Vetigastropoda
Encyclopedia
Vetigastropoda is a major taxonomic group of sea snail
s, marine
gastropod mollusks that form a very ancient lineage
. Taxonomically Vetigastropoda are sometimes treated as an order
although they are a clade
in Bouchet and Rocroi, 2005
.
Vetigastropods are considered to be among the most primitive living gastropods, and are widely distributed in all ocean
s of the world. Their habitats range from the deep sea
to intertidal zone
s. Many have shell
s with slits or other secondary openings. One of their main characteristics is the presence of intersected crossed platy shell structure. Most vetigastropods have some bilateral asymmetry of their organ
systems.
or Skeneoidea, to more than 11.8 in (300 mm) in length, as with the Haliotoidea
. External colours and patterns are typically drab, but such groups as the Tricolioidea and some Trochoidea
and Pleurotomarioidea
have bright colours and glossy shells. The clade is characterized by having an intersected crossed platy shell structure.
Shells range from elongate turret-shaped structures, to near-spherical. Shell sculpture varies greatly from simple concentric growth lines, which may or may not be barely visible on the shell surface, to heavy radial and axial ribbing. The shell aperture is normally oval, and often tangential to the coiling axis. Most species have an operculum
(a small lid-like organ). Within the shell, Vetigastropods have a single pair of cephalic tentacles, and a distinct snout containing the mouth. The lateral sides of the body typically have sensory epipodial tentacles.
areas, temperate regions, and under polar ice.
s and cold seeps.
, although some deep-sea varieties are hermaphrodites. Vetigastropods usually eject their gametes directly into the sea for fertilization, thus there is no courtship or mating between individuals for most species.
s, and sponges. Several species such as Haliotoidea
and Trochoidea
have evolved to feed directly on such plant material as algae
and marine angiosperms. Deep-sea vetigastropods typically consume sediment.
e. Many vetigastropods secrete egg
envelopes and have glandular pallial structures that produce masses of jelly-coated eggs.
Larger species typically have yearly cycles of spawning, and produce millions of eggs per reproductive season. Smaller species produce fewer eggs, but can spawn year round.
, although Bouchet & Rocroi, 2005
refer to this group simply as a clade, leaving taxonomic determination as a future option. The World Register of Marine Species (WoRMS) follows Bouchet & Rocroi regarding the taxonomic content of the Gastropoda but gives ranks to the higher taxa and defines Vetigastropoda as a subclass
Bouchet & Rocroi, 2005 treats the Vetigastropoda as a major clade and as a sister clade to the Caenogastropoda
but includes the Vetigastropoda in what are referred to as Basal taxa that are certainly Gastropoda. Ponder & Lindberg, 1997 previously assigned the Vetigastropoda, as a superorder, to the Subclass Orthogastropoda
.
Phylogenetic analysis indicates that this taxon
is one of the four natural groups within the Gastropoda: Vetigastropoda, Caenogastropoda
, Patellogastropoda
, and Heterobranchia
. Research on the mitochondrial genome
arrangement has shown that the Vetigastropoda (and Caenogastropoda) mostly retain the ancestral gene
arrangement.
Sea snail
Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....
s, 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...
gastropod mollusks that form a very ancient lineage
Lineage (evolution)
An evolutionary lineage is a sequence of species, that form a line of descent, each new species the direct result of speciation from an immediate ancestral species. Lineages are subsets of the evolutionary tree of life. Lineages are often determined by the techniques of molecular systematics.-...
. Taxonomically Vetigastropoda are sometimes treated as an order
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...
although they are a 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...
in Bouchet and Rocroi, 2005
Taxonomy 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...
.
Vetigastropods are considered to be among the most primitive living gastropods, and are widely distributed in all ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
s of the world. Their habitats range from the deep sea
Deep sea
The deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline and above the seabed, at a depth of 1000 fathoms or more. Little or no light penetrates this part of the ocean and most of the organisms that live there rely for subsistence on falling organic matter...
to intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
s. Many have shell
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
s with slits or other secondary openings. One of their main characteristics is the presence of intersected crossed platy shell structure. Most vetigastropods have some bilateral asymmetry of their organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
systems.
