I love carry crabs! These little crabs of the family Dorippidae, have modified back legs that they use to grip things, living or inanimate, to disguise themselves. Last month, I posted video of one that I saw years ago, stumbling around with a live, writhing nudibranch. In 1999, on a night dive in Lembeh Strait Indonesia, I saw a tissue box run across the sand. I knew nothing about “carry” crabs at the time but laughed out loud when our dive guide gingerly tipped the box over to reveal a small crab clinging to the squared off edge. As soon as the box was released, it wobbled off, under crab power, into the darkness.
While we’ve been mighty amused at the sight of a moving banana peel or a tipsy nudibranch, this is serious business to these crabs that depend on camouflage to avoid predators. We usually see them moving about at night so I wonder how many animals or pieces of debris we’ve passed by during the day that were serving as cover for one of these crabs?
Two of my favorite sightings are a tiny crab that was totally overpowered by the jellyfish it was carrying – begging the question of who was carrying whom and the other was the crab at the beginning of this post, that had pulled a sea pen, a soft coral of the order Pennatulacea, from the bottom. Sea Pens are sessile animals that anchor themselves into the substrate with a fleshy peduncle. I knew something was amiss when I saw the entire animal exposed and lying on its side in the open sand. I paused and watched for about a minute and sure enough it started walking sideways – imagine that!