Sponge Crab – By Jonathan Broadbent TG4: 1/100, F18, ISO200

Sponge Crabs are a shallow water species of crustaceans. They live in a cavity which they create on the underside of their host sponge. They cut out a fragment from the sponge and trim it to their own shape using their claws. Their last two pairs of legs are shorter than the other legs and bend upward over their shell, to hold the sponge in place. The sponge grows along with the crab, providing a consistent shelter – and protection. Because they are almost completely concealed by the sponge, they can be tricky to spot. The best time for finding this species is during night dives when they are most active.

Hairy Red Hermit Crab by Marc Broadbent DSC-RX100M4: 1/40. F4, ISO100

The Hairy Red Hermit Crab has adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an asymmetric abdomen concealed by a snug-fitting shell. Hermit crabs must occupy shelter produced by other organisms, or risk being defenceless. Most species have long, spirally curved abdomens, which are soft, unlike the hard, calcified abdomens seen in related crustaceans. Most frequently, hermit crabs use the shells of sea snails. Most hermit crabs are nocturnal.