And so, a larger story begins to emerge. The copepod and the planktivorous shark sometimes meet on the battlefield, munching side by side, and more often than not, the copepod is ingested by the big shark. Basking sharks do not have time to be too choosy about the odd copepod in their dinner. Nor do jellyfish, which have to wait for the unwary. Fish that are often not choosy—general feeders on whatever of the right size swims by or can be caught—thrive as larvae on plankton explosions and grow fat. And the predator sharks and the giant squid, of course, go in search of these fattened fish. Sperm whales go for the squid and a bit of fish, while killer whales, depending on their ecotype, focus on fattened fish, squid, sharks, including the white shark, and even the much larger blue whale, sperm whale and other whales. The dragonfish mostly take whatever they can get, whatever swims past or drifts down into the mid- to deep waters.
In far-flung areas of the ocean, the details of the story differ. While krill refers to dozens of species that provide food for fish, squid, ctenophores, penguins, seabirds, seals and whales, including the largest blue whales, large parts of the Antarctic ecosystem are utterly dependent upon a single krill species. A female Antarctic krill (Euphausia superba), about two to three inches (5–7.6 cm) long and filter-feeding on plankton, is very productive, laying 10,000 eggs several times a year. This krill lives all around the Antarctic in huge swarms of tens of thousands per cubic meter (264 gallons). The Antarctic krill emits bursts of blue bioluminescence from pairs of pivoting light organs along its body, each organ equipped with a lens and a reflector. It also has another pair of light organs on its eyestalks. Researchers Thérèse Wilson and Woody Hastings suggest that the bioluminescent flashing may allow the krill to keep in touch with one another. If so, this is a perfect situation for a hungry whale, seal or colossal squid. Blue whales, in particular, need concentrated prey to meet their energy requirements. Thus blue whales, perhaps navigating to this spot and calling across the ocean to other blues using the longest-range communication system on Earth, proceed to devour these ocean fireflies by the millions, grateful that a krill’s communication system works so conveniently to gather their dinner together.