View the images from our previous Award winners.

Zebrafish embryo

Annie Cavanagh and David McCarthy

Browse Wellcome Images for other images like this.

See and download this image from Wellcome Images.

Scanning electron micrograph of a four-day-old zebrafish embryo. To capture this image, the zebrafish was physically attached to a stub (specimen holder) by its tail and tilted to 65 degrees. As zebrafish embryos are approximately 1 cm in length, making the whole embryo too big to be captured in a single image, three separate images had to be taken along its length and then stitched together digitally. Colour was then added to the black-and-white image using tones and shading to try and represent the reflectiveness of fish scales. The zebrafish is a small, tropical, freshwater fish that originally comes from Asia. It is commonly used as a model organism to study developmental biology and neurodegeneration (the deterioration or death of nerve cells) in vertebrates.

How was this image created?

The image was captured by David using an FEI Quanta 200F scanning electron microscope. Prior to imaging, the embryo was chemically fixed, dehydrated in graduated alcohol, then dried and coated with gold particles 5 nanometres in size. The zebrafish was then physically attached to a stub (specimen holder) by its tail and tilted to 65 degrees to reveal the morphology seen here. As zebrafish embryos are approximately 1 cm in length, making them too big to be captured in a single image, three separate images had to be taken along the length of the embryo and then stitched together digitally. Annie then added colour to the black-and-white image "using tones and shading to try and represent the reflections from fish scales".

Why is the zebrafish used as a model organism?

Zebrafish embryos are transparent and develop outside the female's body, so you can watch their internal organs change as they grow. They develop very quickly and are usually ready to hatch 48 hours after fertilisation. Their genome has been sequenced, they can be genetically modified, and strains carrying characterised mutations are readily available. They also cost relatively little to feed and house.