The bizarre fish that evolved for oceans, but lives on land

A new study has found that one of the world's strangest animals—a unique fish that lives on land and can leap large distances despite having no legs—has a rich and complex social life.

The odd lifestyle of the Pacific leaping blenny (Alticus arnoldorum) has been detailed for the first time in research findings that throw new light on how animal life first evolved to colonise the land.

Lead researcher Dr Terry Ord, of the UNSW Evolution and Ecology Research Centre and his colleagues also discovered that males are territorial and use complex visual displays to warn off rivals and attract mates.

Females were seen aggressively defending feeding territory at the start of their breeding season, while males displayed a red-coloured fin and nodded their heads vigorously to attract females to their closely defended rock holes.

The Pacific leaping blenny is a marine fish yet is terrestrial in all aspects of its daily adult life, eking out a precarious existence in the intertidal zone of rocky shores in Micronesia.

“This remarkable little fish seems to have made a highly successful transition across the water—land interface, although it is still needs to stay moist to enable it to breathe through its gills and skin,” said Ord, who is an evolutionary ecologist with a special interest in animal behaviour.

“Our study showed that life on land for a marine fish is heavily dependent on tide and temperature fluctuations, so much so that almost all activity is restricted to a brief period at mid-tide, the timing of which changes daily. During our field study on Guam we never saw one voluntary 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.

“I can tell you they are very hard to catch and are extremely agile on land. They move quickly over complex rocky surfaces using a unique tail-twisting behaviour combined with expanded pectoral and tail fins that let them cling to almost any firm surface. To reach higher ground in a hurry, they can also twist their bodies and flick their tails to leap many times their own body length,” Ord added.

The study has been published in the journal Ethology.