Earth’s Longest Creature Is a Brainless, Boneless Jellyfish With 1,200 Tentacles
The lion’s mane jellyfish (Cyanea capillata) is the longest known animal, with a bell up to about 2.1 meters and tentacles that can extend over 36 meters, longer than any other animal on Earth, though it has almost no mass compared with a blue whale. It is brainless and boneless, made mostly of seawater (~94%), and drifts with currents while its thousands of tentacles form a wide hunting net; the nematocysts on its tentacles fire in under 700 nanoseconds. This long-tentacled strategy is energetically cheap in cold Arctic waters, though it reduces propulsion efficiency by up to 80–90%. The species’ blooms are studied as indicators of ocean health and warming, contrasting with the blue whale’s massiveness but highlighting a different kind of “largest”—reach versus weight.
