Compass jellyfish are found in coastal areas of the northeast Atlantic Ocean, particularly in the Celtic, Irish, and North Seas (greatest abundance between 50.0°–52.0° N). They are also found in the Mediterranean Sea and coastal regions of South Africa. (Doyle, et al., 2007; Hays, et al., 2008; Mariottini and Pane, 2010)
Compass jellyfish are marine organisms that live in cold or temperate waters (between 4°C and 28°C) relatively near the coast in continental shelf regions. Adults can usually be observed near the surface of the water, but when currents near the surface become too rough, they are known to dive deeper in the water column (down to 26.9 m) and can be found just half a meter from the seabed. Overall, it is uncommon for this species to be found below 30m. (Buecher, et al., 2001; Doyle, et al., 2007; Fish and Fish, 1989; Hays, et al., 2008; Houghton, et al., 2007; Mariottini and Pane, 2010)
As adults, compass jellyfish have a typical medusa body plan and display radial symmetry around the oral-aboral axis. The size of the flattened, saucer-shaped bell, which plays an important role in swimming, ranges from 3 cm to 43 cm with a median diameter of 15.31 cm, and can weigh anywhere from 0.2-2.4 kg. The aboral surface of the bell can be various shades of brown and has V-shaped markings around a central spot. These jellyfish have extendable and retractable tentacles that are arranged in eight groups of three (a total of 24 tentacles). The tentacles have stinging cells to capture prey, and a sense organ, which can detect light and olfactory stimuli, is located between each group of tentacles. Additionally, there are four arms, longer than the diameter of the organism, that surround the mouth. This species changes from male to female over the course of its lifespan, meaning that the female stage is larger than the male stage, on average. (Fish and Fish, 1989; Hays, et al., 2008; Houghton, et al., 2007)
Compass jellyfish are scyphozoans and exhibit a life cycle characteristic to other organisms in this class. Planulae are released from the female and swim freely for a few days before settling on a substrate (preferably abiotic) and becoming a benthic polyp (scyphistoma). The scyphistoma reproduces asexually (strobilation) by releasing multiple ephyrae (an immature medusa stage) typically between the spring and autumn. Research has shown that there is equal representation of different levels of maturity among the medusa stage at any given time, indicating that many ephyrae are released over a period of time, as opposed to many at once. The maturation of the ephyra stage to the adult form can take a week to months and typically occurs between the spring and summer. There is evidence to suggest that the early ephyra stage can experience reverse development and transform back into a polyp, rather than maturing into an adult. However, once in the adult stage, reverse development is not possible and an individual is likely to undergo sexual reproduction. Because this species is a protandrous hermaphrodite, upon maturity, an individual will initially function as a male, later transitioning to the production of female gametes. ("Compass jellyfish: Chrysaora hysoscella", 2003; Calder, 1982; De Vito, et al., 2006; Fish and Fish, 1989; Holst and Jarms, 2007; Holst and Jarms, 2010; Houghton, et al., 2007)
Specific information regarding the mating systems of this species is currently unavailable, including how mates are found or triggers for gamete relaease. As broadcast spawners, males and females potentially have many mates. (Fish and Fish, 1989; Houghton, et al., 2007)
This species can reproduce sexually or asexually. Release of ephyrae by strobilating scyphostoma is a form of asexual reproduction, whereas mature medusae are capable of sexual reproduction. The time for an ephyra to mature into a sexually mature adult (male) is up to a few months (typically between spring and summer in northern regions). There is variation in the sizes of the medusae (representing different stages of maturity) present in the population at a given time, but research has shown that there are more large individuals during seasons in which sexual reproduction occurs. These seasons vary with location; for example, in the North Sea, large medusae are numerous in the summer and autumn, whereas they are numerous in the winter near South Africa. Temperature and food supply could play a role in causing this difference, although further research is needed to assess these claims. (Buecher, et al., 2001; Fish and Fish, 1989; Houghton, et al., 2007)
Sperm are released from the mouth of a functional male and taken in by the mouth of a female; fertilization is internal. After fertilization, free-swimming planula larvae are released by the female and settle as polyps a few days later. From the polyp form, research has shown that this species does not exhibit a single, synchronized reproductive cohort, instead releasing ephyrae over a several month period. (Fish and Fish, 1989; Houghton, et al., 2007)
Males have no parental investment in their offspring. Females offer some protection to their developing young by sheltering them inside their bells until the free-swimming planula stage is ready to be released. (Fish and Fish, 1989; Houghton, et al., 2007)
