If you have ever seen a Sally Light-Foot Crab, Graspus graspus, you may have thought that it was the prettiest crab that you have ever laid eyes on. With vibrant orange on top and a sky blue underneath, this crab can be found scurrying along piers and shorelines, and traversing the black volcanic rock that is found along the coast of many islands in The Galapagos Islands.
Now, if you have spent a little more time looking, you might see another crab, usually smaller, but this one is almost pitch black, with orange spots speckling its body. What might surprise you, is this is also a Sally Light-Foot Crab, however, it is a young one, or juvenile.
So why are they different colors? Well, the younger crabs hatch a dark black color, which helps them to camoflauge almost perfectly into the volcanic rock while they are small and vulnerable to predators. Then as they get older, they get brighter. Crabs, like many invertebrates, grow by molting – which means they shed their exoskeleton, climb out, and a larger one hardens around them. Every time a Sally Light-Foot Crab molts, it gets more and more orange spots, until it loses the black all together – turning into a “sexier” adult that will be able to attract mates.
The Galapagos Islands offer amazing opportunities to encounter wildlife like this, up close, but in a responsible manner, in their own natural habitat, and to learn about and gain appreciation for all different kinds of wildlife.