Reef Stories
Decorators
Camouflage specialists...
Decorator & Imitator Crabs
Crab Index
Crabs
General
Carrier Crabs
Coral Crabs
Decorator Crabs
Gall Crabs
Land & Sea Crabs
Lobsters
Porcelain Crabs
Round Crabs
Swimming Crabs
This is not a group of crabs that are related, but share the ability to decorate themselves with objects from their surroundings for camouflage or protection.
Humans had the idea of velcro from a plant, but crabs were many thousands of years ahead of them! Many have microscopic hooks on their shells much like the hooks on velcro and use them to carefully attach anything from sponges and ascidians to torn pieces of clothing to their shells. This often makes them blend perfectly into the reef. They are only noticed when they move.
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Carrier Crabs
This is a functional group comprised of crabs in the Dromidae, Dorippidae, Homolidae and Ethusidae. They camouflage themselves by using their last pair of legs to hold sponges, ascidians, fire urchins, starfish, leaves, jellyfish or other objects over their backs.
Decorator Crabs
This is a pot pouri of crabs that decorate either themselves with something or crabs that look like they are decorated, e.g. the Orang-Utan Crab (Oncinopus sp.) which has long body hairs that look like algae. It's not exactly well camouflaged as it sits in Bubble Coral (Plerogyra), but presumably just looks like an algal growth to predators.
Many relatives of the Orang-Utan Crab are well hidden in the byozoans they rest on while feeding at night. Achaeus species are closely related and some can reach 10cm across. The larger species will attach bryozoan branches all over their body to break up their body pattern, while the stings of the the bryozoans again deter predators.
Spider Crabs in the Majidae provide some of the largest and most commonly seem decorator crabs. The Corallimorph Decorator Crab (Cyclocoeloma tuberculata) looks like a space-age monster as it walks semi-upright through the reef covered in corallimorph anenomes. The eyes protrude out through the anenomes and from the front the ever moving mouthparts and knobbly legs would give you nightmares if you were 3cm high!
The Blunt Decorator Crab (Camposcia retusa) is another large crab that slowly moves over the reef at night. It is often very colourful, taking a variety of different coloured sponges, a mixture of ascidians and the odd piece of seaweed. I found one specimen that had even attached torn pieces of blue underpants to it's carapace. It certainly did not look like a crab at first glance!
Imitator Crabs
These crabs belong to the Epialtidae. Their body bears a resemblance to algae (e.g. Halimeda), soft coral, sea whips or the gorgonians they live on. The type of camouflage is similar to that used by ovulid cowries. Some of these crabs e.g. Huenia, Hoplophrys (the Broccoli Crab) attach pieces of algae, or soft coral to their bodies as additional camouflage.
Twin-Spined Crabs
These crabs are in the familiy Pisidae. They have two long spines on their heads. Often, pieces of hydroid, algae or sponge will be impaled on these spines. Some species, e.g. Hyastenus tabolongi attach colonial zoanthid polyps over every part of their body, so even if they move, they are difficult to see. Others like H. bispinosus attach an intensely stinging hydroid to not just the spines, but to theire body and legs. Presumably the stinging hydroid is effective at deterring predators.
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Carrier Crabs
Carrier Crabs
This is a functional group comprised of crabs in the Dromidae, Dorippidae, Homolidae and Ethusidae. They camouflage themselves by using their last pair of legs to hold sponges, ascidians, fire urchins, starfish, leaves, jellyfish or other objects over their backs.
Decorator Crabs
Decorator Crabs
This is a pot pouri of crabs that decorate either themselves with something or crabs that look like they are decorated, e.g. the Orang-Utan Crab (Oncinopus sp.) which has long body hairs that look like algae. It's not exactly well camouflaged as it sits in Bubble Coral (Plerogyra), but presumably just looks like an algal growth to predators.
Many relatives of the Orang-Utan Crab are well hidden in the byozoans they rest on while feeding at night. Achaeus species are closely related and some can reach 10cm across. The larger species will attach bryozoan branches all over their body to break up their body pattern, while the stings of the the bryozoans again deter predators.
Spider Crabs in the Majidae provide some of the largest and most commonly seem decorator crabs. The Corallimorph Decorator Crab (Cyclocoeloma tuberculata) looks like a space-age monster as it walks semi-upright through the reef covered in corallimorph anenomes. The eyes protrude out through the anenomes and from the front the ever moving mouthparts and knobbly legs would give you nightmares if you were 3cm high!
The Blunt Decorator Crab (Camposcia retusa) is another large crab that slowly moves over the reef at night. It is often very colourful, taking a variety of different coloured sponges, a mixture of ascidians and the odd piece of seaweed. I found one specimen that had even attached torn pieces of blue underpants to it's carapace. It certainly did not look like a crab at first glance!
Imitator Crabs
Imitator Crabs
These crabs belong to the Epialtidae. Their body bears a resemblance to algae (e.g. Halimeda), soft coral, sea whips or the gorgonians they live on. The type of camouflage is similar to that used by ovulid cowries. Some of these crabs e.g. Huenia, Hoplophrys (the Broccoli Crab) attach pieces of algae, or soft coral to their bodies as additional camouflage.
Twin-Spined Crabs
Twin-Spined Crabs
These crabs are in the familiy Pisidae. They have two long spines on their heads. Often, pieces of hydroid, algae or sponge will be impaled on these spines. Some species, e.g. Hyastenus tabolongi attach colonial zoanthid polyps over every part of their body, so even if they move, they are difficult to see. Others like H. bispinosus attach an intensely stinging hydroid to not just the spines, but to theire body and legs. Presumably the stinging hydroid is effective at deterring predators.
