Sea butterfly
Encyclopedia
Sea butterflies, also known as Thecosomata or flapping snail
s, are a taxonomic suborder of small pelagic swimming sea snail
s. These are holoplankton
ic opisthobranch gastropod mollusks in the informal group Opisthobranchia
. They include some of the world's most abundant gastropod species.
This group is included in the pteropods, with its sister group the Gymnosomata. The validity of this clade is not unanimously established; whilst it had fallen out of favour, recent molecular evidence suggests that the taxon should be resurrected. The word pteropod applies both to the sea butterflies in the clade
Thecosomata and also to the sea angel
s in the clade Gymnosomata. Most Thecosomata have a calcified shell, whereas mature Gymnosomata do not.
have disappeared in several families. Their foot has taken the form of two wing-like lobes, or parapodia, which propel this little animal through the sea by slow flapping movements. They are rather difficult to observe, since the shell (when present) is mostly colorless, very fragile and usually less than 1 cm in length. Although their shell may be so fine as to be transparent, it is nevertheless calcareous
; their shells are bilaterally symmetric and can vary widely in shape: coiled, needle-like, triangular, globulous.
The shell is present in all stages of the Cavolinioidea (euthecosomata) life cycle, whereas in the Cymbulioidea (pseudothecosomata), adult Peraclididae bear shells, Cymbuliidae shed their larval shells and develop a cartilaginous pseudoconch in adulthood, and Desmopteridaen adults lack any rigid structure.
ic; that is, they spend their whole life in a planktonic form, rather than just being planktonic during the larva
l stage, as is more commonly the case in many marine
gastropods, whose veliger
larvae are part of the meroplankton
.
Little is known about the behaviour of sea butterflies, but they are known to have a peculiar way of feeding. At times, they just float along, ventral-side up, with the currents. They are mostly passive plankton
feeders, but at times they can be real hunters. They are generally herbivorous, entangling planktonic food through a mucous
web that can be up to 5 cm wide, many times larger than themselves. If disturbed, they abandon the net and flap slowly away. When descending to deeper water, they hold their wings up. Sometimes, they swarm in large numbers and can be found washed up in flotsam, especially along the coast of eastern Australia
.
Every day, they migrate vertically in the water column, following their planktonic prey. At night they hunt at the surface and return to deeper water in the morning.
in the Cenozoic
Era.
The group is represented in the fossil record from shells of those groups within the clade that mineralized. These shells are a major contributor to the carbonate cycle, making up as much as 12% of global carbonate flux. However the low stability of their aragonitic shells means that few end up being preserved in sediments, these being in shallower waters of the tropical oceans.
Aragonitic thecostomes have been predicted, under the IPCC's "business as usual" scenario, to become regionally extinct as soon as 2050.
(2005) Thecosomata is treated differently :
Clade Thecosomata :
The superfamily Limacinoidea becomes redundant and the family Limacinidae becomes part of the superfamily Cavolinioidea. The families Creseidae and Cuvierinidae become the subfamilies Creseinae and Cuvierininae. The infraorder Pseudothecosomata becomes the superfamily Cymbulioidea. The superfamily Peraclidoidea becomes redundant and the family Peraclididae is included in the superfamily Cymbulioidea as the family Peraclidae.
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s, are a taxonomic suborder of small pelagic swimming sea snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s. These are holoplankton
Holoplankton
Holoplankton are organisms that are planktonic for their entire life cycle. Examples of holoplankton include some diatoms, radiolarians, some dinoflagellates, foraminifera, amphipods, krill, copepods, and salps.-Sources:Asexual Holoplankton:...
ic opisthobranch gastropod mollusks in the informal group Opisthobranchia
Opisthobranchia
Opisthobranchs are a large and diverse group of specialized complex marine gastropods previously united under Opisthobranchia within the Heterobranchia, but no longer considered to represent a monophyletic grouping...
. They include some of the world's most abundant gastropod species.
This group is included in the pteropods, with its sister group the Gymnosomata. The validity of this clade is not unanimously established; whilst it had fallen out of favour, recent molecular evidence suggests that the taxon should be resurrected. The word pteropod applies both to the sea butterflies in the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Thecosomata and also to the sea angel
Sea angel
Sea angels previously known as one kind of pteropod, are a large group of small swimming sea slugs in six different families. These are pelagic marine opisthobranch gastropod molluscs in the clade Gymnosomata within the larger clade Heterobranchia....
s in the clade Gymnosomata. Most Thecosomata have a calcified shell, whereas mature Gymnosomata do not.
