London, October 18 : Squid squirt ink to alert their companions to the presence of predators, according to a study.
"When fish bleed, the scent of their blood has been proven to alert nearby fish of danger, so I wondered if ink was also being used as some form of alarm," New Scientist quoted James Wood, a marine biologist at the Bermuda Institute of Ocean Sciences, as saying.
For their study, Wood and his colleagues gathered ink from individual squid by scaring them with a shake of their aquaria.
The researchers either added a dose of ink to a squid's aquarium, to a nearby unoccupied aquarium, or added ink that had had the dark melanin colouring removed.
They said that the Caribbean reef squid took evasive action in the first two cases.
The team observed that ink that lacked melanin did not have any effect on squid behaviour, indicating that it was a visual, not a chemical, signal.
Unlike these reef squid that are social, and live where it is light, "the majority of squid are asocial and live in darkness, so it would be interesting to carry out similar work in other species," said Stephanie Bush, of Monterey Bay Aquarium Research Institute.
An article on the study has been published in the Journal of Experimental Marine Biology and Ecology.