Cleaning mutualism on the reef: It’s a Hip-Hop World!


Dr. Simon Gingins

This month’s guestblog is by Dr. Simon Gingins, who currently does research on damselfish at the department of Collective Behaviour in the Max Planck Institute, in Konstanz (Germany). Simon and I met a few years ago at the Lizard Island Research Station, where he was doing research on the behaviour of cleaner wrasses. His blog describes some of his cleaner wrasse research….and hiphop. Besides being a good researcher, Simon is also a great photographer, so make sure to have a look at his site.


An anthias gets cleaned by a bluestreak cleaner wrasse

I know this is old school, but do you remember Eminem’s song Lose yourself? Well, to my big surprise, I recently realized that the lyrics fit very well with the ecology of cleaners. Let me show you by quoting the relevant parts of this song throughout the text. But first, let me start with the beginning. What is cleaning? Cleaning is a behaviour that implies the removal of parasites or dead tissues off another animal. It is widespread, particularly on coral reefs. Many species engage in cleaning, including shrimps and crabs, but it is mostly performed by fishes, as diverse as surgeonfishes, triggerfishes, jacks, butterflyfishes, gobies, and many more. Most fishes only clean occasionally, mainly as juveniles, and get most of their food by other means. However, a handful of species are “professional cleaners” and get all of their food through cleaning. Here, I will focus on the most studied of these species, the bluestreak cleaner wrasse Labroides dimidiatus. This species can have more than 2000 cleaning sessions per day, and client fishes actively visit their territories, called “cleaning stations”. They also give massages by vibrating their pectoral fins on the body of their clients, which was shown to decrease cortisol levels in client fishes. Cortisol is a proxy to measure stress, and thus this additional service is beneficial for clients as is calms them down.

So the cleaner gets a meal and the client gets its nasty parasites removed and a massage. Sound like everybody’s happy, no? Well, the situation actually gets more complicated because the cleaner wrasse prefers to bite client fishes and get a mouthful of yummy mucus, rather than focus on the parasites. Biting client fishes is cheating, but mucus appears to be like crack for cleaners. Or as Eminem puts it:

If you had, one shot, or one opportunity,
To seize everything you ever wanted. In one moment.
Would you capture it? or just let it slip?”

Well, it depends, because of course client fishes don’t visit cleaners to be exploited, and they’re not really happy when they get cheated. So how do clients respond to cheating cleaners? Imagine a client fish with a large territory. Large enough that it has access to many cleaning stations.

“He’s known as the globetrotter”

If it’s not happy with the service of one cleaner, it can just leave and look for another one. Basically, it can play the competition.

 “They moved on to the next schmoe”

This is what my ex-supervisor Redouan Bshary referred to as “big city life”: If you’re not happy with your hairdresser, just go to another one. But some client species don’t have choice options. The size of their territory is more like a village than a big city, and these fishes often have access to only one cleaning station, if any. Cleaners appear to be aware of these differences, and give priority and a better service to big city clients than to villagers. But the villagers still have one trick up their sleeve to make cleaners more cooperative: they punish. When they get cheated, they often chase the cleaner and try to bite it:

“No more games, I’m a change what you call rage”

And it was shown that the next time they meet, the cleaner will be more cooperative with the individual that punished it.


Bluestreak  cleaner wrasses cleaning a grouper

Finally, there is one category of clients with whom cleaners behave very, very nicely: predators. A predator striking at a cleaner during a cleaning interaction has never been witnessed so far. Nevertheless, it’s pretty obvious why cheating a predator might not turn out to be a good idea. To quote Eminem again, in interactions with predators:

“Success is my only m*********ing option, failure’s not!”

In summary, when a cleaner is interacting with a client, eating its preferred food has negative consequences. The client might just leave, but it might also try to punish it, or even potentially eat it. Cleaners thus came up with very strategic behaviours in order to determine who they can cheat, and when it’s best to cheat.

“I’ve got to formulate a plot or I end up in jail or shot”

As already mentioned, they vary the quality of the service they provide according to the category of clients. But it doesn’t stop there, they also adjust their behaviour depending on whether they are being observed by potential clients or not. If a client waiting to be inspected witnesses the cleaner cheating other clients, it might decide to leave and search for a more cooperative partner.

“His hoes don’t want him no more, he’s cold product”

As a result, cleaners behave more cooperatively in the presence of an audience. This ability is quite surprising for such a small fish, since thus far the only evidence that the presence of an audience increased cooperation came from humans. While humans benefit from the computing power of a large brain to take decisions, it appears that the cleaner wrasse L. dimidiatus managed to acquire quite sophisticated behaviours without a large brain. Recent evidence suggests that their exceptional performance might be limited to situations linked to cleaning, and fall short outside of their domain of expertise. It seems that the highly social nature of cleaners and the conflicts associated with it drove cleaners to acquire the skills to deal with these specific situations. But it did not select for increased brain size or some kind of general intelligence. So the next time you go on the reef, I invite you to take some time to observe cleaners and to imagine what it’s like to deal with all these clients coming and going.

“This is my life and these times are so hard”

I’d like to conclude by pointing out that for a guy who claims to have read only one book in his entire life, Eminem proved to have great insights when it comes to cooperative behaviour in fishes. And from what he confesses in another song (Without me), he considers himself an important contributor to fish conservation too:

“No matter how many fish in the sea it’d be so empty without me”

Dr. Simon Gingins


Simon during fieldwork

Postdoctoral Fellow

Department of Collective Behaviour

Max Planck Institute

Twitter: @SimonGingins


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