麻豆淫院

(麻豆淫院Org.com) -- Research sometimes means looking for one thing and finding another. Such was the case when biology professor Alice Gibb and her research team at Northern Arizona University witnessed a small amphibious fish, the mangrove rivulus, jump with apparent skill and purpose out of a small net and back into the water.

This was no random flop, like you might see from a trout that鈥檚 just been landed. The rivulus seemed to know what it was doing.

They hadn鈥檛 expected to see that behavior, even from a fish known to spend time out of the water. So before long, what began as a study on the evolution of feeding behavior was shifted to a study of how fish behave when stranded on land. And considering what is implied by the truism 鈥渓ike a fish out of water,鈥� the results came as another surprise.

Some fully aquatic fishes, as the author鈥檚 video clips show, also can jump effectively on land even without specialized anatomical attributes. This has significant implications for evolutionary biology, Gibb said, because the finding implies that 鈥渢he invasion of the land by vertebrates may have occurred much more frequently than has been previously thought.鈥�

The study is summarized in a paper, 鈥淟ike a Fish out of Water: Terrestrial Jumping by Fully Aquatic Fishes,鈥� that appears online in the Journal of Experimental Zoology Part A: Ecological Genetics and 麻豆淫院iology.
 
Gibb said the study 鈥渟upports a big-picture theory in evolution,鈥� which is that the nervous system, in its control of bones and muscles, can allow a new behavior to appear without necessarily bringing about a physical change.

In the case of aquatic fish, Gibb said, 鈥淭his shows that you don鈥檛 have to have legs or rigid pectoral fins to move around on land. So if you go back and look at the fossil record to try to say which fish could move around on land, you鈥檇 have a hard time knowing for sure.鈥�

The original feeding study began with guppies, then moved to a relative, the mangrove rivulus. Once the rivulus exhibited the tail-flip jumping maneuver, Gibb shifted the focus of the research. Eventually, the guppy came back into the picture. Literally.

鈥淲hen you do a study like this, you have to ask what your control is,鈥� Gibb said. 鈥淚f a known amphibious fish is a good jumper, then what鈥檚 a bad jumper?鈥�

Enter the guppy, a fully aquatic fish.

鈥淭he guppy jumped almost as well as the amphibious fish did,鈥� Gibb said. 鈥淎nd no one has ever suggested that a guppy is an amphibious fish.鈥� As a result, 鈥渨e put everything we could get our hands on鈥� in front of a high-speed camera, Gibb said. Some of those additional subjects included the mosquitofish, which has been introduced into tributaries of Oak Creek, and a common pet store zebra fish, which is a very distant relative of guppies and mosquitofish.

The mosquitofish 鈥渉as become our lab rat,鈥� Gibb said. 鈥淚t鈥檚 accessible, it comes from a group that has other jumpers, and it鈥檚 been reported that this fish jumps out of the water to get away from predators and then jumps back in.鈥�

That particular escape behavior, Gibb said, has never been filmed. Similar stories about other fish add to mostly anecdotal literature on the topic that 鈥渢ends to be old and very diffuse.鈥�

Today鈥檚 high-speed video systems give Gibb an opportunity to change that. What the cameras reveal is that both species produce 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.

Gibb and her team have discussed going into the field to capture video of fish performing this behavior in the wild. But for now Gibb and her colleagues are endeavoring to determine if there is directionality to voluntary locomotion on land and to investigate the genetic basis of the jumping behavior.

鈥淢aybe fishes that are very good at jumping are poor swimmers,鈥� Gibb said. 鈥淲e want to look at the compromises that may have been made to favor one behavior over another.鈥