Richard Robinson / Gloomy octopus (Octopus tetricus), Captive. September.

Solvin Zankl / Big fin squid (Magnapinna atlantica) species only known from two specimens collected in the northern Atlantic Ocean. First described in 2006. It is characterised by several unique morphological featu...

Solvin Zankl / Big fin squid (Magnapinna atlantica) species known only from two specimens collected in the northern Atlantic Ocean. First described in 2006. It is characterised by several unique morphological featu...

Norbert Wu / Humboldt Squid (Dosidicus gigas) close-up of suckers lined with razor-sharp teeth, Sea of Cortez, Baja California, Mexico

Andy Reisinger / Octopus tentacles showing suckers, New Zealand

Franco Banfi / Mimic octopus (Thaumoctopus mimicus) swimming midwater, Bethelem III, Minahasa Lagoon, Manado, Sulawesi, Indonesia, Pacific Ocean.

Franco Banfi / Mimic octopus (Thaumoctopus mimicus) swimming down to seabed, Bethelem III, Minahasa Lagoon, Manado, Sulawesi, Indonesia, Pacific Ocean.

David Shale / Glowing sucker octopus (Stauroteuthis syrtensis) at a depth of 830m, Gulf of Maine, Atlantic Ocean.

Joel Sartore / Photo Ark / Giant Pacific octopus (Enteroctopus dofleini) female, portrait, Alaska SeaLife Center. Captive.

Tony Wu / Mature lumpfish (Eumicrotremus taranetzi) with visible disk comprising modified pelvic fins used as sucker to adhere to rocks and other surfaces. Pacific Ocean, Hokkaido, Japan.

Fred Bavendam / Pacific giant octopus (Enteroctopus dofleini) moving away releasing a cloud of ink, British Columbia, Canada, Pacific Ocean. Some backscatter digitally removed.

Fred Bavendam / Pacific giant octopus (Enteroctopus dofleini) sheltering in den with the remains of Abalone shells left at entrance after feeding, British Columbia, Canada, Pacific Ocean.