5 min read

We Thought They Were Just One Animal. We Were Wrong.

<p>Flickr/Arthur Anker</p>

At first glance, these may look like individual animals - but don't be fooled! Meet seven critter couples working thisclose together.

1. False clown anemonefish and cymothoa

(fotonatura.org/Gustavo Maqueda Batanero)

This adorable false clown anemonefish is hiding an equally cute crustacean called Cymothoa exigua in its mouth. Cymothoa can be found in a wide range of fish species, including perch and bass. The crustacean obtains nutrients by sucking blood from the tongue of its host, and although it's exact behavior is still a mystery, Cymothoa helps the fish to break down food. The little crustacean actually acts like a second tongue.

2. Nudibranch

(Flickr/scott gietler)

The nudibranch is made up of body parts from two different animals. It steals the stinging cells from the Portuguese man-of-war and integrates them into its own body. This adorable mollusk would be considered the Frankenstein of the animal world, if not for its uncanny resemblance to a light-up plush toy.

3. Pearlfish and sea cucumber

(Flickr/Tourism Queenland)

Together, the pearlfish and sea cucumber resemble some kind of a loaf, perhaps with asparagus sticking out. That's the pearlfish, which resides in the anal cavity of the sea cucumber to stay safe from predators. Although hiding from predators inside a sea cucumber presents an obvious benefit for a pearlfish, it isn't known whether the sea cucumber benefits from this relationship. Either way, the pearlfish usually isn't alone in there; a sea cucumber can actually house several fish at a time!

4. Portuguese man-of-war


The Portuguese man-of-war isn't a single animal, but rather a colony of polyps that make up specialized sections of its body. Its tentacles can be as long as 165 feet.

5. Hydra

(Flickr/Carolina Biological Supply Company)

The hydra reproduces asexually by having its offspring "bud off" from its body. What might look like a specialized tentacle on the side of a hydra may actually be hydra junior waiting to leave the house.

6. Sloth and moth

(Flickr/Arthur Anker)

The cuddly ball of fuzz that we know as the sloth actually carries a few housemates under its fur - tiny moths that help digest the animal's feces.

7. Anglerfish


The male and female anglerfish make the best and worst animal couple. When the male encounters a female, he bites into her and fuses with her body until most of his organs either disappear or lose their function. Because misery loves company, the female can accommodate six (or more!) males on her body. This interesting adaptation has taken place due to the isolating conditions found near the ocean floor. A mate is so hard to come by in such a large environment that it's best if partners remain attached at the hip.