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Grade level: 6-13+
Length: 4.5 minutes
Next Generation Science Standards: LS2.A, LS4.C
The Hawaiian bobtail squid (Euprymna scolopes) spends its days buried in sand and its nights stalking prey in the shallow waters off the coast of Hawaii. Just because the squid hunts at night, however, doesn’t mean that it relies on the cover of darkness. Its strategy is quite the opposite, in fact. This tiny speckled squid (an adult is about the size of your thumb) can cruise above its prey without casting a shadow—even on a moonlight night—thanks to its relationship with a bacterial partner, Vibrio fischeri. Juvenile bobtail squid are born without the bacteria; they recruit V. fischeri from the surrounding ocean water and then house the hitchhikers in a specialized light organ. In exchange for room and board, the bacteria help the squid hide at night—by glowing. The light they emit blots out the squid’s shadow, letting it sneak up on prey, and hide from predators.
Video Discussion Questions
- How does the Hawaiian bobtail squid hide its shadow?
- What is the advantage to the Hawaiian bobtail squid of being able to hide its shadow?
- How does the Hawaiian bobtail squid obtain the bacteria that help it hide its shadow?
- What kind of relationship do the Hawaiian bobtail squid and the bacteria it houses have? Do they exhibit mutualism, amensalism, commensalism, or something else?
- Can you think of another example in the animal kingdom of a similar kind of interspecies relationship?