The larval spider crab uses the numerous spines on its body to deter predators, but more importantly to increase its drag in the water to keep it from sinking, much like a parachute keeps its user in the air. 

Like other larval phases, it is important both as a dispersal phase, and to take advantage of the abundant food in the plankton. This tiny fellow is only millimetres in size.

Photo credit: CoML