Description
Vetigastropods range in size from approximately 0.08 in (2 mm) long in the case of ScissurelloideaScissurelloidea
Scissurelloidea is a superfamily of minute sea snails, marine gastropod mollusks or micromollusks in the clade Vetigastropoda.-Taxonomy :This superfamily consists of two following families :*Family Scissurellidae Gray, 1847*Family Anatomidae McLean, 1989Geiger updated two other subfamilias to family...
or Skeneoidea, to more than 11.8 in (300 mm) in length, as with the Haliotoidea
Haliotoidea
Haliotoidea is a superfamily of sea snails, marine gastropod mollusks in the clade Vetigastropoda .- Families :...
. External colours and patterns are typically drab, but such groups as the Tricolioidea and some Trochoidea
Trochoidea (superfamily)
Trochoidea is a superfamily of small to very large vetigastropod sea snails with gills and an operculum.They have nacre as the inner shell layer...
and Pleurotomarioidea
Pleurotomarioidea
Pleurotomarioidea is a superfamily of small to large marine gastropods included in the Vetigastropoda.These are the slit shells, originally named Pleurotomariacea, in keeping with the convention for naming superfamilies at the time....
have bright colours and glossy shells. The clade is characterized by having an intersected crossed platy shell structure.
Shells range from elongate turret-shaped structures, to near-spherical. Shell sculpture varies greatly from simple concentric growth lines, which may or may not be barely visible on the shell surface, to heavy radial and axial ribbing. The shell aperture is normally oval, and often tangential to the coiling axis. Most species have an operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
(a small lid-like organ). Within the shell, Vetigastropods have a single pair of cephalic tentacles, and a distinct snout containing the mouth. The lateral sides of the body typically have sensory epipodial tentacles.
Distribution
Vetigastropods are distributed throughout all oceans of the world, including tropicalTropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
areas, temperate regions, and under polar ice.
Habitat
Vetigastropods are present in most marine environments from intertidal zones to the deep sea. They exist on rocky substrates, in soft sediments, and some have been found at deep-sea hydrothermal ventHydrothermal vent
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...
s and cold seeps.
Behaviour
Most vetigastropods are dioeciousDioecious
Dioecy is the property of a group of biological organisms that have males and females, but not members that have organs of both sexes at the same time. I.e., those whose individual members can usually produce only one type of gamete; each individual organism is thus distinctly female or male...
, although some deep-sea varieties are hermaphrodites. Vetigastropods usually eject their gametes directly into the sea for fertilization, thus there is no courtship or mating between individuals for most species.
Diet
Vetigastropods typically feed on such organisms as bryozoans, tunicateTunicate
Tunicates, also known as urochordates, are members of the subphylum Tunicata, previously known as Urochordata, a group of underwater saclike filter feeders with incurrent and excurrent siphons that is classified within the phylum Chordata. While most tunicates live on the ocean floor, others such...
s, and sponges. Several species such as Haliotoidea
Haliotoidea
Haliotoidea is a superfamily of sea snails, marine gastropod mollusks in the clade Vetigastropoda .- Families :...
and Trochoidea
Trochoidea (superfamily)
Trochoidea is a superfamily of small to very large vetigastropod sea snails with gills and an operculum.They have nacre as the inner shell layer...
have evolved to feed directly on such plant material as algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and marine angiosperms. Deep-sea vetigastropods typically consume sediment.
Reproduction
Vetigastropods normally have very small eggs that produce lecithotrophic (yolk feeding) or non-feeding larvaLarva
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...
e. Many vetigastropods secrete egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
envelopes and have glandular pallial structures that produce masses of jelly-coated eggs.