Morphology
These snails float and swim freely in the water, and are carried along with the currents. This has led to a number of adaptations in their bodies. The shell and the gillGill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
have disappeared in several families. Their foot has taken the form of two wing-like lobes, or parapodia, which propel this little animal through the sea by slow flapping movements. They are rather difficult to observe, since the shell (when present) is mostly colorless, very fragile and usually less than 1 cm in length. Although their shell may be so fine as to be transparent, it is nevertheless calcareous
Calcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
; their shells are bilaterally symmetric and can vary widely in shape: coiled, needle-like, triangular, globulous.
The shell is present in all stages of the Cavolinioidea (euthecosomata) life cycle, whereas in the Cymbulioidea (pseudothecosomata), adult Peraclididae bear shells, Cymbuliidae shed their larval shells and develop a cartilaginous pseudoconch in adulthood, and Desmopteridaen adults lack any rigid structure.
Behaviour
Thecosomata beat their wing-like parapodia to "fly" through the water. They are holoplanktonHoloplankton
Holoplankton are organisms that are planktonic for their entire life cycle. Examples of holoplankton include some diatoms, radiolarians, some dinoflagellates, foraminifera, amphipods, krill, copepods, and salps.-Sources:Asexual Holoplankton:...
ic; that is, they spend their whole life in a planktonic form, rather than just being planktonic during the larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
l stage, as is more commonly the case in many marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
gastropods, whose veliger
Veliger
A veliger is the planktonic larva of many kinds of marine and freshwater gastropod molluscs, as well as most bivalve mollusks.- Description :...
larvae are part of the meroplankton
Meroplankton
Meroplankton are organisms that are planktonic for only a part of their life cycles, usually the larval stage. Examples of meroplankton include the larvae of sea urchins, sea stars, crustaceans, marine worms, some marine gastropods and most fish....
.
Little is known about the behaviour of sea butterflies, but they are known to have a peculiar way of feeding. At times, they just float along, ventral-side up, with the currents. They are mostly passive plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
feeders, but at times they can be real hunters. They are generally herbivorous, entangling planktonic food through a mucous
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
web that can be up to 5 cm wide, many times larger than themselves. If disturbed, they abandon the net and flap slowly away. When descending to deeper water, they hold their wings up. Sometimes, they swarm in large numbers and can be found washed up in flotsam, especially along the coast of eastern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
Distribution
Thecosomata are most common (in terms of diversity, species richness, and abundance) in the top 25 metres (82 ft) of the ocean, and become rarer the deeper one samples. They migrate vertically from day to night, so the community structure changes on a 24 h cycle; during the day many organisms take refuge at water depths in excess of 100 m. They range from the tropics to the poles.Every day, they migrate vertically in the water column, following their planktonic prey. At night they hunt at the surface and return to deeper water in the morning.
Fossil record
This is, geologically-speaking, rather a young group, having evolved from the Late PaleocenePaleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
in the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
Era.
The group is represented in the fossil record from shells of those groups within the clade that mineralized. These shells are a major contributor to the carbonate cycle, making up as much as 12% of global carbonate flux. However the low stability of their aragonitic shells means that few end up being preserved in sediments, these being in shallower waters of the tropical oceans.
Importance in the food chain
These creatures, which are about the size of a lentil, are eaten by various marine species, including a wide variety of fish that are, in turn, consumed by penguins and polar bears. They form the sole food source of their relatives, the Gymnosomata. They are also consumed by sea birds, whales, and commercially important fish, which they can render unsaleable if consumed in large quantities.Vulnerability to increased concentrations
Increased levels of atmospheric could, by increasing oceanic acidity, threaten the survival of shell-forming thecostomes.Aragonitic thecostomes have been predicted, under the IPCC's "business as usual" scenario, to become regionally extinct as soon as 2050.
Ponder & Lindberg
Order Thecosomata de Blainville, 1824- Infraorder Euthecosomata
- Superfamily Limacinoidea
- Family LimacinidaeLimacinidaeLimacinidae is a family of small sea snails, pteropods, pelagic marine gastropod mollusks in the clade Thecosomata .-Genera:Genera within the family Limacinidae include:...
de Blainville, 1823
- Family Limacinidae
- Superfamily CavolinioideaCavolinioideaThe superfamily Cavolinioidea is the most speciose group of sea butterflies. Sea butterflies are pelagic marine gastropods, so called because they swim by flapping their wing-like parapodia.-Distribution:...
