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Aurelia
Adult Aurelia medusa in the Red Sea
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Cnidaria
Class: Scyphozoa
Order: Semaeostomeae
Family: Ulmaridae
Genus: Aurelia
Lamarck, 1816
Synonyms[1]
  • Aurellia Péron & Lesueur, 1810
  • Ocyroe Péron & Lesueur, 1810

Aurelia is a genus of jellyfish that are commonly called moon jellies, which are in the class Scyphozoa. There are currently 25 accepted species and many that are still not formally described.[2][3][4]

The genus was first described in 1816 by Jean-Baptiste Lamarck in his book Histoire Naturelle des Animaux sans Vertèbres (Natural History of Invertebrates).[5] It has been suggested that Aurelia is the best-studied group of gelatinous zooplankton, with Aurelia aurita the best-studied species in the genus; two other species, Aurelia labiata and Aurelia limbata were also traditionally investigated throughout the 20th century.[6] In the early 2000s, studies that considered genetic data showed that diversity in Aurelia was higher than expected based solely on morphology,[7][8] 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[3] (including the potential for phenotypic plasticity[9][10]) in this genus, emphasizing the difficulty of identifying cryptic species.[11]

Species of Aurelia can be found in the Atlantic, Arctic, Pacific and Indian Oceans, and seem to be more common in temperate regions, such as in the waters off northern China, Japan, Korea, New Zealand, the northeastern and northwestern coasts of the United States, and those of northern Europe.[3]

Moon jellies differ from many jellyfish in that they lack long, potent stinging tentacles. Instead they have hundreds of short, fine tentacles that line the bell margin. The sting has a mild effect on humans, with most having little or no reaction.[12]

Aurelia undergoes alternation of generations, whereby the sexually-reproducing pelagic medusa stage is either male or female, and the benthic polyp stage reproduces asexually. 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).[13][not in body]

Description

[edit]
Two Aurelia aurita in Gullmarn fjord, Sweden

The similar appearances of moon jellyfish species is what has made them so hard to identify. They tend to have a variety of different sizes, however, they typically range 5–38 cm (2.0–15.0 in) in diameter with an average of 18 cm (7.1 in) wide and 8 cm (3.1 in) in height.[14][15] The polyps of these jellyfish can grow to 1.6 cm (0.63 in) tall and their ephyrae have an average diameter of 0.4 cm (0.16 in).[16]

The basic body plan of Aurelia consists of several parts. The animal lacks respiratory, excretory, and circulatory systems. The adult medusa of Aurelia, with a transparent look, has an umbrella margin membrane and tentacles that are attached to the bottom.[17] It has four bright gonads that are under the stomach.[17] The medusae are either male or female (gonochory).[14]

The adult medusae are typically translucent,[16] but the color of their gut can change based on what they eat; for example, if they eat certain crustaceans, they can have a pink or lavender tint to them; if they were to eat brine shrimp, the tint would be more of an orange color.[18] Their polyps usually have around 16 tentacles (although Aurelia insularia has 27–33 tentacles)[3][19] which mostly help with feeding.[16]

Physiology

[edit]
Aurelia with an anomalous number of gonads — most individuals have four.[17]

Aurelia does not have respiratory parts such as gills, lungs, or trachea; it respires by diffusing oxygen from water through the thin membrane covering its body. Within the gastrovascular cavity, low oxygenated water can be expelled and high oxygenated water can come in by ciliated action, thus increasing the diffusion of oxygen through the cell.[20] The large surface area membrane to volume ratio helps Aurelia diffuse more oxygen and nutrients into the cells.

