Species: Labroides dimidiatus

Habitat: laying down the law on coral reefs throughout the Indo-Pacific

If someone has committed a serious crime, most people agree that they should be punished more harshly than if they had committed only a minor misdemeanour. That way, people will be deterred from doing anything really heinous, like molesting children or talking at the theatre.

But this idea that the punishment should fit the crime isn't universal. Humans practise it, and some other animals also punish their fellows for bad behaviour, but until now none has ever been seen systematically varying the severity of the punishment.

Now it turns out that one animal does punish just like a human: the bluestreak cleaner wrasse. But their carefully nuanced punishment of "cheats" is really an elaborate plot to oppress their females.

Reef salon

These tropical fish are one of many species of cleaner fish that remove parasites such as lice from much larger fish. The clients get a valuable service and the cleaner fish get food. Local fish may visit the cleaners every day, and even wide-ranging beasts like sharks will occasionally drop in.

Bluestreak cleaner wrasse have small home territories called cleaning stations. Each male maintains a harem of around 16 females dotted around his territory, who help him service his clients.

These clients recognise cleaner wrasse by their small size and the blue stripe running along their sides. The cleaner wrasse stroke their clients to cement the relationship and ensure that they don't attack them.

Mmmm, mucus

But the wrasse have a serious conflict of interest. Although they will eat parasites off their clients, they actually prefer to eat the clients' mucus. As a result, they are tempted to take a bite out of the client – despite the risk of losing its custom, or even being attacked.

Nichola Raihani of the ZSL Institute of Zoology in London and colleagues reported last year that male bluestreaks punish their females if they bite a client. Deprived of future foraging opportunities, the males chase the females around and try to bite them. In response, the females refrain from further misbehaviour.

Raihani has now found that the males chase offending females for longer when their crime is more serious. She presented captive pairs with artificial "clients" – actually plexiglas plates – that carried two pieces of prawn, which the wrasse love, and either four or eight fish flakes, which they don't like as much. If either fish ate the prawn the plate was taken away, but they could eat as much fish flake as they pleased.

When the female ate a piece of prawn from a plate that had eight fish flakes – thereby depriving the pair of all those fish flakes – the male chased her more than if the plate had only four fish flakes. When a second eight-fish-flake plate was offered, females who had experienced this severe punishment were less likely to eat the prawn.

"Harsher punishment makes them cooperate more," Raihani says. The males must somehow be judging the seriousness of the females' crimes and punishing accordingly, something no other non-human animal has ever been seen doing.

The system may sound just, but it is actually systematic sexual oppression.

Feminism for fish

All bluestreak cleaner wrasse are born female. The largest individual in a given area changes into a male and dominates the remaining females.

That means each male is under constant threat from his attendant females. If one of them manages to grow bigger than him, she can change sex in just two days and potentially take over his territory.

For a female to grow bigger than her male, she needs to eat more than him. So taking chunks out of client fish could work well for her: she gets a particularly nutritious meal, but her partner gets nothing because the client fish leaves in disgust.

Accordingly, Raihani found that males were more likely to dole out harsh punishments if their partners were a similar size to them. Such large females would have been on the cusp of changing sex, so the males controlled their behaviour more strictly.

For bluestreak cleaner wrasse, fish mucus – the illicit eating thereof – is a feminist issue.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2011.0690

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Busaiku said:

So the largest one becomes a male?
This is crazy.

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thefit said:

Works the same way in a jail cell. :*(

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MetalAlien said:

I was about to hit reply... damn you. Also I bet I am bigger than you.. 6'4" 280lbs.

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LaserBuddha said:

This fish is like, literally a pimp. It's actually true, not a stupid joke like it always is. Wow.

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thefit said:

Mmm you can nibble on my mucus anytime big boy!

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All bluestreak cleaner wrasse are born female. The largest individual in a given area changes into a male and dominates the remaining females.

