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 work is answering fundamental questions about deep-sea cephalopods and providing vital information that resource managers can use to inform their decision-making about the ocean.

The deep sea is closer than you think. What we do on land affects the ocean, even the animals and environments deep below the surface. By choosing sustainable seafood, refusing single-use plastic, and reducing our carbon footprint, we can help protect the amazing animals of the deep.


Learn more about the octopus squid and other fascinating animals of the deep at our Animals of the Deep gallery: https://www.mbari.org/animal/octopus-...

Script writer: Megan Bassett
Science advisor: Stephanie Bush
Editor: Ted Blanco
Narrator: Susan von Thun
Production team: Heidi Cullen, Madeline Go, Larissa Lemon, Raúl Nava, Kyra Schlining, Nancy Jacobsen Stout, Susan von Thun
Music: Brave Horizon No Drums by Humans Win


References:
Bush, S.L., and B.H. Robison. 2007. Ink utilization by mesopelagic squid. Marine Biology, 152: 485–-494. dx.doi.org/10.1007/s00227-007-0684-2

Bush, S.L., B.H. Robison, and R.L. Caldwell. 2009. Behaving in the dark: Locomotor, chromatic, postural, and bioluminescent behaviors of the deep-sea squid Octopoteuthis deletron Young 1972. Biological Bulletin, 216: 7–-22. http://dx.doi.org/10.1086/BBLv216n1p7

Hoving, H.J.T., S.L. Bush, and B.H. Robison. 2011. A shot in the dark: same-sex sexual behaviour in a deep-sea squid. Biology Letters, 8(2): 287–-290. doi.org/10.1098/rsbl.2011.0680