Food travels through the muscular manubrium while the radial canals help disperse the food.[17] There is a middle layer of mesoglea, a gastrodervascular cavity with a gastrodermis, and an epidermis.[21] There is a nerve net that is responsible for contractions in swimming muscles and feeding responses.[14]

They are able to sense light and dark and up and down due to rhopalia around the bell margin.[15]

Venom

[edit]

Testing on frogs 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.[22]

Species

[edit]

The following species of Aurelia is accepted by the World Register of Marine Species:[1]

  • Aurelia sp. from the Monterey Bay Aquarium
    Aurelia sp. from the Monterey Bay Aquarium
  • A damaged Aurelia sp. individual
    A damaged Aurelia sp. individual
  • An adult Aurelia aurita
    An adult Aurelia aurita
  • On the beach
    On the beach
  • Aurelia aurita washed up on the beach, Jūrmala
    Aurelia aurita washed up on the beach, Jūrmala
  • Aurelia aurita at Ozeaneum Stralsund
    Aurelia aurita at Ozeaneum Stralsund

Distribution and habitat

[edit]

Aurelia species inhabit worldwide habitats.[23]It is found in the North, Black, Baltic and Caspian Seas, Northeast Atlantic, Greenland, northeastern USA and Canada, Northwest Pacific and South America.[3][24][25] In general, Aurelia is an inshore genus that can be found in estuaries and harbors.[17]

Moon jellyfish swimming (high resolution)

Aurelia live in ocean water temperatures ranging from 6–31 °C (43–88 °F); with optimum temperatures of 9–19 °C (48–66 °F). It prefers temperate seas with consistent currents. It has been found in waters with salinity as low as 6 parts per thousand.[26]

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.[27] 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 despite lower DO concentrations than normal.[27] 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 coastal waters such as Tokyo Bay in Japan and the Seto Inland Sea prove to be advantageous for the moon jellyfish in terms of feeding, growth, and survival.

Biology

[edit]
Aurelia aurita in Åbyfjorden, Sweden

The diet of Aurelia is similar to that of other jellyfish. They primarily feed on zooplankton.[15] Occasionally, they are also seen feeding on gelatinous zooplankton such as hydromedusae and ctenophores.[26]

The food is caught with its nematocyst-laden tentacles, tied with mucus, brought to the gastrovascular cavity, and passed into the cavity by ciliated action. There, digestive enzymes from serous cells break down the food. Little is known about the requirements for particular vitamins and minerals, but due to the presence of some digestive enzymes, we can deduce in general that Aurelia can process carbohydrates, proteins, and lipids.[14]

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.[28] 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,[29] as they may clog and damage fishing nets as well as force fisherman to relocate.[30]

A 2020 study found that Aurelia's body system is not significantly affected by artificial materials like microbeads, which can be found in cosmetic and personal care products. Aurelia aurita was able to recognize that microbeads were not food so there was not any physiological or histological harm.[31]

Three moon jellies captured by a lion's mane jellyfish

Aurelia have high proportions of polyunsaturated fatty acids compared to other prey types and are a source of vital nutrients for predators.[32] Aurelia are known to be eaten by a wide variety of predators, including the ocean sunfish (Mola mola), the leatherback sea turtle (Dermochelys coriacea), the scyphomedusa Phacellophora camtschatica,[33][34] and a very large hydromedusa (Aequorea victoria).[14] In 2016, it was reported from the Red Sea that Aurelia were seasonally preyed upon by two herbivorous fish.[35] Moon jellies are also fed upon by sea birds, which may be more interested in the amphipods and other small arthropods that frequent the bells of Aurelia, but in any case, birds do some substantial amount of damage to these jellyfish that often are found just at the surface of bays. Aurelia species have been suggested to have high mortality during the ephyra stage, which potentially affects the population size of the later medusa stage. While the main cause remains unknown, it is believed that they are consumed by one of three potential predatory filter-feeding sessile organisms: mussels, ascidians, and barnacles.[36]

Some metazoan parasites attack Aurelia, as well as most other species of jellyfish.[14]

Reproduction

[edit]
Aurelia aurita in Limfjord, Aalborg, Denmark

The medusa stage of the jellyfish reproduce sexually. The males release strings of sperm and the females ingest them.[18] 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.

