Natures wonders: walking fish (Introduction)

by David Turell , Thursday, September 26, 2024, 23:07 (25 days ago) @ David Turell

Only in water:

https://www.sciencenews.org/article/fish-legs-taste-prey-sea-robin

"Some sea robins, a group of fishes with two winglike fins and six crablike legs, use their legs to dig in sand and find buried prey with a sense much like taste, researchers report in two papers published September 26 in Current Biology. Most sea robins seem to use their legs only for walking. But an ancient gene important for the formation of limbs in humans and other animals, as well as a gene involved in building taste buds, helped a few species develop legs that taste.

“'New things came from old parts,” says David Kingsley, a developmental biologist at Stanford University. A walking fish with taste organs on its limbs may look “really new and cool and different, but when you dig in… the new things have come by taking a tool kit of preexisting genes and deploying them in new ways.”

"Northern sea robins (Prionotus carolinus) are skilled at finding buried crabs or shrimp to snag a meal. So skilled, in fact, that other fish seem to follow along to take advantage of any spoils. Previous studies suggested that northern sea robin legs could pick up chemical cues, but it was unclear if the limbs could sense anything as they dug into the seafloor.

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"Most sea robins, including a non-digging species called the striped sea robin (P. evolans), have smooth, rod-shaped legs that probably can’t taste, the team discovered. That difference suggests that northern sea robins and another digging relative, the leopard sea robin (P. scitulus), are among a few species benefitting from an “evolutionary innovation,” says Amy Herbert, a developmental biologist at Stanford University.

"Though the legs aren’t technically legs, Herbert notes. While the fishes do use the appendages for moving around — which prompted the team to call them legs — their position on a sea robin’s body is more akin to using arms to walk.

"Whether arms or legs, Jiang wonders whether the limbs’ papillae can sense bitter compounds that don’t signal food but instead tell sea robins when they’ve found something that they want to avoid. He also wants to know if the taste buds in sea robin mouths detect the same tastes that their legs do. “Once they actually find food, what’s the next step?'”

Comment: not a step toward land. But a fascinating twist of evolution. Take a look at the video as the fish scavenges.