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The jumping fish with a tale of the earliest land creatures

By Colin Ricketts - 31 Aug 2011 15:47:0 GMT
The jumping fish with a tale of the earliest land creatures

A fish that lives on land and ignores the fact it has no legs to leap prodigious distances has even more mysteries to reveal according to new research.

The study, study published in the journal Ethology and led by Dr Terry Ord, of the UNSW Evolution and Ecology Research Centre is the first detailed examination of the extraordinary life of the Pacific leaping blenny.

Learning more about this fish out of water could provide important new evidence on how animal life first came out of the seas.

The blenny lives most of its adult life in the rocky intertidal zone of Micronesia, although like all fish it is dependent on water to breathe says Dr Ord.

"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," Dr Ord said.

"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."

The blennies hide away at high and low tide, emerging to feed in the mid-tide period and engage in complex socialising. The males use complicated visual displays to protect their territories from other blennies and snare the best mates with a head-nodding display of red fins.

Sadly, as the breeding and early life of the blennies takes place in their secret rocky lairs little is known about this stage of their lives yet, although it does seem that males take on most of the work after the females lay eggs and leap away.

"The Pacific leaping blenny offers a unique opportunity to discover in a living animal how a water-land transition has taken place," says Dr 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."

Related Video: Land-dwelling fish - Pacific leaping blenny as it goes about it's day on the rocky foreshores of Guam

Top Image Credit: A Pacific leaping blenny (Alticus arnoldorum) on the intertidal rocks at Taga'chang, Guam, 10 June 2011. © Georgina Cooke courtesy of Australian Museum