Barnacle (Balanus amphitrite) nauplius larvae, light microscopy. B. amphitrite is a common coastal barnacle, and is used as a model organism for studies into larval settlement. The free swimming larvae seen here are in the nauplius larval stage in which the thorax and abdomen have not developed yet. Nauplii larvae do not feed, but use internal yolk reserves from the egg for energy. Filmed with darkfield illumination.