Squid are cephalopods (the Greek term for head-footed) and belong to the same family as the nautilus, octopus and cuttlefish. They live in saltwater all over the world and range in size from 1 foot to 60 feet. Squid are important to the ecosystem as both predator and prey. Along with sharks and sperm whales, humans enjoy eating squid, often called calamari on a restaurant menu.
The squid is an invertebrate (without bones) and has a large head, a beak-like mouth, eight arms (tentacles), a brain and three hearts. The squid grabs food with its tentacles, tearing the organism to bits with its powerful mouthparts. All squid emit ink when threatened and some are bioluminescent. The squid jet-propels itself by sucking in and then shooting out water from its body.
Squid live in every saltwater region in the world. Some species live near the surface while others live as deep as 1,000 feet. The giant squid (over 60 feet long) lives in trenches so deep that only a rare few have ever been sighted.
The Squid As Prey
Squid contribute to the ecosystem by providing food for other creatures. Humans are probably the squid’s greatest natural enemy, but sharks, seals, whales, dolphins, seabirds, deep-sea fish, and other squid also eat these tubular, multi-armed cephalopods.
The Squid As Predator
Squid help maintain the ecosystem by eating enormous quantities of food. Their specific diet differs depending on the region they live in, but the majority of their diet is krill, fish, crustaceans (like shrimp) and other squid.
Squid have a relatively short lifespan, primarily from 12 months to 18 months long. This is probably why squid reproduction is so prolific. One female squid can lay thousands of eggs, emitting them in long streams into the ocean. Some aquatic creatures feed on these eggs, while others eat the juvenile squid.