Life at the Edge of the Sea

Barnacles are hermaphrodites, each individual acting as both male and female. A long penis is protruded and searches for a receptive barnacle. The penis is inserted and spermatozoa released into the mantle cavity of the receiving individual. Embryos are incubated in the mantle cavity before being released into the water as nauplius larvae. The nauplii spend 2-4 weeks floating in the plankton before metamorphosing and resettling on rocks.

This is a diagram of a nauplius larva, as it appears under the light microscope. The larva is translucent, and hence the internal organs can be seen. At this development stage, larvae are approximately 2mm long.