Copepods dominate the zooplankton in nearly all areas of the World Ocean and thus play a significant role in the pelagic food web. Many copepod species feed mainly on phytoplankton and are important links between the primary producers and organisms of higher trophic levels. Accordingly, the knowledge of the impact of copepod grazing on phytoplankton stocks is essential for the understanding of particle and energy fluxes in the ocean.
Diatoms are generally known for superior mechanical properties of their mineralised shells. Nevertheless, many copepod crustaceans are able to crush such shells using their mandibles. This ability very likely requires feeding tools with specific material compositions and properties. For mandibles of several copepod species silica-containing parts called opal teeth have been described. The present study reveals the existence of complex composite structures, which contain, in addition to silica, the soft and elastic protein resilin and form opal teeth with a rubber-like bearing in the mandibles of the copepod Centropages hamatus. These composite structures likely increase the efficiency of the opal teeth while simultaneously reducing the risk of mechanical damage. They are supposed to have coevolved with the diatom shells in the evolutionary arms race, and their development might have been the basis for the dominance of the copepods within today's marine zooplankton.