The young larval stage, a planula, has small ciliated cells and after swimming freely in the plankton for a day or more, settles on an appropriate substrate, where it changes into a special type of polyp called a "scyphistoma", which divides by strobilation into small ephyrae that swim off to grow up as medusae.[37][38] There is an increasing size from starting stage planula to ephyra, from less than 1 mm in the planula stage, up to about 1 cm in ephyra stage, and then to several cm in diameter in the medusa stage.[17]

Aurelia jellyfish naturally die after living and reproducing for several months. It is probably rare for these moon jellies to live more than about six months in the wild, although specimens cared for in public aquarium exhibits typically live several to many years. In the wild, the warm water at the end of summer combines with exhaustive daily reproduction and lower natural levels of food for tissue repair, leaving these jellyfish more susceptible to bacterial and other disease problems that likely lead to the demise of most individuals. Such problems are responsible for the demise of many smaller species of jellyfish.[39] In 1997, it was summarized that seasonal reproduction leaves the gonads open to infection and degradation.[14]

A 2015 study has found that A. aurita are capable of life cycle reversal where individuals grow younger instead of older, akin to the "immortal jellyfish" Turritopsis dohrnii.[40]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Aurelia (cnidarian)

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from Grokipedia
Aurelia is a of scyphozoan belonging to the family , commonly known as moon jellyfish for their characteristic round, saucer- or dome-shaped bells that resemble the moon. These exhibit radial symmetry and are distinguished by a translucent, gelatinous bell typically measuring 5–40 cm in diameter, with a smooth to slightly scalloped margin divided into 8–16 lobes, numerous short marginal tentacles, and four frilly, unbranched oral arms surrounding the mouth. Prominent features include four interradial, horseshoe-shaped gonads visible through the bell's upper surface, which appear white in males and pinkish in females, along with a central manubrium and branching radial canals connected to a peripheral ring canal. The encompasses approximately 28 , many of which are cryptic and morphologically indistinguishable, necessitating molecular markers such as 16S rRNA and COI for accurate delimitation due to high intraspecific variability. Aurelia species have a , inhabiting coastal, neritic, and shelf seas worldwide across temperate to tropical latitudes, with some extending into polar regions, and tolerating temperatures from -6°C to 31°C and salinities as low as 0.6 PSU. They are often found in harbors, lagoons, and open waters near artificial structures, forming dense blooms influenced by factors like prey abundance, reduced predation from , and anthropogenic nutrient inputs. Ecologically, these are suspension feeders primarily consuming such as copepods, larval mollusks and , ciliates, and small hydrozoans, which they capture using nematocyst-laden tentacles and oral arms coated in adhesive mucus. In turn, they serve as prey for , sea turtles, and other medusae, while their blooms can disrupt fisheries, clog cooling systems, and alter microbial food webs through nutrient recycling. The life cycle of Aurelia is metagenic, featuring alternating sexual and across multiple stages: larva, benthic polyp, strobila, ephyra, and free-swimming . Adult medusae, which are gonochoric, release gametes into the water column for ; resulting settle on substrates like rocks or hulls to form polyps, which bud asexually and undergo strobilation to produce stacks of ephyrae that develop into mature medusae. This biphasic cycle enables rapid population proliferation, with polyps potentially surviving up to 25 years and medusae living 1–2 years, contributing to the genus's ecological success and occasional nuisance blooms.

Taxonomy

Classification

The genus Aurelia belongs to the phylum , class , subclass Discomedusae, order , and family . The taxonomic history of Aurelia traces back to 1758, when described the type species A. aurita (originally as Medusa aurita) in his , establishing it as the foundational taxon for the genus, which was formally named by in 1816. Over time, classifications have evolved with molecular data revealing cryptic diversity and refining species boundaries, though the core placement within has remained stable. Classification of Aurelia relies on key diagnostic traits shared with other semaeostome scyphozoans, including the absence of a true velum (distinguishing them from hydrozoans), the presence of eight marginal rhopalia (sensory clubs) equipped with statocysts for balance and orientation, and a bell margin featuring tentacle pits or chambers. These features, combined with molecular markers like 16S rRNA and COI, aid in delineating the genus amid morphological variability. Phylogenetically, Aurelia is nested within the subclass Discomedusae, the dominant of that excludes the more derived Coronatae, with molecular analyses supporting its alongside other ulmarid genera based on concatenated gene trees from mitochondrial and nuclear loci. This positioning highlights Aurelia's role in the broader scyphozoan radiation, where Discomedusae exhibit advanced medusan forms adapted to pelagic environments.

