page_title: Jellyfish
section_title: Largest and smallest
hierarchical_section_title: Jellyfish / Largest and smallest
caption_attribution_description: A Lion's mane jelly. Photo by Dan Hershman.
context_page_description: Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are not mobile, being anchored to the seabed by stalks. The bell can pulsate to provide propulsion and highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, the planula larva can disperse widely and is followed by a sedentary polyp phase.
  Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast growing, mature within a few months and die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived.
context_section_description: Jellyfish range from about one millimeter in bell height and diameter, to nearly 2 metres (7 ft) in bell height and diameter; the tentacles and mouth parts usually extend beyond this bell dimension.
  The smallest jellyfish are the peculiar creeping jellyfish in the genera Staurocladia and Eleutheria, which have bell disks from 0.5 millimetres (¹⁄₃₂ in) to a few millimeters in diameter, with short tentacles that extend out beyond this, which these jellyfish use to move across the surface of seaweed or the bottoms of rocky pools. Many of these tiny creeping jellyfish cannot be seen in the field without a hand lens or microscope; they can reproduce asexually by fission (splitting in half). Other very small jellyfish, which have bells about one millimeter, are the hydromedusae of many species that have just been released from their parent polyps; some of these live only a few minutes before shedding their gametes in the plankton and then dying, while others will grow in the plankton for weeks or months. The hydromedusae Cladonema radiatum and Cladonema californicum are also very small, living for months, yet never growing beyond a few mm in bell height and diameter.
  The lion's mane jellyfish, Cyanea capillata, was long-cited as the largest jellyfish, and arguably the longest animal in the world, with fine, thread-like tentacles that may extend up to 36.5 m (119 ft 9 in) long (though most are nowhere near that large). They have a moderately painful, but rarely fatal, sting.
  The increasingly common giant Nomura's jellyfish, Nemopilema nomurai, found in some, but not all years in the waters of Japan, Korea and China in summer and autumn is another candidate for "largest jellyfish", in terms of diameter and weight, since the largest Nomura's jellyfish in late autumn can reach 2 m (6 ft 7 in) in bell (body) diameter and about 200 kg (440 lb) in weight, with average specimens frequently reaching 0.9 m (2 ft 11 in) in bell diameter and about 150 kg (330 lb) in weight. The large bell mass of the giant Nomura's jellyfish can dwarf a diver and is nearly always much greater than the Lion's Mane, whose bell diameter can reach 1 m (3 ft 3 in).
  The rarely encountered deep-sea jellyfish Stygiomedusa gigantea is another candidate for "largest jellyfish", with its thick, massive bell up to 100 cm (3 ft 3 in) wide, and four thick, "strap-like" oral arms extending up to 6 m (20 ft) in length, very different from the typical fine, threadlike tentacles that rim the umbrella of more-typical-looking jellyfish, including the Lion's Mane.
caption: The lion's mane jellyfish (Cyanea capillata) is one of the largest species.
exif: {}