Larger species typically have yearly cycles of spawning, and produce millions of eggs per reproductive season. Smaller species produce fewer eggs, but can spawn year round.
Taxonomy
The Vetigastropoda have been referred to as a superorder as recently as at least 2007, by M. Harzhauser and in 2005 by D. Heidelberger and L. Koch following Ponder & Lindberg, 1997Taxonomy of the Gastropoda (Ponder & Lindberg, 1997)
The taxonomy of the Gastropoda, as revised by Winston Ponder and David R. Lindberg in 1997, is an older taxonomy of the class Gastropoda, the class of molluscs consisting of all snails and slugs...
, although Bouchet & Rocroi, 2005
Taxonomy 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...
refer to this group simply as a clade, leaving taxonomic determination as a future option. The World Register of Marine Species (WoRMS) follows Bouchet & Rocroi regarding the taxonomic content of the Gastropoda but gives ranks to the higher taxa and defines Vetigastropoda as a subclass
Bouchet & Rocroi, 2005 treats the Vetigastropoda as a major clade and as a sister clade to the Caenogastropoda
Caenogastropoda
Caenogastropoda is a taxonomic clade of a large diverse group of mostly marine gastropods.Caenogastropoda contains a majority of the families of shelled marine molluscs including such families as the periwinkles, cowries, wentletraps, moon snails, and cone snails.About 60% of all living gastropods...
but includes the Vetigastropoda in what are referred to as Basal taxa that are certainly Gastropoda. Ponder & Lindberg, 1997 previously assigned the Vetigastropoda, as a superorder, to the Subclass Orthogastropoda
Orthogastropoda
Orthogastropoda was a major taxonomic groupings of snails and slugs, an extremely large subclass within the huge class Gastropoda according to the older taxonomy of the Gastropoda ....
.
Phylogenetic analysis indicates that this taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
is one of the four natural groups within the Gastropoda: Vetigastropoda, Caenogastropoda
Caenogastropoda
Caenogastropoda is a taxonomic clade of a large diverse group of mostly marine gastropods.Caenogastropoda contains a majority of the families of shelled marine molluscs including such families as the periwinkles, cowries, wentletraps, moon snails, and cone snails.About 60% of all living gastropods...
, Patellogastropoda
Patellogastropoda
Patellogastropoda, common name true limpets and historically called Docoglossa, is a major phylogenetic group of marine gastropods, seen either as a clade or as a taxonomic order.-Taxonomy:Patellogastropoda was proposed by David R...
, and Heterobranchia
Heterobranchia
Heterobranchia, the heterobranchs or Euthyneura, is a taxonomic clade of snails and slugs, which includes species from the sea, the land and freshwater; marine, aquatic and terrestrial gastropod mollusks....
. Research on the mitochondrial genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
arrangement has shown that the Vetigastropoda (and Caenogastropoda) mostly retain the ancestral gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
arrangement.
Superfamilies
Superfamilies within the Vetigastropoda include:- Not assigned to a superfamily within Vetigastropoda are three families: family AtaphridaeAtaphridaeAtaphridae, common name the false top snails, is a family of sea snails, marine gastropod mollusks in the clade Vetigastropoda ....
, family PendromidaePendromidaePendromidae is a family of gastropods in the clade Vetigastropoda .This family is unassigned to superfamily...
and † family SchizogoniidaeSchizogoniidaeSchizogoniidae is an extinct family of gastropods in the clade Vetigastropoda .This family is unassigned to superfamily. This family has no subfamilies....
. - Superfamily AmberleyoideaAmberleyoideaAmberleyoidea is an extinct superfamily of small to large sea snails, marine gastropod mollusks in the clade Vetigastropoda....
- Superfamily AngarioideaAngarioideaAngarioidea is a superfamily of small sea snails, marine gastropod mollusks in the clade Vetigastropoda.-Taxonomy :The superfamily Angarioidea was created as a new superfamily by Williams et al...
