Moon jellyfish
| Aurelia aurita | |
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| Aurelia aurita, Red Sea | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Scyphozoa |
| Order: | Semaeostomeae |
| Family: | Ulmaridae |
| Genus: | Aurelia |
| Species: | A. aurita |
| Binomial name | |
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Aurelia aurita Linnaeus, 1758 |
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Aurelia aurita (also called the common jellyfish, moon jellyfish, moon jelly, or saucer jelly) is a widely studied species of the genus Aurelia. All species in the genus are closely related, and it is difficult to identify Aurelia medusae without genetic sampling; most of what follows applies equally to all species of the genus.
The jellyfish is translucent, usually about 25–40 cm (10–16 in) in diameter, and can be recognized by its four horseshoe-shaped gonads, easily seen through the top of the bell. It feeds by collecting medusae, plankton, and mollusks with its tentacles, and bringing them into its body for digestion. It is capable of only limited motion, and drifts with the current, even when swimming.
The genus Aurelia is found throughout most of the world's oceans, from the tropics to as far north as latitude 70°N and as far south as 40°S. The species Aurelia aurita is found along the eastern Atlantic coast of Northern Europe and the western Atlantic coast of North America in New England and Eastern Canada. In general, Aurelia is an inshore genus that can be found in estuaries and harbors.
A. aurita lives in ocean water temperatures ranging from 6 to 31 °C (43 to 88 °F); with optimum temperatures of 9 to 19 °C (48 to 66 °F). It prefers temperate seas with consistent currents. It has been found in waters with salinity as low as 6 parts per thousand. The relation between summer hypoxia and moon jellyfish distribution is prominent during the summer months of July and August where temperatures are high and dissolved oxygen (DO) is low. Of the three environmental conditions tested, bottom DO has the most significant effect on moon jellyfish abundance. Moon jellyfish abundance is the highest when bottom dissolved oxygen concentration is lower than 2.0 mg L -1. Moon jellyfish show a strong tolerance to low DO conditions, which is why their population is still relatively high during the summer. Generally, hypoxia causes species to move from the oxygen depleted zone, but this is not the case for the moon jellyfish. Furthermore, bell contract rate, which indicates moon jellyfish feeding activity, remains constant although DO concentrations are lower than normal. During July and August it is observed that moon jellyfish aggregations of 250 individuals consumed an estimated 100% of the mesozooplankton biomass in the Seto Inland Sea. Other major fish predators that are also present in these coastal waters do not seem to show the same high tolerance to low DO concentrations that the moon jellyfish exhibit. The feeding and predatory performance of these fish significantly decreases when DO concentrations are so low. This allows for less competition between the moon jellyfish and other fish predators for zooplankton. Low DO concentrations in the coastal waters such as the Tokyo Bay in Japan and Seto Inland Sea prove to be advantageous for the moon jellyfish in terms of feeding, growth, and survival.
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Wikipedia