Geographic Range
Moon jellies inhabit the coastal regions of the Pacific Ocean from San Diego, California,
to Prince William Sound, Alaska. Though
Aurelia labiata
has been identified solely in this Eastern region of the Pacific Ocean, its close
relative
A. aurita
is a cosmopolitan species that is ecountered in coastal waters around the world.
Confusion in identifying the two species may distort the true range of the moon jellies.
- Biogeographic Regions
- nearctic
Habitat
Moon jellies float near the surface in warm nearshore waters and are especially prevalent
in bays and harbors, such as the Monterey Bay. Though common in coastal regions,
moon jellies have been referred to as pelagic, or living in the open waters of the
ocean. An extremely close relative to
A. labiata
,
A. aurita
can survive in waters ranging from -6 to 31 degrees Celsius. It is very likely that
A. labiata
tolerates similar temperature ranges.
- Habitat Regions
- temperate
- saltwater or marine
Physical Description
The translucent, moonlike bell that is characteristic of
Aurelia labiata
has earned moon jellies their common name. They do not have the long trailing tentacles
that people usually associate with jellyfish. Instead, they have a fine fringe lining
the bell margin. The body form of
A. labiata
is distinguished from close relatives in the genus
Aurelia
by an enlarged, fleshy manubrium, four oral arms protruding from the base of the
manubrium, planulae (ciliated fertilized egg) brooding on the manubrium, and secondary
scalloping of the bell margin between rhopalia, forming 16 notches.
Aurelia labiata
ranges from 100 mm to 450 mm. Bells of juveniles and young adults are translucent,
and with maturity they turn milky white, sometimes with a pink, purple, peach, or
blue tint.
Aurelia labiata can easily be divided into three geographical morphotypes. The southernmost form, found in California from San Diego to Marina del Ray, has a manubrium that is a wide, rounded frill. The radial canals range in number, depending on age. The oral arms are typically straight. Planulae range in color from white to bright orange, and the bells are colorless to milky white. Male gonads are dark purple, and female gonads are pale pink. Southern moon jellies grow to a maximum of 35 cm.
The central form inhabits coastal waters from Santa Barbara, California, to Newport, Oregon. Abundant in late summer, central moon jellies have an elongated manubrium that is rectangular and tapering. The radial canals are very numerous, and the oral arms are straight or bent counter-clockwise. The planulae are lavender, and medusae found in Monterey, California, are usually purple, while those found in Santa Barbara are often pale pink. Male gonads are dark purple, and female gonads are brown. Individuals of the central form of A. labiata have been recorded as high as 45 cm.
The northernmost form, ranging from Puget Sound, Washington, to Prince William Sound,
Alaska, have a pyramidal manubrium. The many parallel radial canals of adults give
the bell a lacy appearance. The oral arms are generally straight, and the planulae
are found in variable colors. The bells are peach or whitish, male gonads are dark
purple, and female gonads pale brown. Northern moon jellies range in size from 14-29
cm.
- Other Physical Features
- ectothermic
- heterothermic
- radial symmetry
- venomous
- Sexual Dimorphism
- sexes alike
- sexes colored or patterned differently
Development
Male and female medusa spawn into the sea where the eggs are fertilized. The fertilized egg is called a planula, a cilliated organism that is elliptical and elongated. The planulae are brooded on the manubrium of Aurelia labiata . They are shaken off and attach to a substrate, usually hanging upside-down from the underside of docks, mussel shells, or rocks. There they transform into a polyp 2-3 mm in height, with an oral disk 1-2 mm in diameter. Polyps range in color from whitish to pale pink and orange. Polyps attached to a substrate asexually reproduce by side budding, stolon budding, or podocyst formation.
Eventually the polyp strobilates, meaning that it transforms into a stack of several
organisms. In moon jellies, the strobila are both monodisk (produced one at a time)
and polydisk (several disks produced), with more than 20 developing ephyrae (free-swimming,
immature medusae). Their color varies with location (cinnamon in Southern California
and tan in Monterey). The strobilation time lasts for about 7 days, and the ephyrae
are released. Typical ephyrae are 2-3 mm when released, with 8 marginal arms and nematocysts
(stinging cells) on the exumbrellar surface. The ephyrae swim about until they develop
into mature medusa form.
