A Baby Cuttlefish | Recent studies indicate that cuttlefish are among the most intelligent invertebrates. Cuttlefish also have one of the largest brain-to-body size ratios of all invertebrates. Cuttlefish, despite their name, are not fish but molluscs. They eat crabs, shrimp, fish, octopuses, worms, small molluscs, and other cuttlefish. Their predators include dolphins, sharks, fish, seals, seabirds and other cuttlefish. Their life expectancy is about one to two years.