Talking Up a Bluestreak
A few words for one smart little fish
Delia recognized the lemon damselfish hesitating at the edge of the cleaning station. There were hundreds of the little yellow fish around her patch of the reef, but as this one cautiously peeked out around the edge of the coral she gave Delia a glimpse of her unique ultra violet facial pattern. It was the same fish Delia had nipped a few hours earlier, eating a little delicious mucus and a healthy scale off the damsel instead of sticking to the gentle exfoliation and parasite removal service that a visit to the cleaner wrasses was meant to provide. It had been wrong, Delia knew, to betray the damsel's trust like that. The bold black stripe running along Delia's vibrant blue and yellow side was supposed to be a sign of quality; she was a true bluestreak after all, not some imposter like those fangblennys who hung around the station hoping to sneak in a quick bite of fish flesh. But it had been the damsel's third visit to Delia's station that morning. No bigger than Delia herself, none of the damselfish offered up much of a meal on their first visit of the day, never mind on their third. Without a parasite in sight, what else was Delia supposed to eat but a little of the client themselves?
But try explaining that to this timid damselfish. No, the only way to win back the trust of one of her regulars was to apologize. As soon as the yellow face peeked out again, Delia started her dance. She waggled and flicked her tail, lilting back and forth through the water in view of the damsel. Delia got a little closer with each pass, every time expecting the damsel to swim out and strike the pose showing she was ready to be cleaned. But Delia kept dancing and dancing, and the damsel only watched. Delia wanted to give up and move on, but now other fish were watching, including some of the other wrasses. Delia was losing status by the second. She knew this damsel was particularly fearful, but there was no reason for the other fish to know that, or to read this situation as anything other than a failure on Delia's part.
She turned it up a notch, and swam right up to lightly brush the damsel with her fins and tail. Then a little more dancing, a little more massaging, and finally the damsel was back on board. The yellow fish swam out fully from behind the coral and stopped, ready for another cleaning.
Relieved, Delia was about to go to work looking for any small blemish she could have missed earlier. It would be a lot of energy spent for a tiny reward, but keeping up her reputation was worth it.
At least, that's what she was thinking until the large shadow fell over them both. A grouper who dwarfed the wrasse and damselfish alike had pulled up to the cleaning station just above them. Delia had never seen the grouper before, and knew it wouldn't stay long. She could also see that it was covered in larvae and dead skin; a beautiful but temporary buffet. The other wrasse from the station were already flocking to the grouper's sides. If Delia left the damselfish now she could lose her regular client forever. But what was one damselfish in the grand scheme of things? There were always more fish in the sea.
Delia darted up to grouper and started frantically flitting from morsel to morsel. The other wrasses had already claimed the best spots, so Delia was left with the more dangerous areas around the grouper's head and mouth. There was meant to be an understanding among predators that cleaner fish were not for eating, but with a new, strange fish it was always a gamble. This one also smelled of hunger, which made the danger greater.
Delia was working on the grouper's gills when she saw his eye move. She darted back to do a little reassuring dance and remind the grouper that they were all there to serve him. But after putting a little space between herself and the predator, Delia could tell he hadn't been thinking about her at all. The lemon damselfish, thoroughly entranced by Delia's massage, still hung in the water out in the open. The grouper's posture changed and the other wrasse darted to safety among the coral. Every fish knew what was about to happen. Every fish except the damsel Delia had lulled into submission.
Delia struck before the grouper could. She shot forward and nipped the grouper's gill covers once, twice, three times, as quickly as she could. She didn't have the jaws of a blenny and barely left a mark, but it was enough to make the grouper thrash, which was enough to startle the damsel into hiding.
The grouper slowly swam away, still hungry and still carrying most of his parasites. Delia didn't know if the other wrasse would be annoyed that she'd cost them a meal as well, but she didn't care. Maybe there were other fish in the sea, but this was her part of the sea, and these were her fish.
She found the terrified lemon damselfish tucked in the coral, and gently restarted her massage. Delia would remember this face and, from now on, one little lemon damselfish would always move to the front of the line.
~ Marilyn Anne Campbell
About the Bluestreak Cleaner Wrasse
When we were choosing a fish for this issue, I remembered hearing about a little tropical fish called the bluestreak cleaner wrasse (Labroides dimidiatus) who made nature-news headlines for being the first fish to potentially pass the Mirror Self-Recognition test. The mirror test has been used by researchers as an animal cognition test since the 1970s as one way to measure self-awareness.
It turns out that whether or not the wrasse really can "pass" the test has been disputed, but that's a story for another day. Suffice to say I think the controversy says a lot more about the whole mirror test concept than the wrasse experiment itself. (As in, humans like thinking we're pretty special so we try to create definitions of intelligence to prove it, which backfire when it turns out fish are special too.)
A much more interesting way to look at intelligence has to do with what abilities an animal has related to their life and environment rather than ours. That's where the bluestreak cleaner wrasse shines again. Wrasse really do:
work in pairs or groups at coral reef cleaning stations
recognize the fish who visit regularly, and remember previous interactions with them
"dance" to signal their intent, and offer massages to apologize for wrongdoings
behave differently when they know other fish are watching
strategize about which fish to prioritize based on who is likely to stick around and who represents a fleeting opportunity just passing through
The story still took some artistic liberties, of course. I didn't come across any evidence that a wrasse would act to defend another fish, or would ever offer a place "at the front of the line" based on anything other than how good of a meal each client represents.
Still, even without a touch of fiction, the fact is that bluestreak cleaner wrasse are some amazing little fish, whether they know it or not.
Want even more about the bluestreak cleaner wrasse?
Watch a cleaning station in action in Jonathan Bird’s Blue World, Season 3 Episode 7, on YouTube (9 minutes)
(Apparently in the 2004 animated movie “Shark Tale” the main fish voiced by Will Smith is a cleaner wrasse, but perhaps don’t count on that one for an accurate portrayal.)
Join the Conversation
Have you ever seen a cleaner wrasse at work, whether in the wild or in an aquarium? Know a fascinating fish fact, or catch a mistake in the story? Or what are your thoughts on animal intelligence in general? Join the conversation:
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Thanks for reading,
Marilyn & Steve
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