100px x 1020px Jellyfish75px x 1020px About Terminology Anatomy

Classification &

EvolutionLifecycle Ecology Relationship

to Human Taxonomy Haeckel’sMedusae

Pic of Jelly Fish

Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jelly-fish have roamed the seas for at least 500 mil-lion years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal.

About The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclu-sively to the non-polyp life-stage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing ten-tacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example cteno-phores (members from another phylum of common, gelatinous and generally transparent or translucent, free-swimming planktonic carni-vores now known as comb jellies) were included as "jellyfishes".[4] Even some scientists include the phylum ctenophora when they are referring to jellyfish.[5] Other scientists prefer to use the more all-encompassing term gelatinous zoo-plankton, when referring to these, together with other soft-bodied animals in the water column.[6] As jellyfish are not vertebrates, let alone true fish, the word jellyfish is considered by some to be a misnomer. Public aquariums may use the terms jellies or sea jellies instead.[7] Some sources may use the term "jelly" to refer to organisms in this taxon, as "jellyfish" may be considered inappropriate.[8]Many textbooks and sources refer to only scy-phozoa as "true jellyfish".[9][10]A group of jellyfish is sometimes called a bloom or a swarm.[11] "Bloom" is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, refer-ring to seasonal increases, or numbers beyond what was expected.[12] Another collective name for a group of jellyfish is a smack,[13] although this term is not commonly used by scientists who study jellyfish. Jellyfish are "bloomy" by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large numbers, even when an ecosystem is in balance.[14] Using "swarm" usually implies some kind of active ability to stay together, which a few species such as Aurelia, the moon jelly, demonstrate.[15]Medusa jellyfish may be classified as scyphome-dusae ("true" jellyfish), stauromedusae (stalked jellyfish), cubomedusae (box jellyfish), or hydro-medusae, according to which clade their species belongs.[16]In biology, a medusa (plural: medusae) is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below. The upper or aboral surface is called the exumbrella and the lower surface is called the subumbrella; the mouth is located on the lower surface, which may be partially closed by a membrane extending inward from the margin (called the velum). The digestive cavity consists of the gastrovascular cavity and radiating canals which extend toward the margin; these canals may be simple or branching, and vary in number from few to many. The margin of the disk bears

Terminology

Most jellyfish do not have specialized digestive, osmoregulatory, central nervous, respi-ratory, or circulatory systems. The manubrium is a stalk-like structure hanging down from the centre of the underside, with the mouth at its tip. This opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. It is joined to the radial canals which extend to the margin of the bell.[17] Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement, but can use their hydrostatic skeleton to navigate through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are mostly passive.[citation needed] The body is composed of over 95% water; most of the umbrella mass is a gelatinous material — the jelly — called mesoglea which is surrounded by two layers of protective skin. The top layer is called the epidermis, and the inner layer is referred to as gastrodermis, which lines the gut.

Anatomy

Medusa jellyfish are a life stage exhibited in some species of the phylum Cnidaria. Medusa jellyfish belong exclusively to Medusozoa, the clade of cnidarians which excludes Anthozoa (e.g., corals and anemones). This suggests that the medusa form evolved after the polyps.[32]The phylogenetics of this group are complex and still being worked out. The Medusozoa appear to be a sister group to Octocorallia.[33] Staurozoa appears to be the earliest diverging; Cubozoa and the coronate Scyphozoa form a clade that is the sister group of Hydrozoa plus discomedusan Scyphozoa. The Hydrozoa are the sister group of discomedusan Scyphozoa. Limnomedusae (Trachylina) is the sister group of hydroido-linans. This group may be the earliest diverging lineage among Hydrozoa. Semaeostomeae is a paraphyletic clade with Rhizostomeae. There are four major classes of meduso-zoan Cnidaria:Scyphozoa are often called true jellyfish. They have tetra-radial symmetry. They have tentacles around the outer margin of the bowl-shaped bell, and oral arms around the mouth.Cubozoa (box jellyfish) have a box-shaped bell, and their velarium assists them to swim more quickly. Box jellyfish may be related more closely to "true jellyfish" than either are to hydrozoa.[32]Hydrozoa may form medusa which resemble scyphozoans (but generally with a velum) and are distinguished by an absence of cells in the mesoglea. However, many hydrozoa species do not form medusa at all (such as hydra, which is hence not considered a jellyfish).Staurozoa (stalked jellyfish) do not have a polyp stage, however the medusa is generally sessile, oriented upside down and with a stalk from the "bell" planted to the substrate. Until recently, staurozoa was classified within scyphozoa.Some other animals are frequently associated with or mistaken for medusa jellyfish.Siphonophorae are an order of hydrozoa which generally live as colonies (for example, free-swimming chains of repeated units, some units similar to polyps or to medusa). They are not considered medusa jellyfish. A well-known example is the Portuguese Man o' War.Ctenophores (comb jellies) are a separate phylum from cnideria. Their method of propolsion is cillia paddles rather than a pulsating bell.Salps are transparent, gelatinous marine organ-isms that form pelagic colonies like siphono-phores. Salps are chordates, and as such are actually more closely related to humans than

