Larvae plankton - Echinoderms
Echinoderms are marine animals and include the sea stars, brittle stars, sea urchins and sea cucumbers. The members are among the most familiar marine evertebrates and are largely bottom dwellers. All are relatively large animals and represent a group sharply distinguished from all other animals. They all have radial symmetry as adults.
The free -swimming larvae develop through different stages to the adult animal.