We named him Squirt – not because he was the smallest of the 16 cuttlefish in the pool, but because anyone with the audacity to scoop him into a separate tank to study him was likely to get soaked.

The algae octopus (Abdopus aculeatus), also called the prickly octopus, lives in the Indo-West Pacific. Despite its modest size — its mantle (main body) is only 3 inches long with arms stretching up ...