities, but Waldie has found that displacing this single species of tiny cleaners has the same effect as massive overfishing.
Waldie writes, “The large-scale effect of the presence of the relatively small and uncommon fish, Labroides dimidiadus, on other fishes is unparalleled on coral reefs.” He recommends that conservationists pay more attention to this unassuming fish, especially since it is one of the top ten most exported aquarium fish to the USA and the UK.
Reference: Waldie, Blomberg, Cheney, Goldizen & Grutter. 2011. Long-Term Effects of the Cleaner Fish Labroides dimidiatus on Coral Reef Fish Communities. PLoS ONE http://dx.doi.org/10.1371/journal.pone.0021201
More on cleaner fish:
Go Further
Animals
- Octopuses have a lot of secrets. Can you guess 8 of them?
- Animals
- Feature
Octopuses have a lot of secrets. Can you guess 8 of them? - This biologist and her rescue dog help protect bears in the AndesThis biologist and her rescue dog help protect bears in the Andes
- An octopus invited this writer into her tank—and her secret worldAn octopus invited this writer into her tank—and her secret world
- Peace-loving bonobos are more aggressive than we thoughtPeace-loving bonobos are more aggressive than we thought
Environment
- Listen to 30 years of climate change transformed into haunting musicListen to 30 years of climate change transformed into haunting music
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- U.S. plans to clean its drinking water. What does that mean?U.S. plans to clean its drinking water. What does that mean?
- Food systems: supporting the triangle of food security, Video Story
- Paid Content
Food systems: supporting the triangle of food security - Will we ever solve the mystery of the Mima mounds?Will we ever solve the mystery of the Mima mounds?
History & Culture
- Strange clues in a Maya temple reveal a fiery political dramaStrange clues in a Maya temple reveal a fiery political drama
- How technology is revealing secrets in these ancient scrollsHow technology is revealing secrets in these ancient scrolls
- Pilgrimages aren’t just spiritual anymore. They’re a workout.Pilgrimages aren’t just spiritual anymore. They’re a workout.
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- This ancient cure was just revived in a lab. Does it work?This ancient cure was just revived in a lab. Does it work?
Science
- The unexpected health benefits of Ozempic and MounjaroThe unexpected health benefits of Ozempic and Mounjaro
- Do you have an inner monologue? Here’s what it reveals about you.Do you have an inner monologue? Here’s what it reveals about you.
- Jupiter’s volcanic moon Io has been erupting for billions of yearsJupiter’s volcanic moon Io has been erupting for billions of years
- This 80-foot-long sea monster was the killer whale of its timeThis 80-foot-long sea monster was the killer whale of its time
Travel
- How nanobreweries are shaking up Portland's beer sceneHow nanobreweries are shaking up Portland's beer scene
- How to plan an epic summer trip to a national parkHow to plan an epic summer trip to a national park
- This town is the Alps' first European Capital of CultureThis town is the Alps' first European Capital of Culture
- This royal city lies in the shadow of Kuala LumpurThis royal city lies in the shadow of Kuala Lumpur