Diversity and Species

The genus Aurelia encompasses 30 accepted as of 2023, a count established through comprehensive taxonomic revisions incorporating molecular data post-2020. This expansion from earlier estimates of around 16 phylogenetic reflects advances in genetic analysis that have resolved cryptic diversity within what was long considered a single cosmopolitan . However, counts vary across taxonomic authorities; for example, the (WoRMS) recognizes fewer (~11 as of 2023) due to conservative acceptance criteria, underscoring the role of integrative molecular and morphological approaches in ongoing revisions. Among the notable species, (Linnaeus, 1758), the classic moon jellyfish, is the most widespread, occurring in temperate and subtropical coastal waters across multiple oceans. Aurelia coerulea (von Lendenfeld, 1884), known for its bluish hue, has gained attention as an in enclosed seas like the Mediterranean, where it forms dense blooms, though recent studies reassess its nonindigenous status. Other significant species include Aurelia limbata (Brandt, 1835), distinguished by its brownish bell margin and originally described from the , and Aurelia labiata (Chamisso & Eysenhardt, 1821), a Pacific representative with prominent oral arms. Species delineation in Aurelia primarily relies on molecular genetic markers, such as mitochondrial subunit I (COI) sequences, which reveal phylogenetic clusters otherwise indistinguishable by gross morphology. Complementary morphological traits include variations in shape—ranging from horseshoe to oval forms—and bell texture, such as the presence or absence of nematocyst batteries along the exumbrella. These criteria have been pivotal in distinguishing sibling . Recent taxonomic progress, driven by DNA barcoding efforts in the 2010s and culminating in integrative studies, has resulted in synonymies of outdated names and the elevation of regional variants to full species status, including the formal description of several new taxa based on type specimens from global collections. For instance, genetic analyses have confirmed distinct lineages in areas like the and Atlantic, previously lumped under A. aurita.

Morphology

External Features

The medusa stage of Aurelia species exhibits a distinctive bell morphology characterized by a saucer- or umbrella-shaped structure, with diameters typically ranging from 5 to 40 cm depending on the species and environmental conditions. The bell is primarily composed of a transparent, gelatinous layer comprising the majority of the bell's mass and consisting of over 95% water, providing buoyancy and structural support while maintaining a lightweight form. This is overlain by a thin , contributing to the overall translucent appearance of the bell. The surface of the bell features a generally smooth exumbrella, though the margin is often slightly scalloped with eight shallow indentations or notches that house the rhopalia—sensory structures essential for balance and light detection. Projecting from the subumbrella are four perradial oral arms, which are elongate, frilled, and lined with cilia along their edges, forming ciliated grooves that aid in prey manipulation. These arms extend below the bell in an X-shaped arrangement and are adorned with small, tentacle-like processes. Aurelia medusae display a translucent white or pale blue coloration, enhancing their ethereal visibility in coastal waters. Prominently visible through the bell are four horseshoe-shaped gonads situated in the gastric pouches, appearing pinkish in mature females and whitish in males due to differences in development. Species variations include a more rounded, hemispherical bell in A. aurita compared to the flatter profile of A. coerulea, reflecting subtle morphological adaptations across their distributions.

