Episode 173 – Bluestreak Cleaner Wrasse: The King of Cleaners

“…and today we’re talking about a fish that enjoys working at the carwash. More on that later.”

When you run a lucrative maritime cleaning service, you gotta protect your turf. The dominant bluestreak cleaner wrasse defends its territory, its business, and its family on a daily basis. But when the don disappears, it’s up to one of his leading ladies to fill his shoes. But being willing to fill any role is part of surviving here in Life, Death, and Taxonomy.


The bluestreak cleaner wrasse is a small fish with a long body shape that’s sort of like an arrow head. It has a pointed snout that widens at its midsection before tapering slightly and then opening back up to a palm shaped tail. 

Bluestreaks have an interesting coloration with light blue backs, and a dark blue stripe that starts at the nose and runs past its eyes all the way to its tail. It’s belly is white for that coveted countershaded look all the animals are into.

Younger fish are black with a blue line. 

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words Measure Up into ldtaxonomy at gmail dot com. We don’t have a new Measure Up intro this week.

  1. Goana (monitor lizard)
  2. Komodo dragon
  3. Shoebill stork
  4. Arabian Wildcat


  • 10 cm long (14 cm max)
  • How many of the diameter of the world’s smallest gold coin go into the length of the bluestreak?
  • Hint: The coin was minted by the Swissmint and it’s worth about one fourth of a franc ($0.26 USD). It features the image of the famous Albert Einstein with his tongue out photo. 
  • 47.2 coins. The coin is 2.96-millimeter (0.12-inches) 

Diving depth

  • 90 m (300 ft)
  • How many bluestreak depths go into the length of the largest valley in the solar system?
  • Hint: The valley is Valles Marineris on Mars and it’s longer than the width of the U.S. mainland. You can see it from space, maybe even with a really great telescope. 
  • 43,744 fish depths. The valley is 4000 km (2500 mi) long.

Fast Facts

The wrasse is a reef fish that’s found in the waters of the Indian and Pacific Oceans and off the coast of the islands of Oceania.

They’re in a group called cleaner fish because they like to operate cleaning stations, which are essentially reefside car washes for fish. And that’s not the weirdest part about it. Cleaning stations are areas that fish somehow know they can come to to get parasites removed.

The wrasse will greet customers by twerking. Literally, fishbase.com says, “An unfamiliar visitor is usually greeted by dance-like movements with the tail maneuvering the back part of the body up and down.” Young fish that don’t know no better will greet divers this way when they get close.

This movement and their telltale stripe help larger fish identify them as cleaners and not potential food. Other fish, like blenny, mimic the cleaners and use the deception to get close enough to bigger fish to tear chucks out of them. 

Bluestreaks can pass our tried and true self-aware test. To test animal intelligence and whether or not they’re self-aware, we put a smudge of something on an animal’s face and show them to a mirror. No, it’s not a funny prank on nature. We want to know if they think the animal in the mirror is another of their species or a reflection of themselves. 

The idea is that if you recognize yourself in a mirror, you are aware that you exist as a separate entity from the world around you. So if the animal points and laughs at the idiot with the smudge on its face, they aren’t self aware. But if they indicate that they know that the judge is on their face, they know it’s a reflection of themselves. Dogs, cats, and gorillas all fail this test. But elephants, dolphins, and maybe the wrasse pass

Stuff like this is interesting, but it also calls the test into question. Does self-recognition mean you’re self-aware? Does recognizing a reflection have other benefits that some animals need and others don’t? 

Major Fact: The Dutchman Must Always Have a Captain

Blues are extremely territorial and work in groups of females (or harems) with a dominant male leading and defending them. In order to be dominant, you simply have to be the biggest. 

However, if Jones be slain, he who slays him must take his place.

Meaning if the dominant male dies or leaves, the second largest member of the group takes his place as the new dominant male. But since all the other members of the group are females, then it falls on the largest female to take over. But that doesn’t just include acting like the dominant male – it involves becoming the dominant male. The largest female in the group will change sex in order to fulfill the role of dominant male.

The process takes about two weeks, but the promoted female will often start the male courtship display and the smaller females will start showing the female courtship display to the new leader within an hour of the dominant male disappearing. So there is often a few weeks of impotent spawning behavior while the largest female undergoes the change from female to male.

But it doesn’t stop there. Females from high-density populations will make sojourns into other harems – presumably checking out the social situation to see if there’s room at the top. Better to be a big fish in a little pond.

In a 2001 study, half of the females that spent time in other harems eventually transferred over to improve their social status and become the dominant male once the position opened up.

However, the females that transfer are less fertile than the ones that stay in their harem.

Ending: So provide a mutually-beneficial marine service, take care of your clients, and become part of the crew, part of the ship like the bluestreak cleaner wrasse here in LDT.