How a Rainbow Crab Moults Its Exoskeleton
If you have every wondered just how these crustaceans manage to climb out of their bodies then I am about to explain.
What is a crustacean?
Crustacean is the name given to a very large, diverse group of arthropods. You will know them as crabs, lobsters and the like. Basically it’s a creature with an exoskeleton.
Photograph by author. Young Rainbow crab.
What is an arthropod?
This is the word that describes an invertebrate creature with an exoskeleton and a segmented body with jointed legs.
What is an exoskeleton?
True crustaceans have what is called an exoskeleton. Basically their hard skeleton is on the outside of their flesh and organs as apposed to inside like ours. Of course as these rainbow crabs only start off very small and grow very rapidly in the first few years of life, they have to get rid of their old exoskeleton so they can grow. They will moult every few months as youngsters but this slows down to about once a year as they reach maturity, which is when they are aged around three to four years old.
The first signs of the Rainbow crab going into moult will be that he will stop all eating. They can go several months without eating, without any side effects or consequences to this voluntary starvation. They will only moult when they feel safe. As they are land crabs (which means they live on land but they still do have to go into the water to take oxygen out of the water via gills which live on the outside of their bodies) they may seek the shelter of a riverbank burrow, a large rock formation or some hidden water in the wild. If you keep one as a pet make sure he has lots of calm hiding places to choose from.
What happens to the shell?
It is not just the shell that gets a make over but the whole crab. If your crab has suffered any injury and lost a limb it will replace that limb when its new body emerges from the old skeleton.
Photograph by author. The opened shell and limbs.
Although I have never had the privilege to witness my crab actually emerging from his old skeleton I have seen him a few minuets later, just after he has come out.
It is a very stressful time for a crab because when he emerges his body is soft; he has no protection at all until his exoskeleton hardens which can take a couple of days. You must never disturb them in the middle of moult it could kill them.
Photograph by author. The new shell and limbs are still soft.
First of all, the shell brakes open around the middle. Just like an Easter egg to reveal the goodies inside! This enables him to then pull all his limbs free from his old skeleton casings and squeeze his body out. The hairs on the limbs are left still protruding from the old discarded skeleton, the only thing that doesn’t get renewed are his stalk eyes because they obviously just poke through the skeleton and are not actually part of it. I leave the old skeleton in with the crab so he can eat it and replace lost calcium.
Photograph by author. He hides behind his rock.
I find this a truly amazing happening and will never get board of seeing the new out come each time he moults. I hope you enjoy the photographs of my Rainbow crab Rufus.
Photograph by author. He has now ready to start eating again. Ham or cucumber?
Photograph by author. Colours all back to normal now his shell is hard.