The longest animal on Earth, Cyanea capillata, has been named as the lion’s mane jellyfish, which measures 2.1 meters (7 feet) across and stretches 36.6 meters (120 feet) behind it, longer than any other animal on earth. The species was discovered in 1865 on a Massachusetts beach and still holds the record for longest length. The length of the lion's mane's tentacles is not coincidental as it is a passive hunter, relying heavily on ocean currents to travel distances. However, this has a mechanical cost, as research suggests that having extensive tentacles and oral arms can reduce a jellyfish’�s propulsion efficiency by up to 90% compared to a tentacle-free state. The lion‘s bell is divided into eight lobes, with each lobe containing roughly 70 to 150 tentacles arranged in four rows. In a large adult, these tentacles can number over 1,000 in total, each of which is lined with stinging cells known as nematocysts. Despite these adaptations, they also make it a significantly worse swimmer. The animal's structure allows it to grow to the larger size and is often used as a diagnostic tool for climate change.