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Phronima Female and Young

A translucent, female hyperiid surrounded by white young in a barrel-shaped body cavity.
K.J. Osborn

This female hyperiid (Phronima sedentaria) is surrounded by her young, residing in the hollowed out barrel-shaped body cavity of a salp. It is thought that the mother Phronima captures and kills the salp to build a nursery. She lays her eggs inside and then paddles it around while caring for her young. 

Phronima eyes see blue light best and are well-suited to look for other animals horizontally from the inside of their barrel. They use large appendages to hold onto the sides of the salp and to steer its movement through the water.