Classification & Evolution

Most jellyfish alternate between polyp and medusa generations during their life cycle. Addi-tionally, there are several possible larval life-stages. After fertilization a primitive free-swimming larval form, called the planula, devel-ops. The planula is a small larva covered with cilia. It settles onto a firm surface and develops into a polyp. Some polyps can also asexually produce a creeping frustule larval form, which then also develops into a new polyp.The polyp is generally a small planted stalk with a mouth that is ringed by upward-facing ten-tacles. The polyps are like miniatures of the closely related anthozoan (sea anemones and corals) polyps, which are also members of Cni-daria. The jellyfish polyp may be sessile, living on the bottom or another substrate such as floats or boat hulls, or it may be free-floating or attached to tiny bits of free-living plankton[37] or rarely, fish[38] or other invertebrates. Polyps may be solitary or colonial. Polyp colonies form by strobilation, resulting in multiple polyps which share a common stomach cavity.[39] Most polyps are very small, measured in millimeters. They feed continuously. The polyp stage may last for years.Eventually the polyp gives rise to the medusa stage. New medusae are usually created asexu-ally by strobilation or budding from the polyp. The medusa is the life stage which is most typi-cally identified as a jellyfish.

Lifecycle

100px x 1020px Jellyfish75px x 1020px About Terminology Anatomy

Classification &

EvolutionLifecycle Ecology Relationship

to Human Taxonomy Haeckel’sMedusae

Pic of Jelly Fish

Jellyfish or jellies are the major non-polyp form of individu-als of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while sting-ing tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwa-ter. Large, often colorful, jellyfish are common in coastal zones world-wide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal.

About

The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp life-stage which occurs in many cnidar-ians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals shar-ing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transpar-ent or translucent, free-swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes".[4] Even some scien-tists include the phylum ctenophora when they are referring to jellyfish.[5] Other scientists prefer to use the more all-encompassing term gelatinous zooplankton, when referring to these, together with other soft-bodied animals in the water column.[6] As jellyfish are not verte-brates, let alone true fish, the word jellyfish is considered by some to be a misnomer. Public aquariums may use the terms jellies or sea jellies instead.[7] Some sources may use the term "jelly" to refer to organ-isms in this taxon, as "jellyfish" may be considered inappropriate.[8]Many textbooks and sources refer to only scyphozoa as "true jellyfish".[9][10]A group of jellyfish is sometimes called a bloom or a swarm.[11] "Bloom" is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, referring to sea-sonal increases, or numbers beyond what was expected.[12] Another collective name for a group of jelly-fish is a smack,[13] although this term is not commonly used by scientists who study jellyfish. Jelly-fish are "bloomy" by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large num-

Terminology

Most jellyfish do not have specialized digestive, osmoregula-tory, central nervous, respiratory, or circulatory systems. The manu-brium is a stalk-like structure hanging down from the centre of the underside, with the mouth at its tip. This opens into the gastrovas-cular cavity, where digestion takes place and nutrients are absorbed. It is joined to the radial canals which extend to the margin of the bell.[17] Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement, but can use their hydrostatic skeleton to navi-gate through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are mostly passive.[citation needed] The body is composed of over 95% water; most of the umbrella mass is a gelatinous material — the jelly — called mesoglea which is sur-rounded by two layers of protective skin. The top layer is called the epidermis, and the inner layer is referred to as gastrodermis, which lines the gut.

Anatomy

Medusa jellyfish are a life stage exhibited in some species of the phylum Cnidaria. Medusa jelly-fish belong exclusively to Meduso-zoa, the clade of cnidarians which excludes Anthozoa (e.g., corals and anemones). This suggests that the medusa form evolved after the polyps.[32]The phylogenetics of this group are complex and still being worked out. The Medusozoa appear to be a sister group to Octocorallia.[33] Staurozoa appears to be the earliest diverging; Cubozoa and the coro-nate Scyphozoa form a clade that is the sister group of Hydrozoa plus discomedusan Scyphozoa. The Hydrozoa are the sister group of discomedusan Scyphozoa. Limno-medusae (Trachylina) is the sister group of hydroidolinans. This group may be the earliest diverging lineage among Hydrozoa. Semaeos-tomeae is a paraphyletic clade with Rhizostomeae. There are four major classes of medusozoan Cnidaria:Scyphozoa are often called true jellyfish. They have tetra-radial symmetry. They have tentacles around the outer margin of the bowl-shaped bell, and oral arms around the mouth.Cubozoa (box jellyfish) have a box-shaped bell, and their velarium assists them to swim more quickly. Box jellyfish may be related more closely to "true jellyfish" than either are to hydrozoa.[32]Hydrozoa may form medusa which resemble scyphozoans (but gener-ally with a velum) and are distin-guished by an absence of cells in the mesoglea. However, many hydrozoa species do not form medusa at all (such as hydra, which is hence not considered a jellyfish).Staurozoa (stalked jellyfish) do not have a polyp stage, however the medusa is generally sessile, ori-ented upside down and with a stalk from the "bell" planted to the sub-strate. Until recently, staurozoa was classified within scyphozoa.

Classification & Evolution

Most jellyfish alternate between polyp and medusa genera-tions during their life cycle. Addi-tionally, there are several possible larval life-stages. After fertilization a primitive free-swimming larval form, called the planula, develops. The planula is a small larva covered with cilia. It settles onto a firm surface and develops into a polyp. Some polyps can also asexually produce a creep-ing frustule larval form, which then also develops into a new polyp.The polyp is generally a small planted stalk with a mouth that is ringed by upward-facing tentacles. The polyps are like miniatures of the closely related anthozoan (sea anemones and corals) polyps, which are also members of Cni-daria. The jellyfish polyp may be sessile, living on the bottom or another substrate such as floats or boat hulls, or it may be free-floating or attached to tiny bits of free-living plankton[37] or rarely, fish[38] or other invertebrates. Polyps may be solitary or colonial. Polyp colonies form by strobilation, resulting in multiple polyps which share a common stomach cavity.[39] Most polyps are very small, measured in millimeters. They feed continuously. The polyp stage may last for years.Eventually the polyp gives rise to the medusa stage. New medusae are usually created asexually by strobilation or budding from the polyp. The medusa is the life stage which is most typically identified as a jellyfish.

Lifecycle

Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jelly-fish have roamed the seas for at least 500 mil-lion years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal.

About The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclu-sively to the non-polyp life-stage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing ten-tacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example cteno-phores (members from another phylum of common, gelatinous and generally transparent or translucent, free-swimming planktonic carni-vores now known as comb jellies) were included as "jellyfishes".[4] Even some scientists include the phylum ctenophora when they are referring to jellyfish.[5] Other scientists prefer to use the more all-encompassing term gelatinous zoo-plankton, when referring to these, together with other soft-bodied animals in the water column.[6] As jellyfish are not vertebrates, let alone true fish, the word jellyfish is considered by some to be a misnomer. Public aquariums may use the terms jellies or sea jellies instead.[7] Some sources may use the term "jelly" to refer to organisms in this taxon, as "jellyfish" may be considered inappropriate.[8]Many textbooks and sources refer to only scy-phozoa as "true jellyfish".[9][10]A group of jellyfish is sometimes called a bloom or a swarm.[11] "Bloom" is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, refer-ring to seasonal increases, or numbers beyond what was expected.[12] Another collective name for a group of jellyfish is a smack,[13] although this term is not commonly used by scientists who study jellyfish. Jellyfish are "bloomy" by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large numbers, even when an ecosystem is in balance.[14] Using "swarm" usually implies some kind of active ability to stay together, which a few species such as Aurelia, the moon jelly, demonstrate.[15]Medusa jellyfish may be classified as scyphome-dusae ("true" jellyfish), stauromedusae (stalked jellyfish), cubomedusae (box jellyfish), or hydro-medusae, according to which clade their species belongs.[16]In biology, a medusa (plural: medusae) is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below. The upper or aboral surface is called the exumbrella and the lower surface is called the subumbrella; the mouth is located on the lower surface, which may be partially closed by a membrane extending inward from the margin (called the velum). The digestive cavity consists of the gastrovascular cavity and radiating canals which extend toward the margin; these canals may be simple or branching, and vary in number from few to many. The margin of the disk bears

Terminology

Anatomy

JellyfishAbout Terminology Anatomy

Classification &

EvolutionLifecycle Ecology Relationship

to HumanTaxonomy Haeckel’s

Medusae

Jellyfish or jellies are the major non-polyp form of individu-als of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while sting-ing tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwa-ter. Large, often colorful, jellyfish are common in coastal zones world-wide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal.

About

The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp life-stage which occurs in many cnidar-ians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals shar-ing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transpar-ent or translucent, free-swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes".[4] Even some scien-tists include the phylum ctenophora when they are referring to jellyfish.[5] Other scientists prefer to use the more all-encompassing term gelatinous zooplankton, when referring to these, together with other soft-bodied animals in the water column.[6] As jellyfish are not verte-brates, let alone true fish, the word jellyfish is considered by some to be a misnomer. Public aquariums may use the terms jellies or sea jellies instead.[7] Some sources may use the term "jelly" to refer to organ-isms in this taxon, as "jellyfish" may be considered inappropriate.[8]Many textbooks and sources refer to only scyphozoa as "true jellyfish".[9][10]A group of jellyfish is sometimes called a bloom or a swarm.[11] "Bloom" is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, referring to sea-sonal increases, or numbers beyond what was expected.[12] Another collective name for a group of jelly-fish is a smack,[13] although this term is not commonly used by scientists who study jellyfish. Jelly-fish are "bloomy" by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large num-

Terminology

Most jellyfish do not have specialized digestive, osmoregula-tory, central nervous, respiratory, or circulatory systems. The manu-brium is a stalk-like structure hanging down from the centre of the underside, with the mouth at its tip. This opens into the gastrovas-cular cavity, where digestion takes place and nutrients are absorbed. It is joined to the radial canals which extend to the margin of the bell.[17] Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement, but can use their hydrostatic skeleton to navi-gate through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are mostly passive.[citation needed] The body is composed of over 95% water; most of the umbrella mass is a gelatinous material — the jelly — called mesoglea which is sur-rounded by two layers of protective skin. The top layer is called the epidermis, and the inner layer is referred to as gastrodermis, which lines the gut.

Anatomy

JellyfishAbout Terminology Anatomy

Classification &

EvolutionLifecycle Ecology Relationship

to HumanTaxonomy Haeckel’s

Medusae

Jellyfish or jellies are the major non-polyp form of individu-als of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while sting-ing tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwa-ter. Large, often colorful, jellyfish are common in coastal zones world-wide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal.

About

The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp life-stage which occurs in many cnidar-ians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals shar-ing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transpar-ent or translucent, free-swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes".[4] Even some scien-tists include the phylum ctenophora when they are referring to jellyfish.[5] Other scientists prefer to use the more all-encompassing term gelatinous zooplankton, when referring to these, together with other soft-bodied animals in the water column.[6] As jellyfish are not verte-brates, let alone true fish, the word jellyfish is considered by some to be a misnomer. Public aquariums may use the terms jellies or sea jellies instead.[7] Some sources may use the term "jelly" to refer to organ-isms in this taxon, as "jellyfish" may be considered inappropriate.[8]Many textbooks and sources refer to only scyphozoa as "true jellyfish".[9][10]A group of jellyfish is sometimes called a bloom or a swarm.[11] "Bloom" is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, referring to sea-sonal increases, or numbers beyond what was expected.[12] Another collective name for a group of jelly-fish is a smack,[13] although this term is not commonly used by scientists who study jellyfish. Jelly-fish are "bloomy" by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large num-

Terminology

Most jellyfish do not have specialized digestive, osmoregula-tory, central nervous, respiratory, or circulatory systems. The manu-brium is a stalk-like structure hanging down from the centre of the underside, with the mouth at its tip. This opens into the gastrovas-cular cavity, where digestion takes place and nutrients are absorbed. It is joined to the radial canals which extend to the margin of the bell.[17] Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement, but can use their hydrostatic skeleton to navi-gate through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are mostly passive.[citation needed] The body is composed of over 95% water; most of the umbrella mass is a gelatinous material — the jelly — called mesoglea which is sur-rounded by two layers of protective skin. The top layer is called the epidermis, and the inner layer is referred to as gastrodermis, which lines the gut.

