Giant spider crabs

The giant spider crab (Jacquinotia edwardsii) can be found from the intertidal zone to 500 metres in depth, but at the Auckland Islands, they are most abundant between 20 and 40 metres. They are New Zealand’s largest crab, with males having a leg span of up to 1 metre. At the Auckland Islands, they can be found in densities of up to 10 crabs per square metre. Males forage on blue and ribbed mussels and probably other shellfish, whereas females are detritus feeders, and juveniles feed on drift algae.

Why might giant spider crabs have adapted so that females and males have different diets? Can you think of another animal where the males and females eat different diets?