It's still not clear which came first, polyps or medusae, but jellyfish have floated around for millennia and withstood the onset and extinction of many other pelagic orders. Even in a world of anthropogenic climatic change, scyphozoans are expected to thrive, as their predators suffer the double whammy of hotter oceans and inhuman appetites.
Typical jellyfish are bells of gelatinous tissue that propel a dangle of tentacles, a ring of fire laced with stinging cells and venom powerful enough to stun fish or scar face. But one family has retraced the route of sessile polyps and discovered the attractions of life in the shallow end. Cassiopeids still sting, albeit to little effect, but these former hunters have acquired cellmates that allow the jellyfish to live easy, lying on their backs and basking on flats between coral reefs and mangrove swamps. The latter also provide homes for young medusae and this may account for the seasonal abundance of the animals around Pulau Semakau, where the jellyfish share the seagrass with fellow harvesters of light. In the Caribbean, cycles of blooms and bust have been reported and traced to nutrient spikes from nearby settlements. Only minor explosions of orange ribbons affect local waters, which in their lack of clarity may offer Cassiopea little room for expansion. Perhaps half-a-century of dredgery was enough to hold back a tide of drifters from overwhelming a bed of more rugged blooms.
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