Gastropoda
. The larval shell of a gastropod is called a
protoconch.Most members have a
shell, which is in one piece and typically coiled or spiralled that usually opens on the right hand side (as viewed with the shell
apex pointing upward). Several species have an
operculum that operates as a trapdoor to close the shell. This is usually made of a horny material, but in some molluscs it is calcareous. In some members, the slugs, the shell is reduced or absent, and the body is streamlined so its torsion is relatively inconspicuous.
While the best-known gastropods are terrestrial, more than two thirds of all species live in a marine environment. Marine gastropods include
herbivores,
detritus feeders,
carnivores and a few ciliary feeders, in which the
radula is reduced or absent. The radula is usually adapted to the food that a species eats. The simplest gastropods are the
limpets and
abalones, both herbivores that use their hard radulas to rasp at
seaweeds on rocks. Many marine gastropods are burrowers and have siphons or tubes that extend from the
mantle and sometimes the shell. These act as snorkels, enabling the animal to continue to draw in a water current containing
oxygen and food into their bodies. The siphons are also used to detect prey from a distance. These gastropods breathe with
gills, but some freshwater species and almost all terrestric species have developed
lungs. While the gastropods with lungs all belong to one group (Pulmonata), the gastropods with gills are
paraphyletic.
Sea slugs are often flamboyantly coloured, either as a warning if they are poisonous or to
camouflage them on the
corals and seaweeds on which many of the species are found. Their gills are often in a form of feathery plumes on their backs which gives rise to their other name,
nudibranchs. Nudibranchs with smooth or warty backs have no visible gill mechanisms and respiration may take place directly through the skin. A few of the sea slugs are herbivores and some are carnivores. Many have distinct dietary preferences and regularly occur in association with certain species.
The first gastropods were exclusively marine, with the earliest representatives of the group appearing in the
Late Cambrian (
Chippewaella,
Strepsodiscus). Early
Cambrian forms like
Helcionella and
Scenella are no longer considered gastropods, and the tiny coiled
Aldanella of earliest Cambrian time is probably not even a mollusc. By the
Ordovician period the gastropods were a varied group present in a range of aquatic habitats. Commonly,
fossil gastropods from the rocks of the early
Palaeozoic era are too poorly preserved for accurate identification. Still, the
Silurian genus
Poleumita contains fifteen identified species. Fossil gastropods are less common during the Palaeozoic era than
bivalves.
Most of the gastropods of the Palaeozoic era belong to primitive groups, a few of which still survive today. By the
Carboniferous period many of the shapes we see in living gastropods can be matched in the fossil record, but despite these similarities in appearance the majority of these older forms are not directly related to living forms. It was during the
Mesozoic era that the ancestors of many of the living gastropods evolved.
One of the earliest known terrestrial (land-dwelling) gastropods is
Maturipupa which is found in the
Coal Measures of the Carboniferous period in
Europe, but relatives of the modern land snails are rare before the
Cretaceous period when the familiar
Helix first appeared.
In rocks of the Mesozoic era gastropods are slightly more common as fossils, their shell often well preserved. Their fossils occur in beds which were deposited in both freshwater and marine environments. The "Purbeck Marble" of the
Jurassic period and the "Sussex Marble" of the early Cretaceous period which both occur in southern
England are
limestones containing the tightly packed remains of the pond snail
Viviparus.
Rocks of the
Cenozoic era yield very large numbers of gastropod fossils, many of these fossils being closely related to modern living forms. The diversity of the gastropods increased markedly at the beginning of this era, along with that of the bivalves.
Certain trail-like markings preserved in ancient sedimentary rocks are thought to have been made by gastropods crawling over the soft mud and sand. Although these trails are of debatable origin, some of them do resemble the trails made by living gastropods today.
Gastropod fossils may sometimes be confused with
ammonites or other shelled
cephalopods. An example of this is
Bellerophon from the limestones of the
Carboniferous period in Europe which may be mistaken for a cephalopod.
Gastropods are one of the groups that record the changes in fauna caused by the advance and retreat of the Ice Sheets during the
Pleistocene epoch.
The
taxonomy of the Gastropoda is under constant revision, but more and more of the old taxonomy is being abandoned. Nevertheless terms as "opisthobranch" and "prosobranch" are still being used in a descriptive way. In a sense, we can speak of a taxonomic jungle when we go down to the lower taxonomic levels. The taxonomy of the Gastropoda can be different from author to author. But with the arrival of DNA-sequencing, further revisions of the higher taxonomic levels are to be expected in the near future.
