It seems that the ocean truly is full of party animals. If you venture into the big blue, you can find disco clams, glittering schools of sardines, neon sharks and glowing jellyfish. Now, to add to the list, it turns out that there’s a squid which flickers like a strobe light. And thanks to National Geographic’s Crittercam, scientists are starting to understand why these flashy animals display this newly described behavior. According to a new study, the animals likely put on this light show to blend in with their environment. The intriguing findings can be found in The Journal of Experimental Biology.
The Humboldt squid (Dosidicus gigas), or “red devil” as it has been nicknamed, is a large carnivorous squid found in the Eastern Pacific Ocean, ranging from British Columbia to southern Chile. These predators can grow to be the size of a man, swimming up to 15 miles per hour (24 kph) in shoals of up to 1,200 individuals. Although these animals tend to live at depths of 200-700 meters (600-2300 ft), they have earned themselves a bit of a reputation with humans.
Their suckers are lined with teeth and their sharp beaks are more than capable of shredding flesh or chopping fish spines, and attacks on humans and recording equipment have been documented. While some see them as an aggressive species, they’ve only gone for humans when provoked by shiny or flashing diving gear and tend to be curious rather than pugnacious.
Like all coleoid cephalopods (squid, cuttlefish and octopus), the Humbolt squid is able to change its skin color through the use of specialized skin cells called chromatophores. These tiny organs contain a sac of pigment that can be expanded, making it visible to the observer. But unlike some species of squid, which can display several different colors, D. gigas can only switch between red and white since it only possesses reddish-brown chromatophores. While this much was known, no one had ever studied this so-called chromogenic behavior before, until now.
For the investigation, scientists from Stanford University and the National Geographic Society mounted cameras on three 1.5-to-1.8-meter-long (5-6 ft) squid, which had never been done before on any species of squid. They then analyzed the recorded footage, some of which can be found on Nao Geo's website, to see if they could work out what purpose the flashing behavior could be serving.
They found that these animals actually display three different chromogenic behaviors: static patterns, rapid and rhythmic “flashing” of the whole body, and a more subtle “flickering” which consisted of waves of red and white that travel across the body. The bold flashing between white and red was almost always observed when other squid were around, which is why the researchers think it is probably a form of communication. What they are trying to convey, however, remains unknown, although they may be advertising themselves to prospective mates.
The flickering, on the other hand, could be acting as a form of camouflage, as the patterns appear to mimic the reflections of sunlight in the water. Since these animals are unable to use an array of colors to disguise themselves as objects such as rocks, like other species, this flickering may help them blend in and confuse predators.
[Via JEB, National Geographic and Encyclopedia of Life]
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