The chondrophores or porpitids are a small group of

hydrozoa Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specializ ...

ns in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Porpitidae. Though it derives from an outdated name for this lineage (see

below Below may refer to: *Earth *Ground (disambiguation) *Soil *Floor *Bottom (disambiguation) Bottom may refer to: Anatomy and sex * Bottom (BDSM), the partner in a BDSM who takes the passive, receiving, or obedient role, to that of the top or ...

), some still find the term "chondrophore" useful as a synonym to "porpitid" in discussions of the two

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

contained therein. They all live at the surface of the open ocean, and are colonies of carnivorous, free-floating hydroids whose role in the plankton community is similar to that of pelagic jellyfish. The chondrophores look like a single

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...

but are actually colonial animals, made up of orderly cooperatives of polyps living under specialized sail-structures. The most familiar members of the family Porpitidae are the blue button (''

Porpita porpita ''Porpita porpita'', or blue button, is a marine organism consisting of a colony of hydroids found in the warmer, tropical and sub-tropical waters of the Pacific, Atlantic, and Indian oceans, as well as the Mediterranean Sea and eastern Arabian ...

'') and the

by-the-wind sailor ''Velella'' is a monospecific genus of hydrozoa in the Porpitidae family. Its only known species is ''Velella velella'', a cosmopolitan free-floating hydrozoan that lives on the surface of the open ocean. It is commonly known by the names sea raf ...

(''Velella velella'').

Description

The tiny individual animals are specialized to perform specific tasks; some form the central

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

-filled disc (which is a golden brown colour and hardened by

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

ous material) essential to keeping the colony afloat; others form radiating tentacles for tasks such as catching prey,

reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...

, and

digestion Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intest ...

. Microplankton is a chondrophore's principal prey. Although none have powerful stings, contact with the skin may cause irritation. At the mercy of winds and currents, chondrophores are

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

and drift in the open

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

. They are often seen in large aggregations; mass beachings are not unusual. Chondrophores multiply by releasing tiny (0.3-2.5 millimetres or 0.01-0.09 inches)

medusa In Greek mythology, Medusa (; Ancient Greek: Μέδουσα "guardian, protectress"), also called Gorgo, was one of the three monstrous Gorgons, generally described as winged human females with living venomous snakes in place of hair. Those ...

e which go on to develop new colonies. ''

Velella ''Velella'' is a monospecific genus of hydrozoa in the Porpitidae family. Its only known species is ''Velella velella'', a cosmopolitan free-floating hydrozoan that lives on the surface of the open ocean. It is commonly known by the names sea raf ...

'' differs from ''

Porpita ''Porpita'' is genus of hydrozoans in the family Porpitidae. It has two species recognized and is the type genus of its family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinit ...

'' by their transparent, membranous sail-shaped floats; filled with gas, the membranes have a texture reminiscent of

cellophane Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria, and liquid water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated w ...

. Both genera have

turquoise Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminium, with the chemical formula . It is rare and valuable in finer grades and has been prized as a gemstone and ornamental stone for thousands of yea ...

to dark blue mantles and tentacles, with lemon-yellow morphs occasionally encountered. Neither group is particularly large: the floats of ''Velella'' are usually under 7.6 centimetres (3 inches) in diameter, while those of ''Porpita'' are usually less than 3.8 centimetres (1.5 inches).

Systematics

The order Chondrophora was created by A.K. Totton in 1954 to accommodate these unusual genera of Hydrozoa as their taxonomic affinities were unclear. They had previously been placed either in the

Anthomedusae Anthoathecata, or the athecate hydroids, are an order of hydrozoans belonging to the phylum Cnidaria. A profusion of alternate scientific names exists for this long-known, heavily discussed, and spectacular group. It has also been called Gymnobl ...

(also known as Athecata) or the

Siphonophorae Siphonophorae (from Greek ''siphōn'' 'tube' + ''pherein'' 'to bear') is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 specie ...

, and though many accepted Totton's placement, a considerable number of authors maintained them in the Anthomedusae/Athecata all the time. By the 1970s/1980s, nearly all Hydrozoan systematists were in agreement that these genera did indeed belong in that group and the order Chondrophora became defunct, replaced by the

Porpitidae, which took priority over the more recent name ''Velellidae'' (the group was subdivided into these two families when still ranked as an order). In modern classifications, the Porpitidae are included in the

hydrozoan Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialize ...

suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

Capitata Capitata is a suborder of Hydrozoa, a class of marine invertebrates belonging to the phylum Cnidaria. Characteristics Members of this suborder are characterised by the tentacles of the polyps terminating in knobs. In some species these are o ...

. They are believed to have originated in the late

Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided ...

period, some 650-540

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

. A rare soft-bodied

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

that was recovered from the Farmers Member of the Borden Formation (

Mississippian age The Mississippian ( , also known as Lower Carboniferous or Early Carboniferous) is a subperiod in the geologic timescale or a subsystem of the geologic record. It is the earlier of two subperiods of the Carboniferous period lasting from roughly ...

) in northeastern Kentucky was interpreted as a chondrophorine float and potential porpitids were described from the Carrara Formation (lower Cambrian) of California.Bruce S. Lieberman et al. 2017. Disc-shaped fossils resembling porpitids or eldonids from the early Cambrian (Series 2: Stage 4) of western U.S.A.,

PeerJ ''PeerJ'' is an open access peer-reviewed scientific mega journal covering research in the biological and medical sciences. It is published by a company of the same name that was co-founded by CEO Jason Hoyt (formerly at Mendeley) and publisher Pet ...

,

/ref>

Footnotes

References

* (1970): Anthomedusae/Athecatae (Hydrozoa, Cnidaria) of the Mediterranean. Part I. Capitata. ''Fauna e Flora del Golfo di Napoli'' 39: 1-96, 11 plates. * (2008)
The Hydrozoa Directory

Retrieved 2008-JUL-08. * (1954): Siphonophora of the Indian Ocean together with systematic and biological notes on related specimens from other oceans. ''Discovery Reports'' 27: 1-162.

External links

{{Taxonbar, from=Q146655 Porpitidae