According to the traditional classification there are four subclasses. :
*
Prosobranchia (gills in front of the heart).
*
Opisthobranchia (gills to the right and behind the heart).
*
Gymnomorpha (no shell)
*
Pulmonata (with lungs instead of gills)
According to the newest insights (Ponder & Lindberg, 1997), the taxonomy of the Gastropoda should be rewritten in terms of strictly
monophyletic groups. Integrating these findings into a working
taxonomy will be a true challenge in the coming years. At present, it is impossible to give a classification of the Gastropoda that has consistent ranks and also reflects current usage.
Class Gastropoda (
Cuvier, 1797)
Incertæ sedis*Order
Bellerophontida (
fossil)
*Order Mimospirina (
fossil)
Subclass Eogastropoda (
Ponder & Lindberg, 1996) (earlier:
Prosobranchia)
*Order Euomphalida de Koninck 1881 (
fossil)
***Superfamily Macluritoidea
***Superfamily Euomphaloidea
***Superfamily Platyceratoidea
*Order Patellogastropoda Lindberg,1986 (true limpets)
**Suborder Patellina Van Ihering,1876
***Superfamily Patelloidea
Rafinesque, 1815
**Suborder Nacellina Lindberg, 1988
***Superfamily Acmaeoidea Carpenter, 1857
***Superfamily Nacelloidea
Thiele, 1891
**Suborder Lepetopsina McLean, 1990
***Superfamily Lepetopsoidea McLean, 1990
Subclass Orthogastropoda Ponder & Lindberg, 1996 (earlier
Prosobranchia,
Opisthobranchia)
Incertæ sedis*Order Murchisoniina Cox & Knight, 1960 (
fossil)
*** Superfamily Murchisonioidea Koken, 1889
*** Superfamily Loxonematoidea Koken, 1889
*** Superfamily Lophospiroidea Wenz, 1938
*** Superfamily Straparollinoidea
** Grade Subulitoidea Lindström, 1884Superorder
Cocculiniformia Haszprunar, 1987
***Superfamily Cocculinoidea
Dall, 1882
***Superfamily Lepetelloidea
Dall, 1882 (deep sea limpets)Superorder ‘Hot Vent Taxa' Ponder & Lindberg, 1997
*Order Neomphaloida Sitnikova & Starobogatov, 1983
***Superfamily Neomphaloidea McLean, 1981 (hydrothermal vents limpets)
***Superfamily Peltospiroidea McLean, 1989Superorder
Vetigastropoda Salvini-Plawen, 1989 (limpets)
***Superfamily Fissurelloidea Flemming, 1822 (keyhole limpets)
***Superfamily Haliotoidea
Rafinesque, 1815 (abalones)
***Superfamily Lepetodriloidea McLean, 1988 (hydrothermal vent limpets)
***Superfamily Pleurotomarioidea Swainson, 1840 (slit shells)
***Superfamily Seguenzioidea Verrill, 1884
***Superfamily Trochoidea
Rafinesque, 1815 (top shells)Superorder
Neritaemorphi Koken, 1896
*Order Cyrtoneritomorpha (
fossil)
*Order Neritopsina Cox & Knight, 1960
***Superfamily Neritoidea
Lamarck, 1809Superorder
Caenogastropoda Cox, 1960
*Order
Architaenioglossa Haller, 1890
***Superfamily Ampullarioidea
J.E. Gray, 1824
***Superfamily Cyclophoroidea
J.E. Gray, 1847 (terrestrials)
*Order
Sorbeoconcha Ponder & Lindberg, 1997
**Suborder
Discopoda P. Fischer, 1884
***Superfamily Campaniloidea Douvillé, 1904
***Superfamily Cerithioidea Férussac, 1822
**Suborder
Hypsogastropoda Ponder & Lindberg, 1997
**Infraorder
Littorinimorpha Golikov & Starobogatov, 1975
***Superfamily Calyptraeoidea
Lamarck, 1809
***Superfamily Capuloidea J. Fleming, 1822
***Superfamily Carinarioidea Blainville, 1818 (formerly called Heteropoda)
***Superfamily Cingulopsoidea Fretter & Patil, 1958
***Superfamily Cypraeoidea
Rafinesque, 1815 (cowries)
