How Jellyfish Vanish into Thin Air

By late August, even the most diehard summer lovers (myself included) are getting a little tired of the heat. But while the heat may sap our energy and make us spend more time indoors, it’s only an inconvenience. For jellyfish, it’s a whole different story.

Along many coastlines, jellyfish, starfish, anemones and small fish become trapped in shallow pools of water when the tide recedes. On hot summer days these tide pools look calm and sparkling, but for jellyfish caught in them, they can be devastating. Composed of about 95% water, delicate jellyfish start to quickly lose moisture when the shallow pools are warmed by the sun. Without shells, scales, or any real protection, their soft, transparent bodies shrink and wither until there’s little left but a faint trace of salt on the sand. They can literally evaporate before our eyes.

While excessive exposure to sunlight can be deadly, the sun is essential to life for many jellyfish. Several species engage in a symbiotic relationship with microscopic algae called zooxanthellae. These organisms reside within the jellyfish’s tissues like tiny solar panels. Through photosynthesis, the algae convert sunlight into energy, producing sugars that nourish the jellyfish. In return, the jellyfish provide the algae with a safe environment and access to sunlight.

More interesting facts about jellyfish: They’re not fish at all, but are actually plankton, ranging in size from less than an inch to nearly eight feet long, with tentacles that can measure an amazing 100 feet or more. The largest jellyfish is longer than a blue whale, the largest of all whale species. Jellyfish have no bones, no brain and no heart. Sensory nerves at the base of their tentacles enable them to detect light and odors.