Internal Anatomy

The internal anatomy of Aurelia medusae is characterized by a decentralized organization lacking specialized organs for circulation, , or respiration, with physiological processes relying on and the gastrovascular cavity. Nutrients and gases are distributed via the branching gastrovascular system, which connects the central to radial canals extending into the bell margin. Waste products, including , diffuse directly across the thin epidermal and gastrodermal layers into the surrounding , facilitated by the acellular that forms the bulk of the bell's structure and acts as a permeable matrix. The consists of a diffuse without a centralized , comprising two primary networks: the motor nerve net (MNN) and the diffuse nerve net (DNN). The MNN, located primarily on the subumbrella surface, features large neurons with bipolar morphology that conduct impulses rapidly (0.45–1 m/s), coordinating bell contractions for locomotion. The DNN, sparser and slower-conducting (about 0.15 m/s), spans the subumbrella and margin, enabling finer control of radial movements and turns. Eight rhopalia, club-shaped sensory structures positioned at the bell margin between lappets, integrate sensory inputs and serve as pacemakers, linking the nerve nets through synaptic connections. Each houses specialized sensory components, including (lithocysts) for gravity detection and ocelli for phototaxis. The , an endodermal structure at the 's tip, contains lithocytes with crystalline statoliths that shift in response to orientation changes, stimulating mechanoreceptors to maintain balance and upright posture during swimming. Two ocelli per —a pigment-cup ocellus on the oral side for directional light sensing and a pigment-spot ocellus on the aboral side—enable shadow responses and modulation, influencing pulsing rates and vertical migration. These sensory functions allow Aurelia to orient toward light or avoid obstacles, with rhopalial neurons relaying signals to the DNN for behavioral adjustments. The muscular system is simplified, dominated by a monolayer of circular and radial muscle fibers embedded in the subumbrella , enabling without antagonistic muscles for relaxation. Contraction of the subumbrella circular muscles, innervated by the MNN, reduces bell volume and expels water through the velar opening, generating thrust via formation. Radial muscles at the margin, controlled by the DNN, facilitate asymmetric contractions for , while elastic recoil of the restores bell shape post-contraction. This system supports efficient, rhythmic pulsing at frequencies of 0.5–2 Hz, depending on size and environmental cues.

Life History

Reproduction

Aurelia species, such as A. aurita and A. coerulea, exhibit both sexual and asexual reproduction as part of their metagenetic life cycle, with sexual processes occurring in the medusa stage and asexual processes in the polyp stage. In sexual reproduction, mature medusae are dioecious, with separate male and female individuals releasing gametes into the surrounding water column for external fertilization. This process typically results in the formation of planula larvae, which are ciliated and free-swimming. Gonad development and maturation in medusae occur seasonally, often peaking in spring and summer when environmental conditions are favorable; for instance, in temperate regions, gonads appear in late April to early May, with full sexual maturity reached by summer, after which medusae devote significant energy to gamete production before senescence. Asexual reproduction predominates in the polyp stage and enables population expansion through multiple mechanisms, including , podocyst formation, and strobilation. Polyps produce new polyps via stolon budding (forming that develop into daughter polyps) or direct (outgrowths from the polyp body), as well as resting podocysts that can encyst and survive adverse conditions before excysting into new polyps. Strobilation involves the polyp segmenting transversely into a chain of ephyrae, the juvenile medusae, which detach and grow into mature medusae; this process is a key transition from to sexual phases. Recent research as of 2025 has demonstrated that the polyp plays a key role in regulating , including and strobilation, by influencing and environmental responses. These reproductive strategies are strongly influenced by environmental factors, particularly temperature, which modulates rates and modes of . For example, budding rates in polyps increase with higher temperatures (e.g., optimal at 14–21°C for A. coerulea), favoring budding under warmer, food-rich conditions, while podocyst production rises at elevated temperatures as a response. Strobilation is often triggered by specific temperature cues, such as a drop to 13–15°C in temperate waters, though some populations show flexibility. Warmer overall water temperatures promote polyp proliferation through enhanced budding, contributing to rapid population growth and subsequent medusa blooms in affected ecosystems.