The lifespan of compass jellyfish is about one year. Between the months of June and August, it is estimated that 95% of the total medusae experience a brief stranding period, where they wash up on the shore and die. The reason for this phenomenon is unknown, but based on current research, it has been hypothesized that mature medusae die after gamete release, which then causes them to strand. Evidence to support this hypothesis comes from previous studies performed on related species, and observations that recently stranded mature compass jellyfish are without oral arms or peripheral tentacles, which suggests that they died before washing ashore. It has also been found that some small, sexually immature medusae may strand due to the inability to withstand strong currents. (Fish and Fish, 1989; Houghton, et al., 2007)
Compass jellyfish swim using movements of their bell to pump water and propel them forward. Individuals are solitary and generally remain near the surface of marine waters in coastal pelagic regions, although they have been documented to make extensive vertical movements through the water column over periods of several hours. (Doyle, et al., 2007; Hays, et al., 2008; Holst and Jarms, 2010)
Although they have some level of control over their position in the water column, compass jellyfish are largely carried on ocean currents and thus, do not maintain well-defined home ranges or territories. (Hays, et al., 2008)
Compass jellyfish are able to perceive their orientation and maintain positional equilibrium via sensory cells called statocysts that are found within larger sensory structures called rhopalia. The rhopalia also contain pigmented spots that help the jellyfish to perceive changes in light, as well as sensory pits that can detect chemical cues in the water. It is likely that chemicals are the main means by which these jellyfish would communicate, but as they are largely solitary animals, their communication has yet to be thoroughly studied. (Arai, 1997; Doyle, et al., 2007; Wrobel, 2004)
This species feeds on other marine invertebrates, such as phyllopods (Penilia avirostris), copepods (Acartia and Centropages sp.), and decapod larvae. They are also known to feed on plankton. Compass jellyfish use their four oral tentacles to move food towards the mouth. The tentacles bear nematocysts or stinging cells that subdue the prey, aiding in their capture and preventing damage to the jellyfishes' delicate tentacles. ("Britannica Online Encylopedia", 2012; Barz and Hirche, 2007; Den Hartog and Van Nierop, 1984)
Compass jellyfish can be consumed by predators such as leatherback sea turtles and ocean sunfish. Studies have shown that individuals allow themselves to drift into deeper waters when they feel threatened by potential predators, or to avoid rough waves. (Arai, 1997; Hays, et al., 2008; Houghton, et al., 2006)
This species is a potentially important prey item to the predators indicated above, as well as serving as a predator of many different types of marine crustaceans. These prey items are also fed on by many species of fish, resulting in competition between jellyfish and these other predatory species. Additionally, compass jellyfish play host to at least two species of parasitic amphipods, which feed on the jellyfishes' gonads. (Buecher, et al., 2001; Dittrich, 1988; Purcell, et al., 2007)
There are currently no known positive economic effects of compass jellyfish on humans.
Climate change and competition for prey between fish species and compass jellyfish has resulted in a large increase in the jellyfish population, while causing a decline in the number of fish within the last twenty years. The dominance switch from fish to jellyfish has a negative impact on the fishing industry. Jellyfish can also spoil fish catches by bursting trawl nets. Furthermore, this species has been known to interfere with power generation by obstructing intakes, hinder diamond mining by blocking sediment suction, and sting humans on occasion, causing wounds that, while painful, are rarely severe. (Hays, et al., 2008; Lynam, et al., 2006; Purcell, et al., 2007)
This species does not currently have any special conservation status. (IUCN, 2012)
Kailyn Dawson (author), The College of New Jersey, Cara Giordano (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Jeremy Wright (editor), University of Michigan-Ann Arbor.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
parental care is carried out by females
union of egg and spermatozoan
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.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
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.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats plankton
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products
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).
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.
non-motile; permanently attached at the base.
Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa
reproduction that includes combining the genetic contribution of two individuals, a male and a female
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).
an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).
uses sight to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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