- Family CavoliniidaeCavoliniidaeThe family Cavoliniidae is a taxonomic group of small floating sea snails, pelagic marine opisthobranch gastropod mollusks. This family is part of a larger group which is commonly known as the sea butterflies because they swim by flapping what appear to be small "wings".-Distribution:This family of...
H. and A. Adams, 1854 - Family Clioidae
- Family Creseidae
- Family Cuvierinidae
- Family PraecuvierinidaePraecuvierinidaePraecuvierinidae is a family of extinct of small floating sea snails, pelagic marine opisthobranch gastropod mollusks in the superfamily Cavolinioidea.- Genera :* Genus Praecuvierina Janssen, 2005...
- Family Cavoliniidae
- Superfamily Limacinoidea
- Infraorder Pseudothecosomata
- Superfamily Peraclidoidea
- Family PeraclidaePeraclidaePeraclidae is a family of pelagic sea snails or "sea butterflies", marine gastropod mollusks in the superfamily Cymbulioidea.This family has no subfamilies ....
Tesch, 1913
- Family Peraclidae
- Superfamily CymbulioideaCymbulioideaCymbulioidea is a taxonomic superfamily of pelagic "sea butterflies". These are holoplanktonic opisthobranch molluscs in the clade Thecosomata.-Anatomy:...
- Family CymbuliidaeCymbuliidaeCymbuliidae is a family of pelagic sea snails or "sea butterflies", marine gastropod mollusks in the superfamily Cymbulioidea.- Description :...
GrayJohn Edward GrayJohn Edward Gray, FRS was a British zoologist. He was the elder brother of George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray ....
, 1840 - Family DesmopteridaeDesmopteridaeDesmopteridae is a family of pelagic sea snails or "sea butterflies", marine gastropod mollusks in the superfamily Cymbulioidea.This family has no subfamilies ....
Dall, 1921
- Family Cymbuliidae
- Superfamily Peraclidoidea
Bouchet & Rocroi
In the new taxonomy of Bouchet & RocroiTaxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi is currently the most up-to-date overall system for classifying gastropod mollusks...
(2005) Thecosomata is treated differently :
Clade Thecosomata :
- Superfamily Cavolinioidea Gray, 1850 ( = Euthecosomata)
- Family Cavoliniidae Gray, 1850 (1815)
- Subfamily Cavoliinae Gray, 1850 (1815) (formerly Hyalaeidae Rafinesque, 1815 )
- Subfamily Clioinae Jeffreys, 1869 (formerly Cleodoridae Gray, 1840 - nomen oblitum)
- Subfamily Cuvierininae van der Spoel, 1967 (formerly : Cuvieriidae Gray, 1840 (nom. inv.); Tripteridae Gray, 1850 )
- Subfamily Creseinae Curry, 1982
- Family Limacinidae Gray, 1840 (formerly : Spirialidae Chenu, 1859 ; Spiratellidae Dall, 1921 )
- † Family Sphaerocinidae A. Janssen & Maxwell, 1995
- Family Cavoliniidae Gray, 1850 (1815)
- Superfamily Cymbulioidea Gray, 1840 ( = Pseudothecosomata)
- Family Cymbuliidae Gray, 1840
- Subfamily Cymbuliinae Gray, 1840
- Subfamily Glebinae van der Spoel, 1976
- Family Desmopteridae Chun, 1889
- Family Peraclidae Tesch, 1913 (formerly Procymbuliidae Tesch, 1913
- Family Cymbuliidae Gray, 1840
The superfamily Limacinoidea becomes redundant and the family Limacinidae becomes part of the superfamily Cavolinioidea. The families Creseidae and Cuvierinidae become the subfamilies Creseinae and Cuvierininae. The infraorder Pseudothecosomata becomes the superfamily Cymbulioidea. The superfamily Peraclidoidea becomes redundant and the family Peraclididae is included in the superfamily Cymbulioidea as the family Peraclidae.
See also
- Ocean acidificationOcean acidificationOcean acidification is the name given to the ongoing decrease in the pH and increase in acidity of the Earth's oceans, caused by the uptake of anthropogenic carbon dioxide from the atmosphere....
- Pteropoda Fact Sheet