Squids, which are carnivorous cephalopod mollusks of the order Teuthoidea, usually live for only two to three years. Squids are highly developed marine invertebrates with eyes that resemble human eyes.
Humans typically eat squids or use them as fish bait. The colossal squid, which is the largest invertebrate on the planet, can grow to 46 feet in length, according to The Columbia Encyclopedia. The giant squid can grow to 43 feet in length. The smallest type of squid is only about 2 inches long. Squids are known to release an ink-like substance when they sense that they are in danger. Some squids that live in deep waters have luminescent organs.