File:Caribbean Hermit Crab Changing Shells.webm

English: This video shows a captive Coenobita clypeatus - Caribbean hermit crab - inspecting and moving its abdomen from a lightning whelk shell into a common whelk shell. Hermit crabs are rarely witnessed changing shells, in or out of captivity, as it is a moment of physical vulnerability for the crustacean. In the beginning of the video, only the front of the crab's cephalothorax and first three pereiopod pairs are visible. The crab examines the common whelk shell, primarily with its antennules, before feeling deeper in with the left members of its two foremost pairs of pereiopods. The right members of the two foremost pairs of pereiopods are used for stabilization, as are the third pair. With this analysis, the crab finds that the shell is empty, clean, and strong: a suitable home. The crab rotates the shell to a convenient angle, then stabilizes the shell by moving its chelipeds into the shell's aperture and holding onto the outside with its second and pereiopod pair. Slowly and gently, the crab pushes with its left third pereiopod and extracts itself from the lightning whelk shell. As more of its cephalothorax becomes visible, note the vertical stripes on its side - the crab’s gills lay beneath this section of shell. The fourth and fifth pairs of pereiopods - the non-walking pairs, which stabilize the abdomen within the shell - become visible as the crab pulls itself further out, then the crab’s abdomen is finally revealed. It is soft and white-spotted, with flexible plating where it connects to the cephalothorax on the dorsal side. At the end of the abdomen, mostly hidden by the crab’s body as it swings itself over, is the waste-expelling telson, flanked by two anchoring uropods. The crab is suspended for just a moment, then it lowers itself into the common whelk shell and makes sure the fit is snug with its fourth and fifth pereiopod pairs.