Fish can detect numbers of objects, even when they can’t see, according to a report from The Scientist.
Christian Agrillo of the University of Padova, Italy, showed that, despite its lack of vision, a blind Somali cavefish could distinguish between a school of fish and one that was double in size. Agrillo discovered that the cavefish used sensory information from its lateral line to determine quantity difference.
It turns out that being able to sense which group is bigger is a widespread evolutionary trait. Joining a bigger group offers an organism protection from predators and an advantage in finding mates. Fish and other animals have been shown to detect quantities using not only visual but also others types of sensory input. Ants, spiders and bees have recently been shown to “count” as well.
Top image: A blind cavefish. (Credit: Matthew Niemiller)