- Development - Life Cycle
- metamorphosis
Reproduction
Moon jellies reproduce using internal fertilization. The gonads are one of the most
recognizable characteristics of the animal. They are horseshoe shaped organs with
deep coloration that can be seen in the center of the bell. In the mating season,
males are seen with sperm filaments attached to their oral arms. Sperm is carried
to the gastric pouch of the female by cilliary currents. Females hold the fertilized
eggs, which appear as grey clumps, on the manubrium.
Only recently has
Aurelia labiata
been redefined as a species unique to its close relative
Aurelia aurita
, the saucer jelly. Information on reproductive behavior or
A. labiata
is not available at this time.
Aurelia aurita
is known to reach sexual maturity in the spring and summer. In these seasons much
of the organism's energy is devoted to repoduction. As the jellies live in close
aggregations, complex mating rituals do not exist, males simply release their sperm
filaments during the period of sexual maturity, which are carried to the female gonads
by ciliary currents.
- Key Reproductive Features
- seasonal breeding
- sexual
- fertilization
The zygotes of
Aurelia labiata
, called planulae, are brooded on the jelly's manubrium. In the Southern form, this
takes place in a reticulating pattern on the frills. In the central form, the planulae
are brooded in tear-drop shape clumps on the base or shelves of the manubrium. Northernmost
moon jellies brood planulae at the base or shelves of the manubrium as well. Planulae
are eventually shaken off and continue their development after attaching to a substrate.
- Parental Investment
- no parental involvement
-
pre-fertilization
- provisioning
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
Lifespan/Longevity
Aurelia labiata
polyps usually strobilate early in spring, and the medusae mature very quickly, spawn,
and die by midsummer or early fall. In certain places, the medusae population is present
year-round.
Behavior
Moon jellies appear in aggregations of hundreds to millions of individuals. These
aggregations are widely studied in Prince William Sound, Alaska, suggesting that the
jellies get stuck in flow features of the water column, forming the groups. Reduced
swimming due to collisions amongst the medusae in crowded areas is believed to assist
in maintenance of the aggregations. Possible advantages of aggregating behavior includes
increased fertilization success, the ability to stay near shore where zooplankton
and planula settling sites are more abundant, and reduced predation.
- Key Behaviors
- natatorial
- sessile
- motile
- colonial
Communication and Perception
Little is known about communication between moon jellies. They are relatively primitive animals, so it is likely that if communication between individuals exists at all, it is in a very simple form. Research in this area is lacking.
Food Habits
Aurelia labiata feeds on small zooplankton such as molluscs, crustaceans, fish eggs, and other small jellies. In a gut sampling study, moon jellies primarily selected for crustacean prey. Thorough research on the specific dietary habits is missing from scientific discourse, but the close relative species Aurelia aurita has a diet of plankton organisms as well. Aurelia aurita has a diet dominated by whatever prey type is abundant, adjusting to the availability of given food types.
The plankton is caught on the mucus lining the bell of the jelly. It is moved by ciliary
action to the bell margin, where the short fringe of tentacles helps funnel the food
into the manubrium and the four horseshoe-shaped stomach pouches at the top center
of the bell.
- Primary Diet
-
carnivore
- eats non-insect arthropods
- planktivore
- Animal Foods
- eggs
- mollusks
- aquatic crustaceans
- cnidarians
- zooplankton
- Plant Foods
- phytoplankton
Predation
The moon jelly has stinging cells called nematocysts with which it can sting potential
predators. The sting is mild and does not harm humans.
Birds, turtles, and
Cyanea capillata
are cited as predators of moon jellies.
Ecosystem Roles
Aurelia labiata
is an important consumer of marine zooplankton. They overlap spacially and temporally
with important commercial fish, such as the
walleye pollock
in the Prince William Sound. They potentially compete with these fish species, which
also feed on marine zooplankton. Studies have yet to prove that large jellyfish,
especially
A. labiata
, significantly threaten the livelihood of zooplanktivorous fish, but they have shown
that their diets and habitats overlap. This could lead to competition for resources.