That means each male is under constant threat from his attendant females. If one of them manages to grow bigger than him, she can change sex in just two days and potentially take over his territory.

For a female to grow bigger than her male, she needs to eat more than him. So taking chunks out of client fish could work well for her: she gets a particularly nutritious meal, but her partner gets nothing because the client fish leaves in disgust.

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Cryptozoologist said:

The biggest female changes into a male.

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a Master Ninja said:

I don't understand how this happens. I need Mr. DNA to explain this shit to me.

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thefit said:

Works the same way in a jail cell. :*(

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a Master Ninja said:

I don't understand how this happens. I need Mr. DNA to explain this shit to me.

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thefit said:

Didn't you pay any attention during Jurassic Park?

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Gaborn said:

If you think THAT's odd, clownfish (like in Finding Nemo) are the opposite. All clownfish are born male and can become female.

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dyls said:

Is Wrasse Brady gonna have to choke a bitch?

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trinest said:

So in the sequel Nemo is a girl?

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Kaako said:

This was an awesome read. Thanks for posting.

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Obsessed said:

How exactly does the "bigger one becomes male" thing work? Like what are the chemical/hormonal changes involved?

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Obsessed said:

How exactly does the "bigger one becomes male" thing work? Like what are the chemical/hormonal changes involved?

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Korey said:

This is fucking amazing.

So this is all programmed through instinct?

Can fish count?

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Gaborn said:

As near as I can tell scientists aren't really sure how it happens with animals, we just know that it DOES happen.

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Korey said:

So this is all programmed through instinct?

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xbhaskarx said:

This is like game theory for fish...

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Fish Market: Competition gets clients better treatment from cleaner fish

Game theory models based on repeated interactions between two individuals have often been the framework for understanding cooperative interactions in humans, but these models rarely apply in nature. Non-human animals, after all, rarely find themselves in situations like the “prisoner’s dilemma.”

Instead, partner choice and competition are emerging as the framework for understanding cooperation in the natural world. Some mutualisms (biological interactions between organisms where each individual derives a fitness benefit) can be described as “biological markets,” where organisms exchange goods or services. These markets and the animals that participate in them share some similarities with humans and our markets: animals preferentially interact with partners that provide the highest-quality goods or services; animals sometimes cheat each other; competition is often a good thing, and threatening to take your business elsewhere can lead to more cooperative behavior from your partner.

In many cleaner mutualisms among fish, cleaner fish occupy cleaner “stations” where they remove parasites from cooperating client fish. Buyer beware, though, because clients often have to wait for service from a cleaner and when it’s finally their turn, they may be cheated by cleaners that feed on tissue or mucous instead of parasites. Clients don’t have many options for ensuring good service. They can’t demand their mucous back or complain to management. What they can do is go get cleaned somewhere else.

Thomas C. Adam, a graduate student at the Department of Ecology, Evolution, and Marine Biology at the University of California, Santa Barbara, investigated cleaner-client interactions involving the territorial butterflyfish Chaetodon ornatissimus.

The results of the study indicate that not only do bluestreak cleaner wrasse compete for access to their butterflyfish clients (the amount of time cleaners had access to clients was negatively associated with the number of cleaner stations in a territory and individual butterflyfish with access to multiple cleaner stations did, indeed, shop around and were less likely to return to a cleaner station for their next cleaning than individuals with access to just one cleaner station), but the ability of butterflyfish to take their business elsewhere got them higher-quality service from cleaners. To wit, (1) the observed clients were never ignored by cleaners when they had more than one cleaner station in their territory (in contrast, five of 11 fish with a single cleaner station in their territory were observed being ignored), (2) while there was no evidence that clients with access to multiple cleaner stations were cheated less frequently than clients without access, the clients with their choice of partners were less likely to have interactions terminated early by cleaners and were inspected for significantly longer during each cleaning session.

See? The free market does work sometimes.

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Korey said:

This is fucking amazing.

So this is all programmed through instinct?

Can fish count?

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