There is still much we don't know about the Humboldt squid. Image Credit: NOAA / MBARI 2006
The Humboldt squid has evolved a novel solution to the problem of communicating in the depths of the ocean.
Found up to 2,300ft beneath the surface of the eastern Pacific Ocean, the Humboldt squid can grow up to 1.5 meters in length and typically travels in large groups of up to 1,200 individuals.
One of their most fascinating traits is their ability to produce dazzling bioluminescent displays using special pigment cells called chromatophores.
Such displays serve as a means of communication between individuals, however it has long remained unclear exactly how the squid are able to see each other in the darkness at such depths.
Now a new study by Ben Burford of Stanford University and Bruce Robison of the Monterey Bay Aquarium Research Institute has shed new light on the mystery by showing that the squid have special bioluminescent light organs called photophores that effectively serve as a backlight.
"Humboldt squids have small aggregations of luminescent tissue - little dots sprinkled throughout their muscles," said Burford. "Instead of projecting light outwards, what these photophores do is radiate light within the body tissue. They make the whole animal glow."
By using a remote-operated vehicle to study the squid in their natural habitat, the researchers found that the cephalopods used their own bioluminescent 'language', is it were, to communicate.
One example of this - a distinctive 'flickering' - could be seen while the squid hunted down prey.
"It's like turn signaling in traffic," said Burford. "Driving is dangerous, being a Humboldt squid in a group is dangerous and you've got to signal to tell people what you're going to do and that they shouldn't mess with you while you're doing it."