A team of biologists has demonstrated that cichlids, a group of African fish, can eat using the help of a non-visual sensory system, which is the first of its kind reported in this species.
Jacqueline Webb, a University of Rhode Island (URI) professor of biology, and her colleagues have demonstrated that a group of African cichlids feeds by using its lateral line sensory system to detect minute vibrations made by prey hidden in the sediments.
The lateral line system is composed of a canal embedded in the scales along the side of the body of a fish, around its eyes and on its lower jaw, which contain small groups of sensory hair cells that respond to water flow.
The lateral line system aids some fish in swimming upstream, navigation around obstacles, and the detection of predators and prey.
According to Webb, cichlids in the genus Aulonocara, which only live in Lake Malawi, have widened lateral line canals that are highly sensitive to vibrations and water flows.
They feed by gliding through the water with their chin close to the sand like a metal detector, seeking out twitching arthropods and other unseen prey items.
There are about 16 species of Aulonocara cichlids in Lake Malawi, all of which feed in the sand.
"These cichlids join a short list of fish that have been demonstrated to use their lateral line system to feed," said Webb.
"Since most of the fish with widened lateral line canals are found in the deep sea, it's difficult to study them. These cichlids can now be used as a model system for studying widened canals, and we can apply what we learn from them to the fish in the deep sea," she added.
Webb analyzed video of the swimming behavior of the fish in response to live and dead brine shrimp located on the surface of the sandy substrate in a tank.
She compared the fishes' ability to detect prey under light and dark conditions, and looked at their ability to detect prey when the lateral line system was chemically "deactivated."
She found that the fish were able to find live prey easily, even in darkness, but not without a healthy lateral line system.
Her discovery opens the door to the study of the convergent evolution of wide canals and raises the question of whether fish that feed non-visually have an ecological advantage over visual-only feeders.