to 1.4 inches (3.5 cm) in mantle length
other squid, octopuses, cuttlefishes, and the chambered nautilus; Phylum: Mollusca; Class: Cephalopoda; Family: Sepiolidae
Pacific Ocean; shallow coastal waters off Hawaii
Native to the Pacific Ocean, this species can be found in shallow coastal waters off Hawaii. It buries itself in sand or muddy areas near sea grass beds during the day—even gluing sand grains to its body to form camouflage—and emerges at night to feed.
This pear-shaped squid is akin to a wizard with its own invisibility cloak due to a symbiotic relationship with bioluminescent bacteria that lives in a special light organ in its mantle. When the squid leaves the safety of the seafloor to hunt at night, the bacteria hides the squid's silhouette by matching the amount of light hitting the top of its mantle—making it virtually invisible in moonlit waters when viewed from below. In return, the small squid provides the bacteria with a sugar and amino acid solution to feed on.
Hawaiian bobtail squid hatchlings aren't born with this bacteria; they secrete a mucus around their light organs to capture it. Less than a day after hatching, juvenile squid are able to "disappear" from predators just like their elders.
Hawaiian bobtail squid are cephalopods related to other squid, octopuses, cuttlefishes and the chambered nautilus. They have a relatively short life span, living only three to 10 months, but grow quickly. They're able to reproduce just two months after hatching, and breed only once. Females lay eggs on the undersides of coral ledges in shallows, and die shortly thereafter.
The population size of the Hawaiian bobtail squid is currently unknown as are threats to this species. Although human impact on the ocean is growing, so is the knowledge that we depend on healthy seas. Working together, people can discover solutions to pollution, overfishing and other threats to the oceans.
The Hawaiian monk seal is a common predator of the Hawaiian bobtail squid.
Each morning a squid vents 90 percent of its bioluminescent bacteria back into the sea water. The bacteria replenishes itself during the day when the squid is buried in the sand. By evening, when it's time to feed, the squid has a new crop of bacteria in its light organ that'll help it evade predators.
Materials science experts in the U.S. Air Force have studied the symbiotic relationship between the squid and its bacteria to see if the reflective qualities could be used to improve their aircraft camouflage.