English: Models of a Lion's Mane Jellyfish (Cyanea capillata) and a Thresher Shark (Alopias macrourus) at the Sant Hall of Oceans at the Smithsonian Museum of Natural History in Washington, D.C., USA.

The lion's mane jellyfish (Cyanea capillata) is the largest of all species of jellyfish. It lives in cold water, and has a lifespan of just a single year. They vary greatly in size, with smaller ones living in warmer waters (which has led some scientists to propose two sub-species rather than a single species). The bell can reach 8.2 feet (2.5 m) across, although smaller specimens have bells in the 20 inch (50 cm) range. The long, silvery tentacles can be anywhere from 30 feet to 100 feet (9.1 m to 30.5 m). They are very, very sticky, and are grouped into eight clusters of about a hundred each. Nearer the center of the lion's mane jellyfish is a mass of tangled, colored arms -- which gives the jelly its name (because this looks like a lion's mane). This mass is bright red in large specimens, but orange or tan in smaller ones. They feed on plankton, small fish, and other jellyfish. Their tentacles carry a poisonous toxin which can kill smaller animals, but which provides only a painful sting to human beings. Birds, large fish, and sea turtles are their primary predator.

Thresher sharks are found in the temperate and tropical oceans of the world. They prefer the open ocean, where they feed on bluefish, tuna, mackerel) squid, and cuttlefish. The tail is used to stun prey. They live to be about 20 years old, but breed infrequently. They are very prone to overfishing, and are not a threat to human beings.