Siphonophora
Encyclopedia
Siphonophorae or Siphonophora, the siphonophores, are an order
of the Hydrozoa
, a class of marine invertebrate
s belonging to the phylum Cnidaria
. They are colonial
, but the colonies can superficially resemble jellyfish
; although they appear to be a single organism
, each specimen is actually a colony of Siphonophora. The best known species is the dangerous Portuguese Man o' War
(Physalia physalis). With a body length of 40–50 m, another species of siphonophore, Praya dubia
, is one of the longest animals in the world.
and polyp
oid zooids
that are morphologically
and functionally specialized. Each zooid is an individual, but their integration with each other is so strong that the colony attains the character of one large organism. Indeed, most of the zooids are so specialized that they lack the ability to survive on their own. Siphonophorae thus exist at the boundary between colonial and complex multicellular organisms. Also, because multicellular organisms have cells which, like zooids, are specialized and interdependent, siphonophores may provide clues regarding their evolution
.
Like other hydrozoa
ns, certain siphonophores can emit light. A siphonophore of the genus
Erenna has been discovered at a depth of around 1,600 meters off the coast of Monterey, California
. The individuals from these colonies are strung together like a feather boa
. They prey on small animals using stinging cells. Among the stinging cells are stalks with red glowing ends. The tips twitch back and forth creating a twinkling effect. It is theorized that twinkling red light attracts small fish that have been found eaten by these siphonophores. While many sea animals produce blue and green bioluminescence
, this siphonophore was only the second lifeform found to produce a red light (the first being the scaleless dragonfish Chirostomias pliopterus).
Due to their highly specialized colonies, siphonophores have long misled scientists. They were for a long time believed to be a highly distinct group, but now are known to have evolved from simpler colonial hydrozoans similar to Anthomedusae
or Leptomedusae
. Consequently, they are now united with these in a subclass
Leptolinae
.
The Siphonophorae have long fascinated scientists and layfolk alike, due to their dramatic appearance as well as the large size and dangerous sting of several species
. Compared to their relatives, their systematics
are relatively straightforward:
Suborder Calycophorae
Suborder Cystonectae
Suborder Physonectae
The genus Stepanyantsia is of unclear affiliations; it might belong in the Agalmatidae.
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of the Hydrozoa
Hydrozoa
Hydrozoa are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater...
, a class of marine invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s belonging to the phylum Cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...
. They are colonial
Colony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...
, but the colonies can superficially resemble jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
; although they appear to be a single organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
, each specimen is actually a colony of Siphonophora. The best known species is the dangerous Portuguese Man o' War
Portuguese Man o' War
The Portuguese Man o' War , also known as the Portuguese man-of-war, man-of-war, or bluebottle, is a jelly-like marine invertebrate of the family Physaliidae...
(Physalia physalis). With a body length of 40–50 m, another species of siphonophore, Praya dubia
Praya dubia
Praya dubia, or the Giant Siphonophore, is a deep sea organism , a member of the Hydrozoa. With a body length of 40–50m, Praya dubia is one of the largest invertebrates...
, is one of the longest animals in the world.
Description
Siphonophores are especially scientifically interesting because they are composed of medusoidMedusa (biology)
In biology, a medusa 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...
and polyp
Polyp
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are approximately cylindrical in shape and elongated at the axis of the body...
oid zooids
Bryozoa
The Bryozoa, also known as Ectoprocta or commonly as moss animals, are a phylum of aquatic invertebrate animals. Typically about long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia...
that are morphologically
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
and functionally specialized. Each zooid is an individual, but their integration with each other is so strong that the colony attains the character of one large organism. Indeed, most of the zooids are so specialized that they lack the ability to survive on their own. Siphonophorae thus exist at the boundary between colonial and complex multicellular organisms. Also, because multicellular organisms have cells which, like zooids, are specialized and interdependent, siphonophores may provide clues regarding their evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
.
Like other hydrozoa
Hydrozoa
Hydrozoa are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater...
ns, certain siphonophores can emit light. A siphonophore of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Erenna has been discovered at a depth of around 1,600 meters off the coast of Monterey, California
Monterey, California
The City of Monterey in Monterey County is located on Monterey Bay along the Pacific coast in Central California. Monterey lies at an elevation of 26 feet above sea level. As of the 2010 census, the city population was 27,810. Monterey is of historical importance because it was the capital of...
. The individuals from these colonies are strung together like a feather boa
Feather boa
A feather boa is a fashion accessory that is usually worn wrapped around the neck like a scarf.-Construction:A boa can be made of fur, but it is usually made instead from various types of feathers. Ostrich, marabou, chandelle, and turkey are the most common feathers used, although non-feather boas...
. They prey on small animals using stinging cells. Among the stinging cells are stalks with red glowing ends. The tips twitch back and forth creating a twinkling effect. It is theorized that twinkling red light attracts small fish that have been found eaten by these siphonophores. While many sea animals produce blue and green bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
, this siphonophore was only the second lifeform found to produce a red light (the first being the scaleless dragonfish Chirostomias pliopterus).
Systematics
Anthomedusae
Anthomedusae or Anthomedusa, the athecate hydroids, are an order of the Hydrozoa, a class of marine invertebrates belonging to the phylum Cnidaria...
or Leptomedusae
Leptomedusae
Leptomedusae or Leptomedusa, commonly called thecate hydroids, are a cnidarian order in the subclass Leptolinae. They were formerly placed at suborder rank in the paraphyletic "Hydroida"...
. Consequently, they are now united with these in a subclass
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
Leptolinae
Leptolinae
Leptolinae are a cnidarian subclass of the Hydrozoa. They contain the bulk of the paraphyletic "Hydroida" which were one of the main groupings of the Hydrozoa in older classifications and were placed at order rank...
.
The Siphonophorae have long fascinated scientists and layfolk alike, due to their dramatic appearance as well as the large size and dangerous sting of several species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. Compared to their relatives, their systematics
Systematics
Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...
are relatively straightforward:
Suborder Calycophorae
- Family AbylidaeAbylidaeAbylidae is a family of marine invertebrates in the order Siphonophora. They are colonial, but the colonies can superficially resemble jellyfish; although they appear to be a single organism, each specimen is actually a colony of Siphonophora....
- Family Clausophyidae
- Family Diphyidae
- Family Hippopodiidae
- Family PrayidaePrayidaePrayidae is a family of marine invertebrates in the order Siphonophora. They are colonial, but the colonies can superficially resemble jellyfish; although they appear to be a single organism, each specimen is actually a colony of Siphonophora....
- Family Sphaeronectidae
Suborder Cystonectae
- Family Physaliidae
- Family Rhizophysidae
Suborder Physonectae
- Family AgalmatidaeAgalmatidaeAgalmatidea, or Agalmidae, is a family of siphonophores.-Genera:*Agalma Eschscholtz, 1825*Cordagalma Totton, 1932*Erenna Bedot, 1904*Frillagalma Daniel, 1966*Halistemma Huxley, 1859*Lychnagalma Haeckel, 1888...
- Family Apolemiidae
- Family Athorybiidae
- Family Erennidae
- Family Forskaliidae
- Family Physophoridae
- Family Pyrostephidae
- Family Rhodaliidae
The genus Stepanyantsia is of unclear affiliations; it might belong in the Agalmatidae.
External links
- http://siphonophores.org
- http://www.ville-ge.ch/musinfo/mhng/hydrozoa/sipho/siphonophora.htm
- http://www.youtube.com/watch?v=KT1TSbarW1U