Blood vessels in the head of a zebrafish embryo

Confocal micrograph of arteries (nuclei; red) and veins (blue) in the trunk of a 3 day old zebrafish embryo. Ventral view with the embryo facing left and the aorta and cardinal vein on the horizontal plane. Zebrafish are a powerful tool for studying development of a fully functioning vascular system, as this forms in a similar way in other animals including mammals. This zebrafish has been genetically engineered so that the arteries and veins express different fluorescent proteins. As zebrafish embryos are transparent, these arteries and veins can then be visualised as the circulatory system develops. Horizontal width of image is 212.55 micrometres.