Aurelia aurita
Encyclopedia
Aurelia aurita is one of a group of more than ten morphologically nearly identical jellyfish
species in the genus
Aurelia
. In general, it is nearly impossible to identify Aurelia medusae without genetic sampling, so most of what follows about Aurelia aurita, could equally be applied to any species of the genus. The medusa is translucent, usually about 25–40 cm in diameter, and can be recognized by its four horseshoe-shaped gonads that are easily seen through the top of the bell. It feeds by collecting medusae, plankton
and mollusks with its mucusy bell nematocyst-laden tentacles and bringing the prey into its body for digestion, but is capable of only limited motion; like other jellies it primarily drifts with the current, even when it is swimming.
to as far north as latitude 70°N
and as far south as 40°S
. The species Aurelia aurita, whose distribution has been confirmed by Michael Dawson using genetic analysis, 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 harbor
s. It lives in ocean
water temperatures ranging from 6 °C to 31 °C; with optimum temperatures of 9 °C to 19 °C. A. aurita prefers temperate seas with consistent currents. It has been found in waters with salinity
as low as 6 parts per thousand.
enzymes from serous cell break down the food. There is little known about the requirements for particular vitamins and minerals, but due to the presence of some digestive enzymes, we can deduce in general that A. aurita can process carbohydrates, proteins and lipids.
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Higher magnification showing a prey item, probably a copepod
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The prey is then drawn to the body by contracting the tentacles in a corkscrew fashion (image taken with an ecoSCOPE
).
parts such as gill
s, lung
s, or trachea
. Since it is a small organism, it respires by diffusing
oxygen from water through the thin membrane. 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 cell. The large surface area membrane to volume ratio helps Aurelia to diffuse more oxygen and nutrients into the cells.
The basic body plan of Aurelia consists of several parts. The animal lacks respiratory, excretory
, and circulatory system
s. The adult medusa of Aurelia, with a transparent look, has an umbrella margin membrane and tentacles that are attached to the bottom. It has four bright circular gonad
s that are under the stomach. Food travels through the muscular manubrium
while the radial canals help disperse the food. There is a middle layer of mesoglea
, gastrodervascular cavity with gastrodermis
, and epidermis
. There is a nerve
net that is responsible for contractions in swimming muscles and feeding responses. Adult medusa can have a diameter up to 40 cm.
The medusae are either male or female. 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 ephyra
e that swim off to grow up as medusae
. 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.
(Mola mola), the Leatherback Sea Turtle
(Dermochelys coriacea), the scyphomedusa Phacellophora camtschatica, and a very large hydromedusa (Aequorea victoria
). 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 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. In 1997, Arai summarized that seasonal reproduction leaves the gonads open to infection and degradation.
Some metazoan parasites attack Aurelia aurita, as well as most other species of jellyfish.
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
species in the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Aurelia
Aurelia (genus)
Aurelia is a genus of scyphozoan jellyfish . There are at least 13 species in the genus Aurelia including many that are still not formally described...
. In general, it is nearly impossible to identify Aurelia medusae without genetic sampling, so most of what follows about Aurelia aurita, could equally be applied to any species of the genus. The medusa is translucent, usually about 25–40 cm in diameter, and can be recognized by its four horseshoe-shaped gonads that are easily seen through the top of the bell. It feeds by collecting medusae, plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
and mollusks with its mucusy bell nematocyst-laden tentacles and bringing the prey into its body for digestion, but is capable of only limited motion; like other jellies it primarily drifts with the current, even when it is swimming.
Distribution
Genus Aurelia is found throughout most of the world's oceans, from the tropicsTropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
to as far north as latitude 70°N
70th parallel north
The 70th parallel north is a circle of latitude that is 70 degrees north of the Earth's equatorial plane, in the Arctic. It crosses the Atlantic Ocean, Europe, Asia and North America, and passes through some of the southern seas of the Arctic Ocean....
and as far south as 40°S
40th parallel south
The 40th parallel south is a circle of latitude that is 40 degrees south of the Earth's equatorial plane. It crosses the Atlantic Ocean, the Indian Ocean, Australasia, the Pacific Ocean and South America....
. The species Aurelia aurita, whose distribution has been confirmed by Michael Dawson using genetic analysis, 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
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
and harbor
Harbor
A harbor or harbour , or haven, is a place where ships, boats, and barges can seek shelter from stormy weather, or else are stored for future use. Harbors can be natural or artificial...
s. It lives in ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
water temperatures ranging from 6 °C to 31 °C; with optimum temperatures of 9 °C to 19 °C. A. aurita prefers temperate seas with consistent currents. It has been found in waters with salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
as low as 6 parts per thousand.
Feeding
A. aurita and other Aurelia species feed on plankton that includes organisms such as mollusks, crustaceans, tunicate larvae, rotifers, young polychaetes, protozoans, diatoms, eggs, fish eggs, and other small organisms. Occasionally, they are also seen feeding on gelatinous zooplankton such as hydromedusae and ctenophores. Both the adult medusae and larvae of Aurelia have nematocysts to capture prey and also to protect themselves from predators. The food is tied with mucus, and then it is passed down by ciliated action down into the gastrovascular cavity where digestiveDigestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....
enzymes from serous cell break down the food. There is little known about the requirements for particular vitamins and minerals, but due to the presence of some digestive enzymes, we can deduce in general that A. aurita can process carbohydrates, proteins and lipids.
