The octopus squid breaks the rules, having 8 arms instead of 10

The octopus squid (Octopoteuthis deletron) is unusual among squids. Typically, squids have eight arms and two long tentacles, making a total of 10 appendages. But as young Octopoteuthis mature into adults, their two feeding tentacles are reabsorbed into their bodies. Eight arms are not the only thing that stands out about this species. While exploring the midwater, we often encounter octopus squid in a distinctive posture: large fins spread wide, and arms with twinkling tips curled above the head. Light-producing organs called photophores flash with bioluminescence at the end of each arm. MBARI has spent several decades studying Octopoteuthis. Cameras on our advanced underwater robots have revealed insights into the mysterious lives of octopus squid, from their unique behaviors to their defensive strategies. Octopus squid and their deep-dwelling kin play a vital role in ocean food webs. Despite their ecological importance, we still know very little about the lives of deep-sea squids. MBARI’s wor