Ecuadorian cavefish
Most creatures use their teeth for eating and protection, but a school of fish in the dark waters of a cave in Ecuador has developed a different purpose for its chomping whites: sensory navigation.
University researchers, along with the National Institutes of Health and Pontificia Universidad Catolica del Ecuador, discovered these fish use teeth nested on their skin — called denticles — to project hydrodynamic images that allow the fish to feel their way through the darkness and fast currents of the caves.
Researchers said the discovery of this evolutionary phenomenon, which has been found exclusively in the cave, suggests there are other creatures with similarly unusual characteristics still yet to be uncovered.
“This was an unexpected discovery,” NIH researcher Gal Haspel said. “But serendipity in science is about being prepared for something unexpected to happen.”
The discovery began when biology professor Daphne Soares flipped through a few local tourist guides about the cave while in Ecuador for research.
Out of habit, Soares collected a few samples during her visit to the cave. When she brought them to the lab for electron microscope scanning, she noticed the fish were covered with skin teeth but had few navigational water current detectors, called neuromasts.
Curiosity aroused, Soares, along with Haspel, an Ecuadorian undergraduate student and two undergraduate students from this university, embarked on an expedition to explore the cave and spent two weeks poring over the fish’s anatomy and morphology, studying their form and structure. The results of their research were published in August in the scientific journal Current Biology.
What the group found was shocking: the skin teeth had taken over the role of neuromasts by adapting to the dark depths and fast currents of the cave. Unlike most cavefish, which use neuromasts to move around, these creatures use denticles as navigational devices. As the teeth deflect the currents, the fish can detect the direction of water flow and determine the distance to the bottom of the cave, the study reports.
Researchers believe the neuromasts were filtered out by nature because they could not withstand the cave’s high currents.
“Think of trying to hear someone talking in a rock concert — the background noise is too high,” Soares said in a news release.
Other fish use these teeth for more traditional purposes, such as protection, cutting and reducing drag. The presence of the trait in other creatures remains fishy, the researchers said.
“Every cave can be thought of as an experiment in adaptation, and in each one, evolution might take a different course,” Haspel said.