(created as a new superfamily by Williams et al. (2008).) - Superfamily EotomarioideaEotomarioideaEotomarioidea is an extinct superfamily of small to large sea snails, marine gastropod mollusks in the clade Vetigastropoda.-Taxonomy :* † Family Eotomariidae Wenz, 1938 * † Family Gosseletinidae Wenz, 1938 * † Family Luciellidae Knight, 1956...
- Superfamily Fissurelloidea Flemming, 1822 - keyhole limpets
- Superfamily HaliotoideaHaliotoideaHaliotoidea is a superfamily of sea snails, marine gastropod mollusks in the clade Vetigastropoda .- Families :...
Rafinesque, 1815 - abalones - Superfamily LepetelloideaLepetelloideaLepetelloidea is a superfamily of sea snails, small deepwater limpets, marine gastropod mollusks in the clade Vetigastropoda...
- Superfamily LepetodriloideaLepetodriloideaLepetodriloidea is a superfamily of small to large sea snails, marine gastropod mollusks in the clade Vetigastropoda.-Families :Families within the superfamily Lepetodriloidea include:*Family Lepetodrilidae McLean, 1988*Family Clypeosectidae McLean, 1989...
McLean, 1988 - hydrothermal vent limpets - Superfamily MurchisonioideaMurchisonioideaMurchisonioidea is an extinct superfamily of small to large sea snails, marine gastropod mollusks in the clade Vetigastropoda.This superfamily was previously included in the Caenogastropoda by Ponder and Warén and by Bandel in studies published in 1993 and 1997. However, studies by Tracey et al. ...
- Superfamily NeomphaloideaNeomphaloideaNeomphaloidea is a superfamily of deep-sea snails or limpets, marine gastropod mollusks in the clade Vetigastropoda...
- Superfamily PleurotomarioideaPleurotomarioideaPleurotomarioidea is a superfamily of small to large marine gastropods included in the Vetigastropoda.These are the slit shells, originally named Pleurotomariacea, in keeping with the convention for naming superfamilies at the time....
Swainson, 1840 - slit snails - Superfamily PorcellioideaPorcellioideaPorcellioidea is an extinct superfamily of small to large sea snails, marine gastropod mollusks in the clade Vetigastropoda.This superfamily dates back to the Paleozoic. They developed sinistrally or planispirally coiled teleoconchs....
- Superfamily ScissurelloideaScissurelloideaScissurelloidea is a superfamily of minute sea snails, marine gastropod mollusks or micromollusks in the clade Vetigastropoda.-Taxonomy :This superfamily consists of two following families :*Family Scissurellidae Gray, 1847*Family Anatomidae McLean, 1989Geiger updated two other subfamilias to family...
- Superfamily SeguenzioideaSeguenzioideaSeguenzioidea is a superfamily of minute to medium-sized sea snails, marine gastropod mollusks in the clade Vetigastropoda. - 2007-2009 taxonomy :Kano et al...
Verrill, 1884 - Superfamily TrochoideaTrochoidea (superfamily)Trochoidea is a superfamily of small to very large vetigastropod sea snails with gills and an operculum.They have nacre as the inner shell layer...
Rafinesque, 1815 - top snails - Superfamily TurbinoideaTurbinoideaTurbinoidea is a superfamily of small to large sea snails, marine gastropod mollusks in the clade Vetigastropoda . But it is an available name, because it is not used in current taxonomy of gastropods sensu Williams et al...
- turban snails
External links
- Daniel L. Geiger and Christine E. Thacker, Molecular phylogeny of Vetigastropoda reveals non-monophyletic Scissurellidae, Trochoidea, and Fissurelloidea; Molluscan Research 25(1): 47–55 , ISSN 1323-5818
- Vetigastropoda taxonomy at NCBI
- Gastropod taxonomy at Paleos
- Gastropod reproductive behavior
- Gastropod Neuroscience
- Reconstructions of fossil gastropods
- 2004 Linnean taxonomy of gastropods