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Upside-Down Jellyfish Video Stock Footage
The medusa phase of Cassiopea xamachana can grow to a diameter of about 25 cm (10 in). Compared to most species of jellyfish it is upside-down, that is to say the bell, which is saucer-shaped, is underneath and acts like a suction cup to stabilise the jellyfish on the seabed. The four pairs of much-branched tentacles are on the upperside. Instead of a central mouth, there are numerous oral openings in the tentacles which connect via channels to the stomach. The mesogloea, the jelly-like tissue, contains symbiotic zooxanthellae, single-celled protists, which are photosynthetic and give the jellyfish its variable color, often bluish-grey or bluish-green. The life cycle of Cassiopea xamachana alternates between a polyp phase and the medusa phase. Gametes are released by the medusae into the water and the fertilized eggs hatch into planula larvae, which attach to the sea bed or some other suitable substrate. Decomposing red mangrove (Rhizophora mangle) give off a substance which attracts the larvae to settle. Having settled, the larvae undergo metamorphosis into the hydroid stage of the lifecycle, forming tiny sessile polyps called scyphistomae. Under favorable conditions these bud and form further scyphistomae. In due course, when they have acquired zooxanthellae and the temperature exceeds 20 °C (68 °F), these strobilate (split) and new medusae are formed. In Florida, the medusae are found all the year round but the scyphistomae are only present in la...
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