Why do we use fish in research?

Zebrafish are now the second most popular laboratory animal model. This is mostly due to them sharing over 70% of protein-coding genes with humans, but they also lay hundreds of clear eggs externally, which increases the possible sample size for experiments.

Scientists can watch the embryos develop over 24 hours, at which point the larvae hatch. Within three to four months, the zebrafish will be ready to breed. The adult zebrafish are fed a pelleted diet twice a day, with an extra feed of small live food like brine shrimp for enrichment. The young zebrafish, called fry until they are 70 days old, are fed four times each day with a mixture of powder, pelleted, and live food.

We have three main recirculating systems at the Crick, with three-litre tanks which each hold five adult fish per litre. Our facility also includes a quarantine room for imports from other facilities, a frog (Xenopus laevis) colony, and we are preparing to house guppies (Poeciliopsis spp.).
 
We provide various services to researchers at the Crick, including breeding, embryo collection, and superovulation of frogs. Breeding entails either setting up a male-female pair in a one-litre tank with a divider between the two or a mass spawn. Zebrafish tend to spawn at sunrise, so our team needs to be prompt in removing the divider to allow mating to take place. 

The Crick research we support with our zebrafish colony includes

• research towards understanding the causes of genetic eye disease
   
• understanding how cells communicate with each other and their environment as organisms develop
   
• understanding how the nervous system of the gut develops and functions
   
• understanding how simpler structures are moulded into complex organs in a developing embryo

Guppies will be used for understanding how new organs are created by studying the exceptional organ: the placenta.