Chrysaora hysoscella

Geographic Range

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.

• Biogeographic Regions
• palearctic palearctic
  • native native
• ethiopian ethiopian
  • native native
• atlantic ocean atlantic ocean
  • native native

Habitat

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.

• Habitat Regions
• temperate temperate
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic
• coastal coastal

Physical Description

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.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• radial symmetry radial symmetry
• venomous venomous

• Sexual Dimorphism
• female larger

Development

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.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

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.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

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.

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.

• Key Reproductive Features
• semelparous semelparous
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sequential hermaphrodite
  • protandrous protandrous
• sexual sexual
• asexual asexual
• fertilization fertilization
  • internal internal
• broadcast (group) spawning

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.

• Parental Investment
• no parental involvement
• female parental care female parental care
• pre-hatching/birth
  • protecting
    • female

Lifespan/Longevity

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.

Behavior

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.

• Key Behaviors
• natatorial natatorial
• sessile sessile
• motile motile
• solitary solitary

Home Range

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.

Communication and Perception

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.

• Communication Channels
• chemical chemical

• Perception Channels
• visual visual
• chemical chemical

Food Habits

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.

• Primary Diet
• carnivore carnivore
  • eats non-insect arthropods
• planktivore planktivore

• Animal Foods
• aquatic crustaceans
• other marine invertebrates
• zooplankton zooplankton

Predation

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.

Ecosystem Roles

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.

Economic Importance for Humans: Positive

There are currently no known positive economic effects of compass jellyfish on humans.

Economic Importance for Humans: Negative

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.

• Negative Impacts
• injures humans
  • bites or stings
  • venomous venomous

Conservation Status

This species does not currently have any special conservation status.

Additional Links

Encyclopedia of Life

Contributors

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.

References

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