A Krill’s Life Cycle

A KRILL’S LIFECYCLE—Krill start life as eggs that sink and hatch in spring. They develop through larval stages as they swim back to the surface, reaching the fourth (furcilia) stage by winter. Krill that hatch at the depth of the Antarctic shelf (300-400 meters) can swim back to surface waters before winter and find phytoplankton to eat before they use up their stored supplies. Furcilia that make it survive their first winter by feeding on algae and zooplankton on the undersurface of pack ice. But krill that hatch in water deeper than 500 meters may starve before they can swim back to the surface, and food. (Illustration by Jayne Doucette, © Woods Hole Oceanographic Institution)