“Legs” allow fish to track prey without seeing it – 06/10/2024 – Science

The fish known as the false brown flycatcher (Prionotos carolinus) performed two apparent evolutionary miracles: Not only did he evolve “legs” that help him turn over the sea floor, he also equipped these appendages with chemical detectors, similar to those that detect flavors on the human tongue.

These two sensory tricks help the animal, which can be found on the Atlantic coast of the United States, find prey under the sand even without seeing it. This is what reveals A He studies Published on October 26 in the specialized magazine Current biology. This work is another example of how apparently radical changes in an animal’s evolutionary path can end up appearing trivial, with “workarounds” involving already existing capabilities.

“We’re talking about a fish whose ‘legs’ grew using the same genes that contribute to the growth of our limbs. It then regenerated those legs to find prey, using the same genes that our tongues use to taste food. This is very much the case,” said Nicholas Belluno, of the Department of Molecular and Cellular Biology. “It’s really crazy,” he joked in an official statement at Harvard University.

Belluno is one of the coordinators of the study conducted on this species and its relatives, along with David Kingsley, of Stanford University. The two became interested in the creature during a visit to the Woods Hole Marine Biological Laboratory, on the East Coast of the United States, when they learned that other fish were watching it because of its ability to find prey hidden under the sea. Substrate.

They then decided to take some samples of the brown false flytrap, which can grow up to 40 cm long, to the laboratory. They devised a series of experiments whose goal was to discover how accurately animals were able to find their meals.

The first step was to place the animals in tanks in which both the shellfish and capsules of raw or diluted extract of the flesh of these shellfish were buried in the sand at the bottom, as well as capsules in which there was only seawater. .

In this laboratory scenario, the fish took turns swimming and treading sand using their “feet” (actually six modified pectoral fin structures). They were always able to find buried oysters and capsules containing mollusc extract, but the strange thing was that they were not interested in capsules containing seawater. This suggests that there is something beyond the shape of things behind animals’ ability to find food.

This prompted scientists to conduct a direct analysis of the interaction of the “legs” with the nervous system of fish, and to measure the electrical activity of the spinal nerves connected to the legs. The result: everything indicates that the paws were mechanically sensitive (that is, they reacted to touch and pressure, like human skin), but they also reacted to various amino acids, naturally found in foods of protein origin (such as seafood, of course). .

The team also conducted a series of more detailed anatomical and genomic analyses, including a comparative one p. Carolinus With another species of its kind, which is p. evolans. The interesting thing here is that although it also has “legs”,… p. evolans Do not use them for drilling.

Furthermore, the “little legs” of this second species are stick-shaped, while those of the second species p. carolinos, Shovel shape. Finally, the first type is covered with structures that closely resemble, in structure, taste buds distributed across a person’s tongue.

And that’s exactly what they are – one of the most activated stretches of DNA in the cells of these papillae is the one that contains the recipe for producing taste receptors. In other words, the cell structure whose role is to receive molecules associated with taste.

“Although many of these features appear new, they are typically built from genes and molecular modules that have been around a long time,” Kingsley says. “That’s how evolution works: modifying old parts to build new things.”