''Aurelia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of scyphozoan

jellyfish 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- ...

, commonly called moon jellies. There are currently 25 accepted species and many that are still not formally described. The genus was first described in 1816 by

Jean-Baptiste Lamarck Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck (; ), was a French naturalist, biologist, academic, and soldier. He was an early proponent of the idea that biologi ...

in his book ''Histoire Naturelle des Animaux sans Vertèbres'' (Natural History of Invertebrates). It has been suggested that ''Aurelia'' is the best-studied group of

gelatinous zooplankton Gelatinous zooplankton are fragile animals that live in the water column in the ocean. Their delicate bodies have no hard parts and are easily damaged or destroyed. Gelatinous zooplankton are often transparent. All jellyfish are gelatinous zoopla ...

, with ''

Aurelia aurita ''Aurelia aurita'' (also called the common jellyfish, moon jellyfish, moon jelly or saucer jelly) is a species of the genus ''Aurelia''. All species in the genus are very similar, and it is difficult to identify ''Aurelia'' medusae without geneti ...

'' the best-studied species in the genus; two other species, '' Aurelia labiata'' and '' Aurelia limbata'' were also traditionally investigated throughout the 20th century. In the early 2000s, studies that considered genetic data showed that diversity in ''Aurelia'' was higher than expected based solely on morphology, so one cannot confidently attribute the results from most of the previous studies to the species named. More recently, studies have highlighted the morphological variability (including the potential for

phenotypic plasticity Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompa ...

) in this genus, emphasizing the difficulty of identifying

cryptic species In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

. Species of ''Aurelia'' can be found in the Atlantic, Arctic, Pacific and Indian Oceans, and seem to be more common in

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

regions, such as in the waters off northern China, Japan, Korea, New Zealand, the northeastern and northwestern coasts of the United States as well as the northern Europe. ''Aurelia'' undergoes alternation of generations, whereby the sexually-reproducing pelagic medusa stage is either male or female, and the benthic polyp stage

reproduces asexually Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the fu ...

. Meanwhile, life cycle reversal, in which polyps are formed directly from juvenile and sexually mature medusae or their fragments, was also observed in '' Aurelia coerulea'' (= ''Aurelia'' sp. 1). Two moon jellyfishes at Sämstad

Appearance

The similar appearances of moon jellyfish is what has made them so hard to identify. They tend to have a variety of different sizes, however, they typically range from in diameter with an average of wide and in height. The polyps of these jellyfish can grow to tall and their ephyrae have an average diameter of . The adult medusae are typically translucent in color but the color of their gut can change based on what they eat; for example, if they eat crustaceans, they can have a pink or lavender tint to them and if they were to eat brine shrimp, the tint would be more of an orange color. Their polyps usually have around 16 tentacles (although
Aurelia insularia
' has 27-33 tentacles) which mostly help with feeding.

Feeding

The diet of ''Aurelia'' is similar to that of other jellyfish. They primarily feed on zooplankton. They may prey on or compete with commercially important fish and their larvae, as well as cause several issues for trawling boats when large aggregations occur, as they may clog and damage fishing nets as well as force fisherman to relocate.

Characteristics

They are able to sense light and dark and up and down due to

rhopalia Rhopalia (singular: rhopalium) are small sensory structures of certain Scyphozoan (true jellyfish) and Cubozoan (box jellyfish) species. Description The structures typically occur in multiples of four, are bell shaped and face outward from invagi ...

around the bell margin. After many tests on frogs, it was determined that ''A. aurita'' has a proteinaceous venom that causes muscle twitching by inducing the irreversible depolarization of the muscle membrane that is believed to be caused by an increase in the membrane’s permeability to sodium ions.

Reproduction

The medusa stage of the jellyfish reproduce sexually. The males release strings of sperm and the females ingest them. Once the ciliated larvae develop from the egg, they settle on or near the sea floor and develop into benthic polyps. The polyps then reproduce asexually and bud into ephyrae which later turn into medusae.

References

External links