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When biologist Alice Gibb and her research team witnessed a small amphibious fish, the mangrove rivulus, jump out of a net and back into the water they inadvertently discovered the evolutionary traits which allow fish to temporarily invade the land. Their resulting study, published in JEZ A: Ecological Genetics and Physiology, reveals how fully aquatic fish can jump effectively on land without specialized anatomical attributes.

“These findings have significant implications for evolutionary biology,” Gibb said, “because it suggests the invasion of the land by vertebrates may have occurred much more frequently than has been previously thought.”.

In the case of aquatic fish this ability shows that species without legs or rigid pectoral fins can move around on land. This raises the possibillity that more species have been able to invade the land than the fossil record initially suggests.

The team originally intended to study the feeding behavior of a related species, the guppy and once the rivulus exhibited the tail-flip jumping maneuver the team turned their attention back to this fully aquatic fish.

“Interestingly the guppy jumped almost as well as the amphibious fish did,” said Gibb, “and no one has ever suggested that a guppy is an amphibious fish.”
The team set about recording several additional species in front of a high-speed camera, including the mosquitofish, which has been introduced into local tributaries of Oak Creek in Arizona, and a common pet store zebra fish, which is a very distant relative of guppies.

“The mosquitofish became our lab rat,” said Gibb. “It’s accessible, it comes from a group that has other jumpers, and it’s been reported that this fish jumps out of the water to get away from predators and then jumps back in.”

That particular escape behavior had never been filmed, yet using the high-speed video systems the team revealed that both species produced a coordinated maneuver in which the fish curls its head toward the tail and then pushes off the ground to propel itself through the air.

To further their research Gibb and her colleagues are endeavoring to determine if there is directionality to voluntary movement on land and to investigate the genetic basis of the jumping behavior.

“Maybe fishes that are very good at jumping are poor swimmers,” Gibb said. “We want to look at the compromises that may have been made to favor one behavior over another.”


This study is published in JEZ A: Ecological Genetics and Physiology. 
Full Citation: Gibb. A, Ashley-Ross. M, Pace. C, Long. J, “Fish out of Water: Terrestrial Jumping by

Fully Aquatic Fishes”, Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, Wiley-Blackwell, DOI: 10.1002/jez.711

Video Footage: http://jan.ucc.nau.edu/acg/video.html
Author: Dr Alice Gibb

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