These Tiny Fish Live In the Bumholes Of Sea Cucumbers
Home is where the heart is - or, in this case, where the bum is.
Meet the pearlfish, a pencil-thin swimmer found off the coast of nearly every Australian state; like other members of the Carapidae family, it enjoys nothing more than finding a body cavity to set up shop in.
But one particular species' abode of choice is in the anus of a sea cucumber which, Australian Geographic explains, it locates by "following the current of water as it's inhaled and expelled".
Then it gives the area a little tap - knock knock, anyone home kind of thing - before "penetrating" the sea cucumber.
It uses one of two techniques:
1. Head-first, propelling itself by "violently thrusting its tail from side to side" or;
2. Tail-first, lining up and sliding in with the cucumber's next "breath".
They're usually pretty solitary fish but, on occasion, they have been known to welcome a partner into the fold. Ahem.
Check out the full video above, a snippet from BBC's Natural World series, and just think about how much you'd save on heating.