***Superfamily Ficoidea Meek, 1864
***Superfamily Laubierinoidea Warén & Bouchet, 1990
***Superfamily Littorinoidea (Children), 1834 (periwinkles)
***Superfamily Naticoidea Forbes, 1838 (moon shells)
***Superfamily
Rissooidea J.E. Gray, 1847 (Risso shells) (includes genus oncomelania, schistosomiasis transmission vector)
***Superfamily Stromboidea
Rafinesque, 1815 (true conchs)
***Superfamily Tonnoidea Suter, 1913
***Superfamily Trivioidea Troschel, 1863
***Superfamily Vanikoroidea
J.E. Gray, 1840
***Superfamily Velutinoidea
J.E. Gray, 1840
***Superfamily Vermetoidea
Rafinesque, 1815 (worm shells)
***Superfamily Xenophoroidea Troschel, 1852 (carrier shells)
**Infraorder Ptenoglossa J.E. Gray, 1853
***Superfamily Eulimoidea Philippi, 1853
***Superfamily Janthinoidea
Lamarck, 1812
***Superfamily Triphoroidea
J.E. Gray, 1847
**Infraorder
Neogastropoda Thiele, 1929
***Superfamily
Buccinoidea (whelks, false tritions)
***Superfamily
Cancellarioidea Forbes & Hanley, 1851
***Superfamily
Conoidea Rafinesque, 1815
***Superfamily
Muricoidea Rafinesque, 1815Superorder Heterobranchia
J.E. Gray, 1840
*Order Heterostropha P. Fischer, 1885
***Superfamily Architectonicoidea
J.E. Gray, 1840
***Superfamily Nerineoidea
Zittel, 1873 (
fossil)
***Superfamily Omalogyroidea
G.O. Sars, 1878
***Superfamily Pyramidelloidea
J.E. Gray, 1840
***Superfamily Rissoelloidea
J.E. Gray, 1850
***Superfamily Valvatoidea
J.E. Gray, 1840
*Order Opisthobranchia
Milne-Edwards, 1848
**Suborder
Cephalaspidea P. Fischer, 1883
***Superfamily
Acteonoidea D'Orbigny, 1835
***Superfamily
Bulloidea Lamarck, 1801
***Superfamily
Cylindrobulloidea Thiele, 1931 (has to be included in the Sacoglossa)
***Superfamily
Diaphanoidea Odhner, 1914
***Superfamily
Haminoeoidea Pilsbry, 1895
***Superfamily
Philinoidea J.E. Gray, 1850
***Superfamily
Ringiculoidea Philippi, 1853
**Suborder
Sacoglossa Von Ihering, 1876
***Superfamily Oxynooidea H. & A. Adams, 1854
**Suborder
Anaspidea P. Fischer, 1883 (sea hares)
***Superfamily
Akeroidea Pilsbry, 1893
***Superfamily
Aplysioidea Lamarck, 1809
**Suborder Notaspidea P. Fischer, 1883
***Superfamily Tylodinoidea
J.E. Gray, 1847
***Superfamily Pleurobranchoidea Férussac, 1822
**Suborder
Thecosomata Blainville, 1824 (sea butterflies)
***Infraorder Euthecosomata
****Superfamily
Limacinoidea****Superfamily
Cavolinioidea***Infraorder
Pseudothecosomata****Superfamily Peraclidoidea
****Superfamily Cymbulioidea
**Suborder
Gymnosomata Blainville, 1824 (sea angels)
***Family
Clionidae Rafinesque, 1815
***Family
Cliopsidae Costa, 1873
***Family
Hydromylidae Pruvot-Fol, 1942
***Family
Laginiopsidae Pruvot-Fol, 1922
***Family
Notobranchaeidae Pelseneer, 1886
***Family
Pneumodermatidae Latreille, 1825
***Family
Thliptodontidae Kwietniewski, 1910
|
Clausiliidae or Door Snails |
**Suborder Nudibranchia Blainville, 1814 (nudibranchs)
**Infraorder Anthobranchia Férussac, 1819
***Superfamily Doridoidea
Rafinesque, 1815
***Superfamily Doridoxoidea Bergh, 1900
***Superfamily Onchidoridoidea Alder & Hancock, 1845
***Superfamily Polyceroidea Alder & Hancock, 1845
**Infraorder Cladobranchia Willan & Morton, 1984
***Superfamily Dendronotoidea Allman, 1845
***Superfamily Arminoidea
Rafinesque, 1814
***Superfamily Metarminoidea Odhner in Franc, 1968
***Superfamily Aeolidioidea
J.E. Gray, 1827
*Order
Pulmonata Cuvier in Blainville, 1814 (pulmonates)
**Suborder
Systellommatophora Pilsbry, 1948
***Superfamily Onchidioidea
Rafinesque, 1815
***Superfamily Otinoidea H. & A. Adams, 1855
***Superfamily Rathouisioidea Sarasin, 1889
**Suborder
Basommatophora Keferstein in Bronn, 1864 (freshwater pulmonates, pond snails)
***Superfamily
Acroloxoidea Thiele, 1931
***Superfamily
Amphiboloidea J.E. Gray, 1840
***Superfamily
Chilinoidea H. & A. Adams, 1855
***Superfamily
Glacidorboidea Ponder, 1986
***Superfamily
Lymnaeoidea Rafinesque, 1815
***Superfamily
Planorboidea Rafinesque, 1815
***Superfamily
Siphonarioidea J.E. Gray, 1840
**Suborder
Eupulmonata Haszprunar & Huber, 1990
**Infraorder Acteophila
Dall, 1885 (= formerly Archaeopulmonata)
***Superfamily Melampoidea Stimpson, 1851
**Infraorder Trimusculiformes Minichev & Starobogatov, 1975
***Superfamily Trimusculoidea Zilch, 1959
**Infraorder Stylommatophora A. Schmidt, 1856 (land snails)
**Subinfraorder Orthurethra
***Superfamily Achatinelloidea Gulick, 1873
***Superfamily Cochlicopoidea Pilsbry, 1900
***Superfamily Partuloidea Pilsbry, 1900
***Superfamily Pupilloidea Turton, 1831
**Subinfraorder Sigmurethra
***Superfamily Acavoidea Pilsbry, 1895
***Superfamily Achatinoidea Swainson, 1840
***Superfamily Aillyoidea Baker, 1960
***Superfamily Arionoidea
J.E. Gray in Turnton, 1840
***Superfamily
Buliminoidea Clessin, 1879
***Superfamily Camaenoidea Pilsbry, 1895
***Superfamily Clausilioidea Mörch, 1864
***Superfamily Dyakioidea Gude & Woodward, 1921
***Superfamily Gastrodontoidea Tryon, 1866
***Superfamily
Helicoidea Rafinesque, 1815
***Superfamily Helixarionoidea Bourguignat, 1877
***Superfamily
Limacoidea Rafinesque, 1815
***Superfamily Oleacinoidea H. & A. Adams, 1855
***Superfamily Orthalicoidea Albers-Martens, 1860
***Superfamily Plectopylidoidea Moellendorf, 1900
***Superfamily Polygyroidea Pilsbry, 1894
***Superfamily Punctoidea Morse, 1864
***Superfamily Rhytidoidea Pilsbry, 1893
***Superfamily Sagdidoidera Pilsbry, 1895
***Superfamily Staffordioidea
Thiele, 1931
***Superfamily Streptaxoidea
J.E. Gray, 1806
***Superfamily Strophocheiloidea
Thiele, 1926
***Superfamily Trigonochlamydoidea Hese, 1882
***Superfamily Zonitoidea Mörch, 1864
***? Superfamily Athoracophoroidea P. Fischer, 1883 (= Tracheopulmonata)
***? Superfamily Succineoidea Beck, 1837 (= Heterurethra)Other extant classes of the Mollusca are
Bivalvia,
Scaphopoda,
Aplacophora,
Polyplacophora,
Monoplacophora and
Cephalopoda.
*Paul Jeffery.
Suprageneric classification of class GASTROPODA. The Natural History Museum, London, 2001
*Ponder & Lindberg,
Towards a phylogeny of gastropod molluscs; an analysis using morphological characters.
Zoological Journal of the Linnean Society,
119 83-2651; 1997
*
Taxonomy*
Gastropod Classification compiled by Paul Jeffery*
International Code of Zoological Nomenclature 4th edition, 2000*
Gastropods in captivity
