SQUIDs

Squids are marine cephalopods in the order Teuthida. They include about 300 described species and occupy a wide range of habitats, from coastal zones to the deep open ocean, at depths from the surface to several thousand meters. Most squids are pelagic and migratory, while a few live near the sea floor.

Anatomy: A typical squid has a soft mantle, eight arms and two longer feeding tentacles, a beak, and a chitinous internal shell called a pen. They possess large brains and complex eyes. Blood is blue and copper-based (hemocyanin); three hearts pump blood through gills and the body.

Locomotion and camouflage: Squids swim by jet propulsion, expelling water through a siphon, with fins providing steering. They are capable of rapid color changes using chromatophores, iridophores, and leucophores for camouflage, communication, and signaling.

Diet and ecology: Squids are carnivores, feeding on fish, crustaceans, and other cephalopods. They use their tentacles to grasp prey and a sharp beak to kill it. Predators include larger fish, seals, and toothed whales. Many species produce ink as a defensive distraction.

Life cycle: Most squids have short lifespans and reproduce once, laying egg masses and dying after spawning. Species vary in maturity and reproductive timing, with some deep-sea species living longer.

Human interaction: Squids are hunted commercially for food and used in research. Overfishing and environmental changes can affect populations, and management seeks to balance harvest with ecosystem health.