Spiny spider crab caught in the act of releasing newly hatched larvae
Fertilised eggs are kept by the female crab on her abdomen under the tail flap and are held in place with a sticky material. Here eggs are protected during the embryonic development. When fully developed, the hatched larvae are released into the water where they float with water currents.
The Red Spotted Shamecrab (calappa granulata) is a genus of crabs known commonly as box crabs in reference to their distinctly bulky exoskeleton. This crab is not very active and can spend several days burrowed in the sand with just its upper part of the carapace, eyes and antennae showing, making it difficult to spot.
As the hermit crab grows in size, it must find a larger shell and abandon the previous one.
Several hermit crab species have been observed forming a vacancy chain to exchange shells. When an individual crab finds a new empty shell it will leave its own shell and inspect the vacant shell for size. If the shell is found to be too large, the crab goes back to its own shell and then waits by the vacant shell for up to 8 hours. As new crabs arrive they also inspect the shell and, if it is too big, wait with the others, forming a group of up to 20 individuals, holding onto each other in a line from the largest to the smallest crab. As soon as a crab arrives that is the right size for the vacant shell and claims it, leaving its old shell vacant, then all the crabs in the queue swiftly exchange shells in sequence, each one moving up to the next size.
Hermit crabs can amputate their own eye stalks
Hermit crabs are are nocturnal and are at their happiest in dim lighting. They have evolved a superior night vision and their sensitivity to dim light is thousands of times sharper than that of humans.
These animals need at least 12 hours of darkness a day and if this is not available, they will initially hide either in their shell or under the sand. If the hermit crab is too overwhelmed by light to come out to eat, they can sever their eyestalks and are able to survive using their antennas and tiny hairs on their legs for sensory stimulation.
Their eyestalks may or may not grow them back while moulting, depending on the extent of the damage to any nerves. Even if the eyestalks do grow back, they may not contain working eyes.
