Most of the time when animals have funny names, it’s the common name of the animal that brings us amusement. The scientific names of animals are generally pretty boring and unintelligible. Today’s animal, the sally lightfoot crab, is an exception to this rule. Or so I thought it was. I originally read the animal’s name as “Graspus graspus” which would be a great name for a crab. About halfway through this post, I realized I had misread the name, and it is the far more boring “Grapsus grapsus”. After some quick research, I believe that grapsus comes from the Greek for crab, which means the sally lightfoot crab’s actual name means “crab crab”. So I guess it’s a little funny, but not exactly what I originally wanted.
Upadate: while going through these blog posts in 2021, I once more read their name as ‘Graspus graspus’, and was once again disappointed. It’s nice to know things don’t change.
My rambling aside, let’s talk about the actual animal! Sally lightfoot crabs are found in coastal areas in North and South America, and on islands from the Caribbean to the Galapagos. They like warmer areas, living in tropical and subtropical waters. The crabs will live in any areas with rocky shores, and usually stay at or above the spray line (the area above high tide that is usually not submerged in water).
These crabs are not particularly large, reaching between 5 to 8 cm in shell width. They are quite pretty crabs, being either bright red or yellow with fun black or green markings. Their feet are a nice cheery yellow and their claws are usually red. Young crabs are dark and blend in with the surrounding rocks.
Reproduction in sally lightfoot crabs occurs year round, with egg hatching occurring during full moons. Males compete for females by facing off with other males and doing a little “dance”. The crabs hold hands, then step left and right, presumably sizing each other up. If neither crab backs off, they will start fighting, which involves the crabs trying to break each others claws off. Sounds pretty nasty to me. Once males have won the right to mate, they deposit their sperm into females, who use what they need to fertilize their eggs and store the rest for later use.
Once their eggs are laid, females carry them on their bellies until the little crabs are ready to hatch. When the eggs are ready, female Lightfoot crabs helps them hatch by rubbing the eggs between their bodies and rough surfaces. The larvae hatch into the ocean where they swim out to deeper waters and begin to develop. Once they start looking like a crab, the young lightfoots make their way to the intertidal zone and start their adult lives. While they are still young, juvenile crabs tend to live in groups, while adult crabs are generally solitary.
Sally lightfoot crabs eat a wide variety of food, including sponges, molluscs, crustaceans, and small vertebrates. They have very strong feet which allow them to wander along the waterline looking for food without being washed away. These crabs have also been known to eat ticks off of live marine iguanas, helping the big reptiles be rid of parasites.
Although they weren’t named as wonderfully as I thought they were, I’m actually pretty impressed with sally lightfoot crabs. They are a pretty neat species.