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The Irukandji jellyfish (/ ɪr ə ˈ k æ n dʒ i / irr-ə-KAN-jee) are any of several similar, extremely venomous species of rare box jellyfish. With a very small adult size of about a cubic centimetre (1 cm 3 or 0.061 in 3 ), they are both one of the smallest and one of the most venomous jellyfish in the world.
Turritopsis dohrnii, also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish [2] [3] found worldwide in temperate to tropic waters. It is one of the few known cases of animals capable of completely reverting to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual.
M. virulenta is one of the largest species of box jellyfish, with tentacle lengths of about three metres at maximum extension. The maximum bell height observed in M. virulenta can range up to 250 mm and the bell width can range up to 200 mm. [ 3 ] The bell of M. virulenta is rectangle-shaped and covered with nematocyst warts.
The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years, [1] and possibly 700 million years or more, making them the oldest multi-organ animal group. [2]
Whereas some other jellyfish have simple pigment-cup ocelli, box jellyfish are unique in the possession of true eyes, complete with retinas, corneas and lenses. [13] Their eyes are set in clusters at the ends of sensory structures called rhopalia which are connected to their ring nerve. Each rhopalium contains two image-forming lens eyes.
Copula is a monotypic genus of box jellyfish in the family Tripedaliidae of the phylum Cnidaria. The only species in the genus is Copula sivickisi, a very small gelatinous, bell-shaped jellyfish with four tentacles that is active only at night. It is unusual among box jellyfish in having a mating ritual and internal fertilization.
The jellyfish measure about 8 inches (20 centimeters) in length. A rock slab shows one large (right) and one small (left) bell-shaped jellyfish with tentacles. The smaller animal is rotated 180 ...
Giant phantom jellyfish live in every ocean except for the Arctic Ocean. However, because they typically swim deep below the surface, they are hardly seen by humans. Daniel M. Moore noted that one potential explanation is that the jellyfish swim higher up to expose themselves to ultraviolet radiation, which will rid them of parasites. Another ...