ENVIRONMENT
Did you know that jellyfish are made up of 95% water and some species boast 24 eyes of varying ability? Naturalist Georgina Jones reveals more about these fascinating and beautiful creatures.
MARINE MEDUSAS
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each walkers coming across amorphous blobs of jellyfish washed up out of the ocean aren’t likely to think of imageforming eyes, symbiosis or energy efficient movement. Unless it’s associated with the plough snails enthusiastically scooting towards their prey. As it turns out though, some jellyfish have better eyesight than snails, and, apart from the inevitable exception to the group, the stalked jellyfish, have the most energy efficient movement in the animal kingdom. Rather impressive for brainless animals that are almost entirely composed of water. Jellyfish are made up of about 95% water and are related to corals, anemones and bluebottles. The standard body shape is a bell with tentacles,
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SEA RESCUE SPRING 2021
in various arrangements; and jellyfish mysteriously manage their lives without many of the physiological systems vertebrates depend on. Like blood, a heart or brains. Jellyfish have a radial nervous system or nerve net, dispersed throughout their bodies. This can smell, respond to stimuli such as food or danger, and detects light. They use heavy crystals on stalks to ensure these eye spots are always oriented towards the sky. Some specialist species, though, have no less than 24 eyes of varied abilities. While most jellyfish have only simple eyes capable of distinguishing between light and dark, box jellies that live in mangrove swamps have eyes that are capable
