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Zebrafish eggs

Zebra fish embryos reside in transparent eggs and the eggs hatch after only two days.

Something fishy in biology

By Carol Ford

From eNews, August 18, 2005

Paul Myers joined the Biology Discipline at the University of Minnesota, Morris, back in 2000 and brought with him a wealth of experience in zebra fish research. However, it wasn't his initial intent as a bio undergrad to one day find himself in a lab full of aquariums.

"Originally, I was interested in the functions of the human brain," he recalls. "But first, I needed a simple model to work with. Fish are simple, especially young fish, so that led me to the area of early brain development." Myers found zebra fish to be well suited to his research because of their rapid development. Eggs are laid one morning and they hatch after only two days.

Today, zebra fish are a hot scientific model, says Myers. Researchers are exploring everything from mutations to genomes with these little fish. "When I started working with zebra fish, there were six of us studying them. Now there are thousands," he says.

Myers's research is currently focused in two areas: the cellular effects of ethanol on zebra fish embryos and the genetics of fish behavior. The former has direct implications for those who want a clear understanding of the effects of fetal alcohol syndrome on human embryos.

"Obviously, this research can't be done on human embryos, but we can study the effects of different alcohol solutions on young fish," says Myers. "Unlike mammal embryos, zebra fish embryos reside in transparent eggs and are transparent themselves. Zebra fish are also cheap, and they lay lots of eggs."

He has enlisted the help of student research assistants to gather and analyze data on this project. Two years ago, Matt Larson (now in med school) took his ethanol effects research to the National Developmental Biological Society Conference and was awarded the Best Undergraduate Presentation award. This year, senior Amanda Woodle (who has been accepted to the University of Minnesota, Duluth, medical school) is continuing the ethanol study.

"...this research can't be done on human embryos, but we can study the effects of different alcohol solutions on young fish," says Myers.

In addition to their transparent bodies, zebra fish also have well-established, distinct genetic lines that can be studied. This is a great advantage in Myers's second area of research--the genetics of unnatural behaviors in fish, which has a real impact in the commercial world of stocking game fish in the wild.

One of the problems with raising captive game fish for release is that the successful ones have learned to adapt to conditions, which don't mimic natural circumstances. For example, game fish raised for release are fed on the surface of the water. These surface feeders get the most food, are larger and healthier; and, therefore, selected for breeding. But in the wild, surface feeders get picked off by predators more easily.

"These [captive or bred fish] don't give anglers much of a challenge," notes Myers. "Sports fishermen prefer smart fish. So this is a real issue on lakes that are being stocked."

Zebra fish offer a useful opportunity to study this wild and captive behavioral problem because of their own domestication as tank fish. The British first collected zebra fish in the 1830s. Over time, researchers began to notice that lab-bred fish were not as smart as their wild counterparts. In recent years, researchers were able to collect small numbers of wild specimens from Nepal, Thailand, and locations on the Upper Ganges River. These smarter, wild fish and their descendents are timid, afraid of people, and have different feeding behaviors compared to lab fish.

Myers was able to obtain some fish from this wild genetic line to compare their behaviors with his own lab fish. His research student, Mike Peterson, is working on quantifying their differing behavioral responses to light and dark, feeding, and the movement of large objects.

"Once behavioral differences have been quantified, we can cross breeding lines to find out what comes out," says Myers. "And if we can isolate strains of fish with certain behaviors, molecular biologists can in turn examine [those behaviors] to find out what's going on." That research can then be applied to game fish.