Animals earn their stripes

While fish are not the most intelligent animals, geneticists can still learn about the mysteries of life from the humble zebrafish.

Studies with zebrafish are being conducted at the ARC Special Research Centre for the Molecular Genetics of Development at Adelaide University. Researchers are searching for genes expressed when the brain's first cells are generated, and the future brain divides into various subregions.

The zebrafish (Danio rerio) is a small freshwater fish about 3 cm long, named for its prominent black and white stripes. Originating in India, the fish are now distributed across the world.

Zebrafish have been studied by developmental researchers for more than 30 years. They are small and tolerate high densities, so they are inexpensive to keep and breed in large numbers. A single female can produce more than 200 eggs in a week, and once fertilised, the embryos develop externally and are transparent. Development is quick, with fertilisation to hatching taking only three days. What a zebrafish embryo does in three days, takes a human three months.

Zebrafish are studied by mutating the embryo's own genes and observing what effect this has on development. Such studies reveal how nerve cells develop in the brain and nervous system, and which genes control the development of the backbone.

The understanding of the genetics of zebrafish may result in the entire zebrafish genome being sequenced by the end of 2001. While a great deal will be known about the development of zebrafish, the real benefits will lie in the wider implications of knowing how the brain develops. It will help the understanding of diseases such as Parkinson's, spina bifida, Alzheimers and other human afflictions that have an inherited component or are the result of incomplete embryonic development.