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.
Known Predators:
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.
Range mass: 0.2 to 2.4 kg.
Range length: 3 to 43 (diameter) cm.
Average length: 15.31 cm.
Other Physical Features: ectothermic ; heterothermic ; radial symmetry ; venomous
Sexual Dimorphism: female larger
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.
Average lifespan
Status: wild: 1 years.
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.
Range depth: 30 to 2 m.
Habitat Regions: temperate ; saltwater or marine
Aquatic Biomes: pelagic ; coastal
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 (Native ); ethiopian (Native ); atlantic ocean (Native )
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.
Animal Foods: aquatic crustaceans; other marine invertebrates; zooplankton
Primary Diet: carnivore (Eats non-insect arthropods); planktivore
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
Perception Channels: visual ; chemical
This species does not currently have any special conservation status.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
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
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 )
There are currently no known positive economic effects of compass jellyfish on humans.
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.
Commensal/Parasitic Species:
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)
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.
Breeding interval: This species experiences a single sexual breeding season yearly, but can also reproduce asexually until reaching adulthood.
Breeding season: Generally over the course of a season (3-4 months), either winter or summer depending on the location of the species.
Key Reproductive Features: semelparous ; iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sequential hermaphrodite (Protandrous ); sexual ; asexual ; fertilization (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 ; pre-hatching/birth (Protecting: Female)
Chrysaora hysoscella, the compass jellyfish,[1] is a common species of jellyfish that inhabits coastal waters in temperate regions of the northeastern Atlantic Ocean, including the North Sea and Mediterranean Sea.[2] In the past it was also recorded in the southeastern Atlantic, including South Africa, but this was caused by confusion with close relatives; C. africana, C. fulgida and an undescribed species tentatively referred to as "C. agulhensis".[2][3][4][5]
It is a true jellyfish displaying radial symmetry with distinct brown markings shaped like elongated V's on its bell.[6] C. hysoscella adults are highly susceptible to the parasite hyperia medusarum, but this has had no significant effects on the population.[7] This organism has a benthic polyp stage before developing into a pelagic adult medusae.[6] Compass jellyfish consume a variety of marine invertebrates and plankton and are preyed on by very few.[8] C. hysoscella contribute to the global issue of jellyfish overpopulation which is concerning to humans for various reasons including recreational interference, economic turmoil for fishing communities, and depleted fish resources.[9]
As an adult, the bell of the compass jellyfish typically has a diameter of 15–25 cm (5.9–9.8 in).[2] It usually has 16 brown elongated V-shaped markings on the translucent yellow-white bell. The markings surround a central brown spot and resemble the face of a compass, hence the common name compass jellyfish.[6] It is usually colored yellowish white, with some brown. Its 24 tentacles are arranged in eight groups of three. Each tentacle has stinging cells for capturing prey and defense from predators.[10] A sense organ is located between each group of tentacles, which can perceive changes in light and helps the jellyfish determine and maintain its position in the water column.[6] It has 4 oral arms that can be distinguished from the tentacles because the arms are noticeably longer and have a folded, frilly appearance.[10] These arms are used to facilitate transfer of captured prey from the tentacles to the mouth which is between the oral arms at the center of the underside of the bell.[10]
The compass jellyfish is found in coastal waters of the northeast Atlantic, including the Celtic, Irish, North and Mediterranean Seas.[2][11] They inhabit these waters mostly at the top of the water column,[12][13] and although they inhabit shallow water, they move up and down in the water column often ranging from surface waters to just above the seabed.[12] They are rarely found deeper than 30 m from the surface.[12][7]
Compass jellyfish are carnivores, consuming other marine invertebrates and plankton.[8] They feed on a variety of benthic and pelagic organisms including but not limited to: dinoflagellates, copepods, crustacean eggs, larval fish, and chaetognaths.[8] They stun and capture their prey with stinging cells on their tentacles.[6] The oral arms facilitate movement of captured prey into the oral opening.[10] Compass jellyfish have very few predators. They are known to be consumed by the leatherback sea turtle and ocean sunfish.[14]
Like other Scyphozoans, Chrysaora hysoscella undergo metamorphosis as the organism develops and experiences a polyp and then medusa form. Females release planular larvae which swim to find a suitable place to settle. The planulae attach to a benthic substrate and develop into a sessile polyp which releases immature medusae through asexual reproduction called strobilation.[15][16] Chrysaora hysoscella function as a male upon maturity and then develop female gametes, meaning this organism is protandrously hermaphroditic.[17][16]
Chrysaora hysoscella utilize both sexual and asexual reproduction throughout development.[17] Mature individuals reproduce sexually by broadcast spawning. Males release sperm from their mouths into the water column.[6] Females fertilize the sperm internally and can fertilize sperm from multiple male partners.[17] The larvae released from the female settle as benthic polyps that reproduce asexually.[16] The polyps release multiple ephyrae through strobilation.[15] Ephyrae are the earliest form of the medusa stage. Research indicates that Chrysaora hysoscella polyps are capable of releasing ephyrae over time and therefore are not limited to a single reproductive event.[16][15]
Adult Chrysaora hysoscella are often parasitised by Hyperia medusarum. C. hysoscella found inshore and closer to the surface are more likely to have the parasite. The parasite can be found inside of the body cavity in the umbrella and gonads but tends to move from umbrella to gonads if there is space for them there. The gonads are more enriched in carbon and protein content then any other part of the body, making this region the ideal location to settle and feed. They have also been found on the oral arms of the jellyfish where they can eat prey caught by the medusae.[7]
Scyphozoa populations are increasing with the warming climate and warmer ocean temperatures. Studies suggest that warmer winter temperatures allow for a longer strobilation period and subsequently higher ephyra production per polyp, higher percentages of polyp strobilation, and higher polyp survival rate. Polyps will be more successful in warmer temperatures but not in extreme temperatures. C. hysoscella are predicted to migrate further northwards to maintain ideal conditions.[15]
Thriving jellyfish populations have been found to take over as top predators in areas that fin fish have been over-exploited.[8] Increased abundance of jellyfish negatively impacts fish populations in the same region because jellyfish feed on fish eggs and larvae.[13] Jellyfish and larval fish can also share common dietary preferences. Competition for food resources can result in depleted fish populations. Overpopulation of jellyfish is a concern to humans for many reasons.[9] Jellyfish stings are painful and sometimes deadly to humans. Fishing nets can be overwhelmed with jellyfish bycatch or torn by jellyfish caught in the nets. Jellyfish can clog water inlets to power plants, causing serious problems for power production. Jellyfish can invade aquaculture cages, ruining the production of the organism being farmed.[9]
Chrysaora hysoscella, the compass jellyfish, is a common species of jellyfish that inhabits coastal waters in temperate regions of the northeastern Atlantic Ocean, including the North Sea and Mediterranean Sea. In the past it was also recorded in the southeastern Atlantic, including South Africa, but this was caused by confusion with close relatives; C. africana, C. fulgida and an undescribed species tentatively referred to as "C. agulhensis".
It is a true jellyfish displaying radial symmetry with distinct brown markings shaped like elongated V's on its bell. C. hysoscella adults are highly susceptible to the parasite hyperia medusarum, but this has had no significant effects on the population. This organism has a benthic polyp stage before developing into a pelagic adult medusae. Compass jellyfish consume a variety of marine invertebrates and plankton and are preyed on by very few. C. hysoscella contribute to the global issue of jellyfish overpopulation which is concerning to humans for various reasons including recreational interference, economic turmoil for fishing communities, and depleted fish resources.