Filtering Grid of Tentacles on the Bell Margin
 |
High resolution in situ image of an undulating live Aurelia in the Baltic Baltic Sea The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and... showing the grid of tentacles which are slowly pulled through the water. The motion is so slow that copepods can not sense it and don't react with an escape response Escape response Escape response, escape reaction, or escape behaviour is a possible reaction in response to stimuli indicative of danger, in particular, it initiates an escape motion of an animal... |
Higher magnification showing a prey item, probably a copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
The prey is then drawn to the body by contracting the tentacles in a corkscrew fashion (image taken with an ecoSCOPE
EcoSCOPE
The ecoSCOPE is an optical sensor system, deployed from a small remotely operated vehicle or fibre optic cable, to investigate behavior and microdistribution of small organisms in the ocean.-Deployment:...
).
Body system
Aurelia does not have respiratoryRespiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
parts such as gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s, lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s, or trachea
Invertebrate trachea
The invertebrate trachea refers to the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues....
. Since it is a small organism, it respires by diffusing
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
oxygen from water through the thin membrane. 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 cell. The large surface area membrane to volume ratio helps Aurelia to diffuse more oxygen and nutrients into the cells.
The basic body plan of Aurelia consists of several parts. The animal lacks respiratory, excretory
Excretion
Excretion is the process by which waste products of metabolism and other non-useful materials are eliminated from an organism. This is primarily carried out by the lungs, kidneys and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell...
, and circulatory system
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
s. The adult medusa of Aurelia, with a transparent look, has an umbrella margin membrane and tentacles that are attached to the bottom. It has four bright circular gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s that are under the stomach. Food travels through the muscular manubrium
Manubrium
The manubrium or manubrium sterni is the broad, upper part of the sternum. Located ventrally with a quadrangular shape, wider superiorly and narrower inferiorly, it articulates with the clavicles and the first two ribs.-Borders:The superior border is the thickest and presents at its center the...
while the radial canals help disperse the food. There is a middle layer of mesoglea
Mesoglea
Mesoglea is the translucent, inert, jelly-like substance that makes up most of the bodies of jellyfish, comb jellies and certain primitive sea creatures in the phyla Cnidaria and Ctenophora. It acts as the creatures' structural support in water, as they lack bones or cartilage, endo- or...
, gastrodervascular cavity with gastrodermis
Gastrodermis
The gastrodermis is the inner layer of cells that lines a gastrovascular cavity of Cnidarians....
, and epidermis
Squamous epithelium
In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous epithelial cells...
. There is a nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
net that is responsible for contractions in swimming muscles and feeding responses. Adult medusa can have a diameter up to 40 cm.
The medusae are either male or female. The young larval stage, a planula
Planula
A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species. The planula forms from the fertilized egg of a medusa, as the case in scyphozoans and some hydrozoans, or from a polyp, as in the case of anthozoans...
, has small ciliated cells and after swimming freely in the plankton for a day or more, settles on an appropriate substrate
Substrate (marine biology)
Stream substrate is the material that rests at the bottom of a stream. There are several classification guides. One is:*Mud – silt and clay.*Sand – Particles between 0.06 and 2 mm in diameter.*Granule – Between 2 and 4 mm in diameter....
, where it changes into a special type of polyp
Polyp
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are approximately cylindrical in shape and elongated at the axis of the body...
called a "scyphistoma", which divides by strobilation
Strobilation
Strobilation or transverse fission is a form of asexual reproduction consisting of the spontaneous transverse segmentation of the body. It is observed in certain cnidarians and helminths...
into small ephyra
Ephyra
Ephyra may refer to:* The city of Kichyro, later known as Ephyra.* Ephyra, one of the Oceanids* Ephyra, one of the Nereids* Ephyra, a stage of the life cycle of jellyfish* Efyra, a village and an archeological site in Elis, Greece...
e that swim off to grow up as medusae
Medusa (biology)
In biology, a medusa is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below...
. 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.
Predators
Aurelia aurita is known to be eaten by a wide variety of predators including the Ocean SunfishOcean sunfish
The ocean sunfish, Mola mola, or common mola, is the heaviest known bony fish in the world. It has an average adult weight of . The species is native to tropical and temperate waters around the globe. It resembles a fish head with a tail, and its main body is flattened laterally...
(Mola mola), the Leatherback Sea Turtle
Leatherback Sea Turtle
The leatherback sea turtle is the largest of all living sea turtles and the fourth largest modern reptile behind three crocodilians. It is the only living species in the genus Dermochelys. It can easily be differentiated from other modern sea turtles by its lack of a bony shell. Instead, its...
(Dermochelys coriacea), the scyphomedusa Phacellophora camtschatica, and a very large hydromedusa (Aequorea victoria
Aequorea victoria
Aequorea victoria, also sometimes called the crystal jelly, is a bioluminescent hydrozoan jellyfish, or hydromedusa, that is found off the west coast of North America. This species is thought to be synonymous with Aequorea aequorea of Osamu Shimomura, the discoverer of green fluorescent protein . ...
). 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 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. In 1997, Arai summarized that seasonal reproduction leaves the gonads open to infection and degradation.
Some metazoan parasites attack Aurelia aurita, as well as most other species of jellyfish.
Gallery
Further reading
- Moen, F.E. and E. Svensen. 2004. Marine fish & invertebrates of Northern Europe. AquaPress: Southend-on-Sea. ISBN 0-9544060-2-8. 608 pp.
- National Center for Biotechnology Information. October 23, 2001. http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi