''Chrysaora hysoscella'', the compass jellyfish, is a common species of

jellyfish Jellyfish, also known as sea jellies or simply jellies, are the #Life cycle, medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animal ...

that inhabits coastal waters in temperate regions of the northeastern Atlantic Ocean, including the

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

and

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

. 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 In taxonomy, an undescribed taxon is a taxon (for example, a species) that has been discovered, but not yet formally described and named. The various Nomenclature Codes specify the requirements for a new taxon to be validly described and named. U ...

tentatively referred to as "''C. agulhensis''". It is a true jellyfish displaying

radial symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symme ...

with distinct brown markings shaped like elongated V's on its bell. ''C. hysoscella'' adults are highly susceptible to the parasite

Hyperia medusarum ''Hyperia'' is a genus of amphipods in the family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis ...

, but this has had no significant effects on the population. This organism has a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

polyp stage before developing into a

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

adult

medusae Jellyfish, also known as sea jellies or simply jellies, are the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals, althoug ...

. Compass jellyfish consume a variety of

marine invertebrates Marine invertebrates are invertebrate animals that live in marine habitats, and make up most of the macroscopic life in the oceans. It is a polyphyletic blanket term that contains all marine animals except the marine vertebrates, including the ...

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.

Body plan

As an adult, the bell of the compass jellyfish typically has a diameter of . 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. Juveniles on the other hand lack the compass pattern, they apper white and polka dotted with a reddish fringe on the edge of their bell. 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. 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. It has 4 oral arms that can be distinguished from the tentacles because the arms are noticeably longer and have a folded, frilly appearance. 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.

Habitat

The compass jellyfish is found in coastal waters of the northeast Atlantic, including the

Celtic Celtic, Celtics or Keltic may refer to: Language and ethnicity *pertaining to Celts, a collection of Indo-European peoples in Europe and Anatolia **Celts (modern) *Celtic languages **Proto-Celtic language *Celtic music *Celtic nations Sports Foot ...

, Irish,

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology T ...

and

Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

Seas. They inhabit these waters mostly at the top of the water column, 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. They are rarely found deeper than 30 m from the surface.

Feeding and predation

Compass jellyfish are

carnivores A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...

, consuming other marine invertebrates and plankton. They feed on a variety of

and

organisms including but not limited to:

dinoflagellates The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

copepods Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (living in the water column), some are benthic (living on the sediments), several species have ...

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

eggs, larval fish, and

chaetognaths The Chaetognatha or chaetognaths (meaning ''bristle-jaws'') are a phylum of predatory marine worms that are a major component of plankton worldwide. Commonly known as arrow worms, they are mostly pelagic; however about 20% of the known species ...

. They stun and capture their prey with stinging cells on their tentacles. The oral arms facilitate movement of captured prey into the oral opening. Compass jellyfish have very few predators. They are known to be consumed by the leatherback sea turtle and

ocean sunfish The ocean sunfish (''Mola mola''), also known as the common mola, is one of the largest bony fish in the world. It is the type species of the genus ''Mola'', and one of five extant species in the family Molidae. It was once misidentified as th ...

.Jones, Georgina. ''A field guide to the marine animals of the Cape Peninsula.'' SURG, Cape Town, 2008.

Life cycle

Like other Scyphozoans, ''Chrysaora hysoscella'' undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

as the organism develops and experiences a polyp and then

medusa In Greek mythology, Medusa (; ), also called Gorgo () or the Gorgon, was one of the three Gorgons. Medusa is generally described as a woman with living snakes in place of hair; her appearance was so hideous that anyone who looked upon her wa ...

form. Females release planular larvae which swim to find a suitable place to settle. The planulae attach to a

substrate and develop into a sessile polyp which releases immature medusae through

asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the f ...

called

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. This mode of reproduction is characterized by high offspri ...

. ''Chrysaora hysoscella'' function as a male upon maturity and then develop female gametes, meaning this organism is protandrously hermaphroditic.

Reproduction

''Chrysaora hysoscella'' utilize both sexual and

throughout development. Mature individuals reproduce sexually by

broadcast spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...

. Males release sperm from their mouths into the water column. Females fertilize the sperm internally and can fertilize sperm from multiple male partners. The larvae released from the female settle as

polyps A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral (opposite to oral) en ...

that reproduce asexually. The polyps release multiple ephyrae through

. Ephyrae are the earliest form of the medusa stage. Research indicates that ''Chrysaora hysoscella''

are capable of releasing ephyrae over time and therefore are not limited to a single reproductive event.

Parasite ''Hyperia medusarum''

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 A body cavity is any space or compartment, or potential space, in an animal body. Cavities accommodate organs and other structures; cavities as potential spaces contain fluid. The two largest human body cavities are the ventral body cavity, a ...

in the umbrella and

gonads A gonad, sex gland, or reproductive gland is a mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, ...

but tends to move from umbrella to

if there is space for them there. The

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.

Effects of global warming

Scyphozoa The Scyphozoa are an exclusively marine class of the phylum Cnidaria, referred to as the true jellyfish (or "true jellies"). The class name Scyphozoa comes from the Greek word '' skyphos'' (), denoting a kind of drinking cup and alluding to the ...

populations are increasing with the warming climate and warmer ocean temperatures. Studies suggest that warmer winter temperatures allow for a longer

period and subsequently higher ephyra production per polyp, higher percentages of polyp

, and higher polyp survival rate.

Polyps A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral (opposite to oral) en ...

will be more successful in warmer temperatures but not in extreme temperatures. ''C. hysoscella'' are predicted to migrate further northwards to maintain ideal conditions.

Impact

Thriving jellyfish populations have been found to take over as top predators in areas where fin fish have been over-exploited. Increased abundance of jellyfish negatively impacts fish populations in the same region because jellyfish feed on fish eggs and larvae. 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. 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.

References

External links

* {{Taxonbar, from=Q2440379 hysoscella Articles containing video clips Animals described in 1766 Taxa named by Carl Linnaeus