Animal of the week: Zebrafish (Danio rerio)

"-The zebrafish a model organism on the rise"

This is one of the most common introductions in scientific articles relating to zebrafish research for the last 20 years. But what is a zebrafish?

The zebrafish is a small, 2-4 cm, cyprinid fish from the genus Danio. It has its origin in the southeastern himalaya region in asia with its main distribution in India. It has five blue horizontal stripes running laterally on its body hence the name zebrafish.

Zebrafish are omnivorous and forms small shoals of 6-10 individuals. They do not take care of their offspring and they spawn in the middle of the water column during the early morning. The eggs fall down to the bottom and lay in the substrate for a few days until they hatch. The first few days after hatching the young zebrafish are attached to stones and other things on the bottom substrate using a few specialized cells on the head. The stick to the bottom until they have consumed the yolk sac. When its consumed they let go of the substrate and make their way to the surface to engulf a small amount of air to fill their swim bladder. When thats done they swim around up in the water column feeding on various small crustaceans and other small creatures until they are large enough to spawn, after apporx. 3 months. 

The short generation time of about 3-4 months is one of the reasons for its popularity in scientific research. This mean that it is quick and rather easy to create different strains and mutants for research. Another reason is that the zebrafish have had its genome sequenced, so molecular studies on zebrafish is easy.