Amphipods are the most abundant of free-swimming creatures in the deepest depths
Larvae: Although adult echinoderms (sea stars and kin) we are used to seeing have radial symmetry, their larvae start out with bilateral as do most vertebrates. These larval brittle stars are an important pelagic stage for dispersal of their bottom-bound parents. They capitalize on the abundance of food in the plankton to support early growth prior to metamorphosis and settlement to the sea floor.
Alexander Semenova - Arctic Biologist Shares Astonishing Sea Creatures With the World. (Lucernaria quadricornis)