(p. 22) Earlier this week, and more than 2,700 feet underwater by the northern Great Barrier Reef, a remotely operated vehicle named SuBastian engaged in a stare-off with a burrito. That’s what the creature looked like from a distance: an untoasted cylinder floating eerily upright in the ocean’s twilight zone, like takeout from Triton.
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When Dr. Vecchione got a good look at the image, he knew exactly what it was: Spirula spirula, or the ram’s horn squid. Spirula is the only living squid to have an internal coiled shell, which it tucks under the fleshy flaps of its rear end, according to Jay C. Hunt, a biologist at East Stroudsburg University. The squid can also emit lime-green light from a large photophore, also located on its behind.
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Although the Spirula sighting may be a scientific first, it did not make a strong initial impression on the researchers onboard. “We’ve seen bobtail squids and dumbo octopuses where we say, ‘Wow, this is the cutest thing,’” Ms. Cornet said. “This one was weird-looking, and looking at us with its weird eye.”
Perhaps even more surprising than the creature’s cameo was its strange positioning. Scientists had always assumed that Spirula swam with its head pointed down and its gas-filled bottom in the air. When Dr. Vecchione caught living Spirulas in trawl nets and plopped them in cold water onboard, the “sort of alive” squids always floated rump-up, he said.
This hypothesis made sense; the squid’s gas-chambered shell buoyed it like a nautilus, after all. But it raised another question. Deeper-living creatures often point their photophores downward, disguising their silhouettes from predators lurking below. Beaming a green light toward the sky, on the other hand, serves no clear purpose. “This is neither common nor does it make sense,” Dr. Vecchione said.
But the Spirula caught on camera was clearly head-up, suggesting that its downward-gazing photophore was most likely used for counterillumination after all. “This makes sense,” Dr. Vecchione said.
Although the photophore mystery may now be solved, a right-side-up Spirula would seem to have a balancing problem, with the squid’s body mass precariously balanced on its buoyant shell. “When you design an R.O.V. you don’t put the heavy stuff on top and the floats on the bottom,” Dr. Lindsay said.
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(Note: the online version of the story was updated Oct. 31, 2020, and has the title “‘They’re Calling You on the Squid Phone’.” In the last sentence of the first paragraph quoted above, the phrase “like takeout from Triton” appears in the online, but not the print, version.)