Developmental Stages

The life cycle of Aurelia species, such as A. aurita, involves a metagenetic between a sexual phase and an asexual polyp phase, ensuring both dispersal and population persistence in varying environments. This alternation begins with fertilization of eggs released by mature medusae, producing embryos that develop into the first larval stage. The cycle progresses through distinct morphological and behavioral transitions, each adapted to specific ecological niches, from planktonic dispersal to benthic colonization and back to pelagic maturity. The stage represents the initial free-swimming larva, a ciliated, sausage-shaped form approximately 200–350 µm long and 110–150 µm wide, featuring an apical tuft of elongated cilia at the aboral pole for locomotion. Development from to competent takes about 4 days at 10–12 °C or up to 7 days at 22 °C, during which the differentiates into three compartments (aboral, middle, and oral) with specialized ultrastructures. These larvae exhibit phototactic behavior, typically positive phototaxis, and swim with the aboral pole forward, lasting 1–10 days in the before seeking suitable substrates for settlement. Upon attachment, the metamorphoses into the polyp stage, marking the shift to a benthic . The polyp stage, known as the scyphistoma, is a sessile, cylindrical form that attaches firmly to hard substrates such as rocks or artificial surfaces via a basal disc. Typically 2–5 mm in height, it possesses a crown of 16–24 hollow tentacles surrounding a for capturing small planktonic prey, which is digested in a simple gastrovascular cavity. Polyps can persist for months to years, undergoing through or to form colonies, which enhances survival during unfavorable conditions. This stage is foundational for population maintenance, as polyps serve as overwintering reservoirs before transitioning to the reproductive phase. Recent single-cell transcriptomic studies as of 2024 have elucidated molecular mechanisms driving the polyp-to-medusa transition, highlighting regulatory networks influenced by environmental cues. Strobilation initiates the asexual production of juvenile medusae, involving transverse horizontal fission of the polyp body into a stacked strobila under environmental cues such as a drop to 13–15 °C or shifts in food availability. The process unfolds over 5–12 days, starting with constrictions at the oral end and progressing downward, yielding 5–20 disc-shaped ephyrae per polyp; the native in polyps is essential for successful and ephyrae release during this phase. The ephyra stage consists of saucer-like, free-swimming juveniles, each approximately 2–5 mm in diameter, with eight arms and developing tentacles for active predation on . These ephyrae detach from the strobila and grow into adult e through gradual tissue expansion and segmentation, resorbing arm tissues as the bell margin expands outward over 1–2 months. Maturation to a fully formed medusa, with a bell up to 40 cm in diameter, takes an additional 4–6 months depending on temperature and nutrition, completing the cycle back to . This progression underscores the adaptive flexibility of Aurelia's metagenetic life history, balancing asexual proliferation with sexual dispersal.

Ecology

Feeding

Aurelia medusae are carnivorous predators that primarily consume planktonic crustaceans, particularly copepods such as Oithona davisae, which dominate their diet during periods of high abundance from spring to autumn. Larger individuals shift to include fish eggs, fish larvae, and small nektonic prey, while opportunistic on smaller conspecific medusae or ephyrae occurs when densities are high. Gut content analyses confirm these dietary preferences, with copepods comprising over 80% of identifiable prey in field samples from coastal waters. Prey capture relies on the extensive network of marginal tentacles and four oral arms, which are equipped with nematocysts—specialized stinging cells that discharge upon contact to paralyze and entangle small and larvae. Mucus secreted by the tentacles aids in , preventing escape, while the oral arms actively sweep prey toward the central . Ciliary currents generated by the bell's pulsations draw prey into range, and once ensnared, particles are transported via mucociliary tracts along the oral arms to the manubrium for ingestion. This passive-entrapment strategy allows Aurelia to efficiently exploit patchy distributions without rapid pursuit. Following , occurs extracellularly within the gastrovascular cavity, where glandular cells in the and gastric pouches secrete proteolytic enzymes that break down prey into soluble nutrients over approximately 1 hour at ambient temperatures. Undigested waste is expelled through the mouth, while absorbed nutrients are circulated via the four radial canals that extend from the central to the bell margin, facilitating to tissues throughout the . This compartmentalized process supports rapid nutrient uptake, enabling sustained growth in nutrient-variable environments. Daily rations vary with medusa size and prey availability, typically ranging from 0.6% to 5.6% of body carbon weight in natural populations, though laboratory studies indicate potential for higher consumption up to several times wet body weight under surplus conditions. Ingestion rates increase with predator size but show to prey density, saturating at moderate abundances to optimize energy gain.

