A species of fish known for its unusual ability to climbs trees has now been spotted hopping across water. The team that made the find says that it seems to be an entirely new form of fish locomotion.
“We already considered this fish to be very special since it was so adept at climbing trees and rock faces,” says Parvez Alam at the University of Edinburgh, UK. “But the hopping was even more bizarre a finding than we had expected.”
Mudskippers are amphibious fish that can breathe in and out of water and use their pectoral fins to move about on land. They are considered by some to be living examples of how organisms may have transitioned from water to land 350 to 400 million years ago.
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Alam and his colleagues originally went to the Indonesian island of Java to study how the dusky-gilled mudskipper (Periophthalmus variabilis) climbs inclined surfaces such as trees, rocks and mangrove roots.
But when the researchers approached the mudskippers, they saw the fish leap from trees or rocks onto the neighbouring water and perform successive hops across the surface, occasionally even ending up back on land.
An analysis of video footage revealed that short, rapid bursts of tail-beating make the hopping possible. This enables the fish to accelerate on the water’s surface and propel itself into the air. The fish briefly remains airborne before landing back onto the water to repeat the process again for a subsequent hop.
Flying fish are known to glide over water in a similar fashion but the mudskipper’s hopping motion differs because it doesn’t submerge after each hop or use its fins to enter a glide.
“I think the movement is different enough in how it works to be considered separately,” says Alice Gibb, who studies fish locomotion at Northern Arizona University. “This observation highlights how well adapted mudskippers are to life on land, where returning to the water appears to be actively avoided, even when danger is imminent.”
Zoology
