The zebrafish oxytocin neurons arise from the hypothalamus and grow in towards the posterior pituitary. This is illustrated in the video using live-imaging of zebrafish embryos under a two-photon microscope, where-in the depth of the neuron projections are colour-coded.
Transgenic zebrafish, in which the blood vessels are fluroscently labelled, are imaged live under a two-photon microscope to observe the growth and development of the cerebral vasculature.
When zebrafish are kept isolated in a novel arena, they tend to spend most of the time in a region where they can see a shoal of fish across a transparent barrier, showing that they are social animals. Zebrafish show a strong tendency to be social from about one month of age.