SPS reefkeepers are familiar with coral crabs.  These crabs find shelter in the branches of Acropora, Pocillopora, Seriatopora, et al., and live, eat, and breed under the coral’s protection for their entire lives.  Most reefkeepers have seen filter-feeding anemone crabs (Neopetrolisthes ohshimai) at their LFS.  And then there’s the halimeda crab we blogged about last week. These are just a few examples of crustacean’s specialized habitat, but they’re just the tip of the iceberg.

We deliberated on whether to save the best for last, but we opted to start this article off with a bang.  Our first crab makes its home in one of the strangest (and grossest) habitats of any crustacean in this article — in the anus of sea cucumbers!  As strange as the thought of living in another animal’s anus sounds, these crabs are not the only animals to call a cuke’s sphincter their home.  Pearlfish, for example, hide inside sea cumbers for defense.  Better there than inside the belly of a predator, right?

This crab blends perfectly in the brilliantly colored carnation corals.  The crab’s body even mimics the distinctive spicules of these azoox corals.

Urchins are spike-covered mobile fortresses, so it’s not surprising a lot of crustaceans (or animals for that matter) live within the prickly confines of these echinoderms.  Take for instance the Bumblebee Shrimp:

Or these Fire Urchin hitchhikers:

Have you ever seen super tiny shrimps masquerading as microalgae?  Now you have!

And now you’ve seen two species (this time in red).

Here is a hairy squat lobster who finds shelter in Giant Barrel Sponges. These massive sponges are predominantly orange or purple, so this color-coordinated lobster (with purple carapace and orange “hair”) will have no problem blending into either wall colors.

We’re not sure if this qualifies as camouflage or specialized habitat, but footage of these boxing (AKA pom pom) crabs are too awesome not to share.  Three cheers for coral reef crustaceans!

With all the niche habitats crustaceans fill using clever camouflage, who knows?  You might have some fascinating crabs and shrimps in your aquarium you never knew about!  But please don’t poke around your cuke’s rear end to find them.