The Spider Decorator Crab (Camposcia retusa) is also known as the Blunt Decorator Crab, the Velcro Crab and the Tarantula Crab. Being well camouflaged they are difficult to spot and are probably easier found at night when their eyes reflect light back. Even then one has to look really carefully to find them.
They are decapod crustaceans in the Superfamily Majoidea, in the Inachidae family, they were first described by Latreille in 1829 with the type locality being in the Red Sea. There is only one species in this genus.
Because they are so well camouflaged and with the camouflage varying greatly depending on location, the Spider decorator crab are not easy to physically describe. Perhaps their common name of the Tarantula crab is the best way of describing them.
If one is lucky enough to see them against a background that does not match their camouflage they resemble a Tarantula spider. The carapace is teardrop shaped and it and the legs are covered in short hairs which allow the crab to attach marine growth onto its body. The chelipeds are small and fine allowing them to snip off and attach growth.
The body and legs are usually covered in algae, sponges and variety of sessile marine growth. They grow to a maximum carapace width of 30 mm and with the legs can reach a width of 10 cm.
SPIDER DECORATOR CRAB IN THE WILD
The Spider Decorator Crab appears to be more active during the night but that said, they are easier to spot at night so this could account for them being seen more often at night. They are found in the sub littoral zone and we have found them on shallow offshore reefs to a depth of at least 14 meters off Dar es Salaam in Tanzania.
The Spider Decorator Crab are found across the Indo West Pacific area from the southern and east coast of Africa to Japan and Australia.
Spider Decorator Crab are assumed to feed on small crustaceans and mollusks as well as scavenging, but there is very little information on their habits or diet.
The eggs are fertilised by the male and are then carried under the body of the female. Once they hatch the larvae go through a planktonic stage before settling down and growing into their adult form.
As a rule aquarists tend to steer away from crabs in their tanks. It is probable that these crabs could do a lot of damage in an aquarium. That said some aquarists with specialized tanks do keep them.