Economic Importance for Humans: Positive
Aurelia labiata
adapt readily to an aquarium environment and can thrive at a variety of temperatures.
In addition, their translucent coloring, moon-shaped bell, and pulsating method of
swim make them very beautiful. It is relatively easy to establish polyps and breed
the jellies in captivity. For these reasons, moon jellies are some of the most displayed
jellyfish at public aquariums. Distributors of jellyfish have opened a new market
among consumers who want moon jelly tanks in their homes.
Aurelia labiata
is emerging as an important commodity in the pet trade, and serves as an attraction
at aquariums worldwide.
- Positive Impacts
- pet trade
Economic Importance for Humans: Negative
There is concern, but no causal evidence as of yet, that the blooming populations
of moon jellies will dominate consumption of zooplankton food resources and outcompete
commercial fish that also depend on the resource. Further studies will be necessary
to determine if this concern is valid.
Conservation Status
Moon jellies exist in large numbers, with stable populations year round.
Other Comments
In classifying different species of jellyfish, twentieth century taxonomists tended
to classify any flat, whitish medusa with four horseshoe-shaped gonads as
Aurelia aurita
. Many morphological differences have thus been ignored, and false conclusions about
species such as
Aurelia labiata
have been made. Rigorous research by Lisa-Ann Gershwin on the anatomical species
has resurrected
Aurelia labiata
as a species unique from its close relatives. For decades the individuality of the
species was ignored.
Additional Links
Contributors
Renee Sherman Mulcrone (editor).
Chelsea MacMullan (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.
- Nearctic
-
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
- temperate
-
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
- saltwater or marine
-
mainly lives in oceans, seas, or other bodies of salt water.
- pelagic
-
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- heterothermic
-
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
- radial symmetry
-
a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).
- venomous
-
an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).
- metamorphosis
-
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- internal fertilization
-
fertilization takes place within the female's body
- natatorial
-
specialized for swimming
- sessile
-
non-motile; permanently attached at the base.
Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa
- motile
-
having the capacity to move from one place to another.
- colonial
-
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
- zooplankton
-
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
- phytoplankton
-
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
- pet trade
-
the business of buying and selling animals for people to keep in their homes as pets.
- carnivore
-
an animal that mainly eats meat
- planktivore
-
an animal that mainly eats plankton
References
Gershwin, L. 2001. Systematics and Biogeography of the jellyfish Aurelia labiata (Cnidaria:Scyphozoa). The Biological Bulletin , 201/1: 104-119.
Hickman, C., L. Roberts, A. Larson. 2003. Animal Diversity . Boston: McGraw Hill.
Monterey Bay Aquarium Foundation, 2003. "Moon Jelly: Aurelia labiata" (On-line). Monterey Bay Aquarium. Accessed December 20, 2004 at http://www.mbayaq.org/efc/living_species/print.asp?inhab=442 .
Purcell, J., K. Stokesbury, E. Brown, L. Haldorson, T. Shirley. 2000. Aggregations of the jellyfish Aurelia labiata: abundance, distribution, association with age-0 walleye pollock, and behaviors promoting aggregation in Prince William Sound, Alaska, USA. Marine Ecology Progress Series , 195: 145-158. Accessed December 20, 2004 at http://www.int-res.com/abstracts/meps/v195/p145-158.html .
Purcell, J., M. Sturdevant. 2001. Prey Selection and dietary overlap among zooplanktivorous jellyfish and juvenile fishes in Prince William Sound, Alaska. Marine Ecology Progress Series , 210: 67-83.
Purcell, J. 2002. "Predation on Zooplankton by jellyfish and the Potential for Competition for Food with Commercial Fishes" (On-line ). Accessed 03/20/03 at http://aslo.org/meetings/victoria2002/archive/403.html .
Robel, D. 2001. "Aurelia labiata:Moon Jelly" (On-line). Jellies Zone. Accessed December 20, 2004 at http://jellieszone.com/aurelia.htm .
Rodriguez, R. 1996. "Aurelia aurita" (On-line). Animal Diversity Web. Accessed December 20, 2004 at http://animaldiversity.ummz.umich.edu/accounts/aurelia/a._aurita$narrative.html .