In a clutch of eggs, some zebrafish are the runts of the litter and may appear younger because of their diminutive size. This is the case for the two zebrafish above. The two are in fact 5-day old siblings. At this stage of development, the zebrafish larvae have hatched from their transparent eggs and have begun feeding on tiny single celled organisms called paramecium. As the zebrafish larvae grow, they start to feed on brine shrimp and by three months of age, the zebrafish will be fully grown adults.

Contributed by Michka Sharpe, a fifth year graduate student in the Biological and Biomedical Sciences program at Harvard Medical School, and our Featured Artist for August 2017.