Habitat and Distribution

Aurelia species exhibit a in coastal waters worldwide, spanning from to tropical regions in both the Northern and Southern Hemispheres, including the Atlantic, Pacific, and Indian Oceans. For instance, A. aurita is recorded in the North , , northwestern Pacific, and disjunct populations in , while other species like A. labiata occur along the Pacific coast of . This broad range reflects their adaptability to diverse marine environments, though recent phylogenetic studies indicate that what was once considered a single widespread species is actually a complex of multiple cryptic species with more restricted native distributions. These primarily inhabit neritic zones, from surface waters down to approximately 200 m depth, favoring coastal and shelf seas where they form seasonal blooms. They thrive in salinities ranging from 20 to 35 ppt and temperatures between 8 and 30°C, with optimal conditions around 9–19°C for A. aurita in temperate seas. Polyps, the sessile stage, attach to hard substrates such as rocks, piers, , shells, or artificial structures like and PVC in intertidal to shallow subtidal areas (0.1–3 m), often in sheltered bays with macroalgal cover. Certain Aurelia species demonstrate invasive potential in non-native regions, facilitated by human activities like shipping. A. coerulea, native to the northwest Pacific, has established populations in the (e.g., harbors in , , and ) and the through ballast water transport and aquaculture trade, leading to blooms in these enclosed basins.

Ecological Role

Aurelia species occupy a pivotal position in marine food webs as both predators and prey. As predators, they exert significant control over populations, particularly copepods, by consuming substantial quantities that can reduce prey densities by up to 73% within aggregations, thereby influencing trophic cascades and potentially increasing levels due to diminished grazing pressure. As prey, Aurelia medusae serve as a source for a variety of higher trophic levels, including sea turtles such as the leatherback (Dermochelys coriacea), various like and , and seabirds, which helps transfer energy upward in the pelagic ecosystem. Blooms of Aurelia, characterized by rapid population surges, are facilitated by the of their polyp stage through and strobilation, allowing exponential increases in numbers under favorable conditions like high food availability. These blooms can disrupt fisheries by competing with for and damaging gear, while also clogging cooling intakes at coastal power plants, leading to operational shutdowns. Recent research has revealed that the jellyfish's associated plays a key role in its life cycle, with microbiota-derived required for the strobilation process in polyps, thereby influencing production and population proliferation. exacerbates Aurelia's ecological dynamics by warming ocean temperatures, which promote earlier strobilation, higher production rates, and range expansions into previously cooler regions, thereby increasing bloom frequency and intensity. activities intersect with these blooms through conflicts in coastal zones, where dense aggregations sting beachgoers and deter , while fouling aquaculture net pens and causing gill damage or mortality in farmed . Although Aurelia lack major conservation designations due to their widespread abundance, they are monitored for potential invasiveness in altered ecosystems driven by anthropogenic pressures.

References

  1. https://invasions.si.edu/nemesis/species_summary/-265
  2. https://sta.uwi.edu/fst/lifesciences/sites/default/files/lifesciences/images/Aurelia%20aurita%20-%20Moon%20Jellyfish.pdf
  3. https://pmc.ncbi.nlm.nih.gov/articles/PMC8435205/
  4. https://www.sciencedirect.com/science/article/abs/pii/S0305197815000654
  5. https://sites.cs.ucsb.edu/~xyan/papers/nature18_gold.pdf
  6. https://www.marinespecies.org/aphia.php?p=taxdetails&id=135263
  7. https://www.marinespecies.org/aphia.php?p=taxdetails&id=135306
  8. https://animaldiversity.org/accounts/Scyphozoa/
  9. https://onlinelibrary.wiley.com/doi/10.1111/brv.12393
  10. https://peerj.com/articles/11954/
  11. https://www.mdpi.com/1424-2818/15/12/1181
  12. https://bmcecolevol.biomedcentral.com/articles/10.1186/1471-2148-2-1
  13. https://www.marinespecies.org/aphia.php?p=taxdetails&id=135308
  14. https://www.marinespecies.org/aphia.php?p=taxdetails&id=135307
  15. https://europeanjournaloftaxonomy.eu/index.php/ejt/article/view/230
  16. https://doi.org/10.5962/bhl.title.5996
  17. https://lanwebs.lander.edu/faculty/rsfox/invertebrates/aurelia.html
  18. https://doi.org/10.1111/zoj.12494
  19. https://www.marlin.ac.uk/species/detail/2089
  20. https://pmc.ncbi.nlm.nih.gov/articles/PMC6999044/
  21. https://pmc.ncbi.nlm.nih.gov/articles/PMC2706374/
  22. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0098310
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