Spring Break
URI professor discovers fish that can feed without vision
Betsy Cohen
Issue date: 4/29/09 Section: News
04/29/09 - A University of Rhode Island professor has made a new discovery in the world of marine sciences - a fish that can feed without using its vision.
According to Jacqueline Webb, biological sciences professor and coordinator of the URI Marine Biology Program, most fishes detect their prey visually.
She determined that a species of cichlids found in Lake Malawi of East Africa has a widened lateral line, improving their feeding abilities.
According to Webb, the mechanic-sensory lateral line system is a series of sensory organs called neuromasts that is composed of hair cells that respond to water flow and vibrations, but not sound.
The widened lateral line canal changes the physics of the water flow, which is taking place in the canal. Webb said she believes that it is an adaptation allowing cichlids to feed without using their sense of sight.
"We demonstrated that they can attack prey using their lateral line system and more importantly, they do that at night," Webb said. "In literature on these fishes, there are no records of cichlids feeding at night."
According to Webb, this is the first documentation of nocturnal and non-visual feeding in cichlids.
Daniel Bassett, a marine biologist from New Zealand, determined this cichlid species feeds at night and without the use of its vision through a preliminary experiment. Six Petri dishes were placed in a tank with sand on the bottom, an environment similar to the cichlid's natural habitat. In each of the Petri dishes, either a dead or living adult brine shrimp was tethered down. The cichlids were then released into the tank and their prey preferences were recorded during conditions of daylight, nighttime, intact and lacking of lateral-line capabilities. To deactivate their lateral lines, some cichlids were placed in a separate tank where a chemical solution of cobalt-chloride was administered.
"We asked the fishes to detect their prey," Webb said.
Cichlids feed by swimming over their food with their chin and detecting movements and vibrations in the water. When they sense a disturbance - in this case the flapping tails of the tethered live brine shrimp - they back up and attack their prey. Webb said the results of this experiment matched her original hypothesis.
According to Jacqueline Webb, biological sciences professor and coordinator of the URI Marine Biology Program, most fishes detect their prey visually.
She determined that a species of cichlids found in Lake Malawi of East Africa has a widened lateral line, improving their feeding abilities.
According to Webb, the mechanic-sensory lateral line system is a series of sensory organs called neuromasts that is composed of hair cells that respond to water flow and vibrations, but not sound.
The widened lateral line canal changes the physics of the water flow, which is taking place in the canal. Webb said she believes that it is an adaptation allowing cichlids to feed without using their sense of sight.
"We demonstrated that they can attack prey using their lateral line system and more importantly, they do that at night," Webb said. "In literature on these fishes, there are no records of cichlids feeding at night."
According to Webb, this is the first documentation of nocturnal and non-visual feeding in cichlids.
Daniel Bassett, a marine biologist from New Zealand, determined this cichlid species feeds at night and without the use of its vision through a preliminary experiment. Six Petri dishes were placed in a tank with sand on the bottom, an environment similar to the cichlid's natural habitat. In each of the Petri dishes, either a dead or living adult brine shrimp was tethered down. The cichlids were then released into the tank and their prey preferences were recorded during conditions of daylight, nighttime, intact and lacking of lateral-line capabilities. To deactivate their lateral lines, some cichlids were placed in a separate tank where a chemical solution of cobalt-chloride was administered.
"We asked the fishes to detect their prey," Webb said.
Cichlids feed by swimming over their food with their chin and detecting movements and vibrations in the water. When they sense a disturbance - in this case the flapping tails of the tethered live brine shrimp - they back up and attack their prey. Webb said the results of this experiment matched her original hypothesis.
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