The study, led by Dr. Terry Ord of the University of New South Wales Evolution and Ecology Research Centre and published in the journal Ethology, sheds light for the first time on the animal lifestyle of the land fish.
The Pacific leaping blenny (Alticus arnoldorum) is a marine fish but spends most of its time on the rocky shores all over Guam, often moving and leaping through rocky crevices.
“This remarkable little fish seems to have made a highly successful transition across the water to land interface, although it still needs to stay moist to enable it to breathe through its gills and skin,” said Dr. Ord.
Ord said the blenny has a brief window of opportunity to stay on land, depending on the tide and temperature fluctuations, most of which is during mid-tide when the water is high enough to keep the fish moist but waves aren’t strong enough to carry it out to sea.
“During our field study on Guam, we never saw one voluntarily return to water. Indeed, they spend much of their time actively avoiding submersion by incoming waves, even when we tried to capture them for study,” he said.
Hard to catch
“I can tell you they are very hard to catch and are extremely agile on land,” he added.
Combined with expanded pectoral and tail fins that allow them to cling to almost any firm surface, the leaping fish moves using a unique tail-twisting behavior, he noted. The fish can also leap far distances by twisting its body and flicking its tail.
Not only are the fish unique because of their ability to survive on land, “walk” and leap, the Pacific leaping blenny also has a surprisingly complex social life, according to the research.
Males are territorial and attract mates to their rock holes by displaying their fins and nodding their heads. The research team also filmed females inspecting breeding holes before entering them with a chosen mate.
While the female lays its eggs in rock holes, it’s the males who are left to guard the eggs, the study noted.
“The Pacific leaping blenny offers a unique opportunity to discover in a living animal how a water to land transition has taken place,” said Ord.
“We know that our ancient ancestors evolved originally from lobe-finned fish but, today, all such fish are fully aquatic. Within the blenny family, however, are species that are either highly terrestrial, amphibious or entirely aquatic. Remarkably, representatives of all these types can be found on or around Guam, making it a unique evolutionary laboratory.”
