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A jellyfish bloom is defined as a substantial increase in a jellyfish population within a short time period; the result of a higher reproduction rate. [2] Since jellyfish naturally have high reproductive rates, high-density blooms can occur as a result of both behavioral and ecological causes.
Stings may cause anaphylaxis (a form of shock), which can be fatal. Jellyfish kill 20 to 40 people a year in the Philippines alone. In 2006 the Spanish Red Cross treated 19,000 stung swimmers along the Costa Brava. [146] [147]
[6] [7] Marine jellyfish can consist of as much as 98% water, so are rarely found in fossil form. Unlike the hydrozoan jellyfish, Hydromedusae, Scyphomedusae lack a vellum, which is a circular membrane beneath the umbrella that helps propel the (usually smaller) Hydromedusae through the water.
Jellyfish are slow swimmers, and most species form part of the plankton. Traditionally jellyfish have been viewed as trophic dead ends, minor players in the marine food web, gelatinous organisms with a body plan largely based on water that offers little nutritional value or interest for other organisms apart from a few specialised predators such as the ocean sunfish and the leatherback sea turtle.
a Beroe ovata, b unidentified cydippid, c "Tortugas red" cydippid, d Bathocyroe fosteri, e Mnemiopsis leidyi, and f Ocyropsis sp. [17]. Among animal phyla, the ctenophores are more complex than sponges, about as complex as cnidarians (jellyfish, sea anemones, etc.), and less complex than bilaterians (which include almost all other animals).
Among the radiata, jellyfish and their kin, the main form of swimming is to flex their cup shaped bodies. All jellyfish are free-swimming, although many of these spend most of their time swimming passively. Passive swimming is akin to gliding; the organism floats, using currents where it can, and does not exert any energy into controlling its ...
The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when the bell pulsates. [11] As a result, box jellyfish can move more rapidly than other jellyfish; speeds of up to 6 metres (20 ft) per minute have been recorded. [12]
Cubozoa is a group commonly known as box jellyfish, that occur in tropical and warm temperate seas. They have cube-shaped, transparent medusae and are heavily-armed with venomous nematocysts. Cubozoans have planula larvae, which settle and develop into sessile polyps, which subsequently metamorphose into sexual medusae, [ 11 ] the oral end of ...