Crystalline calcium phosphate and magnetic mineral content of Daphnia resting eggs.

Daphnia is a key crustacean zooplankton of freshwater food chains. One factor that ensures successful propagation is the Daphnia resting eggs, which are able to retain structural integrity under extreme conditions. Until recently little was known about the chemical composition, microanatomy, and physical properties of the egg itself. The current study demonstrates that the resting eggs: (1) have shells that are made up of crystalline calcium phosphate and include a honeycombed structure, and (2) contain magnetic material having properties consistent with magnetite. These properties of the resting eggs may ensure Daphnia survival in harsh environments.