Anatomy

JellyfishAbout Terminology Anatomy

Classification &

EvolutionLifecycle Ecology Relationship

to HumanTaxonomy Haeckel’s

Medusae

Jellyfish or jellies are the major non-polyp form of individu-als of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while sting-ing tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwa-ter. Large, often colorful, jellyfish are common in coastal zones world-wide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal.

About

The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclusively to the non-polyp life-stage which occurs in many cnidar-ians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals shar-ing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transpar-ent or translucent, free-swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes".[4] Even some scien-tists include the phylum ctenophora when they are referring to jellyfish.[5] Other scientists prefer to use the more all-encompassing term gelatinous zooplankton, when referring to these, together with other soft-bodied animals in the water column.[6] As jellyfish are not verte-brates, let alone true fish, the word jellyfish is considered by some to be a misnomer. Public aquariums may use the terms jellies or sea jellies instead.[7] Some sources may use the term "jelly" to refer to organ-isms in this taxon, as "jellyfish" may be considered inappropriate.[8]Many textbooks and sources refer to only scyphozoa as "true jellyfish".[9][10]A group of jellyfish is sometimes called a bloom or a swarm.[11] "Bloom" is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, referring to sea-sonal increases, or numbers beyond what was expected.[12] Another collective name for a group of jelly-fish is a smack,[13] although this term is not commonly used by scientists who study jellyfish. Jelly-fish are "bloomy" by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large num-

Terminology

Jellyfish

About Terminology AnatomyClassification

& Evolution

Lifecycle Ecology Relationship to Human

Taxonomy Haeckel’sMedusae

Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years,[1] and possibly 700 million years or more, making them the oldest multi-organ animal.

About

The term medusa was coined by Linnaeus in 1752, alluding to the tentacled head of Medusa in Greek mythology.[3] This term refers exclu-sively to the non-polyp life-stage which occurs in many cnidarians, which is typified by a large pulsating gelatinous bell with long trailing tentacles. All medusa-producing species belong to the sub-phylum Medusozoa. The English popular name jellyfish has been in use since 1796.[3] It has traditionally also been applied to other animals sharing a superficial resemblance, for example ctenophores (members from another phylum of common, gelatinous and generally transparent or translucent, free-swimming planktonic carnivores now known as comb jellies) were included as "jellyfishes".[4] Even some scientists include the phylum cte-nophora when they are referring to jellyfish.[5] Other scientists prefer to use the more all-encompassing term gelatinous zooplankton, when refer-ring to these, together with other soft-bodied animals in the water column.[6] As jellyfish are not vertebrates, let alone true fish, the word jellyfish is considered by some to be a misnomer. Public aquariums may use the terms jellies or sea jellies instead.[7] Some sources may use the term "jelly" to refer to organisms in this taxon, as "jellyfish" may be considered inappropriate.[8]Many textbooks and sources refer to only scyphozoa as "true jellyfish".[9][10]A group of jellyfish is sometimes called a bloom or a swarm.[11] "Bloom" is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, referring to seasonal increases, or num-bers beyond what was expected.[12] Another collective name for a group of jellyfish is a smack,[13] although this term is not commonly used by scien-tists who study jellyfish. Jellyfish are "bloomy" by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large numbers, even when an ecosystem is in balance.[14] Using "swarm" usually implies some kind of active ability to stay together, which a few species such as Aurelia, the moon jelly, demonstrate.[15]Medusa jellyfish may be classified as scyphomedusae ("true" jellyfish), stauromedusae (stalked jellyfish), cubomedusae (box jellyfish), or hydro-medusae, according to which clade their species belongs.[16]In biology, a medusa (plural: medusae) is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below. The upper or aboral surface is called the exum-brella and the lower surface is called the subumbrella; the mouth is located on the lower surface, which may be partially closed by a membrane extend-ing inward from the margin (called the velum). The digestive cavity con-sists of the gastrovascular cavity and radiating canals which extend toward the margin; these canals may be simple or branching, and vary in number from few to many. The margin of the disk bears sensory organs and ten-tacles as its said.German biologist Ernst Haeckel popularized medusae through his vivid illustrations, particularly in Kunstformen der Natur.

Jellyfish

About Terminology AnatomyClassification

& Evolution

Lifecycle Ecology Relationship to Human

Taxonomy Haeckel’sMedusae

Terminology