Species
Mollusca
IUCN
NCBI
EOL Text
The phylum Mollusca contains some of the most familiar invertebrates, including snails, slugs, clams, mussels, and octopuses. In contrast to these well-known molluscs, however, others are almost never seen, such as the aplacophorans and monoplacophorans, the latter of which which were only known from Paleozoic fossils until the first live specimen was discovered in the deep sea in 1952 (UCMP 2008).
Except for the aplacophorans, most molluscs have a well-developed, muscular foot. This structure is used in a multitude of ways, for example: locomotion, clinging to surfaces, burrowing, anchoring in sediment, swimming, and grasping (modified into prehensile tentacles in octopuses). The vast diversity of foot adaptations exemplifies the huge morphological diversity of the mollusc form.
A layer of epidermal tissue called the mantle surrounds the body of molluscs. Specialized glands in the mantle are responsible for the extracellular excretions that form shell structures. In all molluscan groups the shell is produced in layers of (usually) calcium carbonate, either in calcite or aragonite form.
Molluscs have adapted to terrestrial, marine and freshwater habitats all over the globe, although most molluscs are marine. Nearly 100,000 mollusc species are known (excluding the large number of extinct species known only as fossils) and it is clear that many thousands of species of extant species remain undescribed. Around 80% of known molluscs are gastropods (snails and slugs).
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Rights holder/Author | Dana Campbell, Campbell, Dana, EOL Rapid Response Team |
Source | http://eolspecies.lifedesks.org/pages/15878 |
Mollusca is prey of:
mixed-food consumers
secondary carnivores
Callinectes
Actinopterygii
Alburnus alburnus
bleak
Geococcyx californianus
Pollicipes polymerus
Huso huso
Oncorhynchus tshawytscha
Pseudodoras niger
Lates niloticus
Lepomis megalotis
Coris aygula
Ambystoma annulatum
Caretta caretta
Thamnophis butleri
Diadophis punctatus
Gavia stellata
Diomedea epomophora
Sula dactylatra
Egretta thula
Egretta tricolor
Mycteria americana
Eudocimus ruber
Cygnus olor
Anas fulvigula
Anas strepera
Anas cyanoptera
Anas americana
Aix sponsa
Aythya americana
Pandion haliaetus
Coturnix delegorguei
Actitis macularia
Larus canus
Fratercula cirrhata
Anodorhynchus hyacinthinus
Passerella iliaca
Corvus caurinus
Sorex gaspensis
Neurotrichus gibbsii
Peromyscus gossypinus
Lagenorhynchus australis
Lagenorhynchus cruciger
Feresa attenuata
Phocoenoides dalli
Delphinapterus leucas
Monodon monoceros
Mesoplodon europaeus
Mesoplodon carlhubbsi
Mesoplodon layardii
Enhydra lutris
Zalophus californianus
Neophoca cinerea
Callorhinus ursinus
Arctocephalus australis
Arctocephalus philippii
Arctocephalus townsendi
Phoca largha
Monachus tropicalis
Mirounga leonina
Mirounga angustirostris
Cephalophus niger
Alligator mississippiensis
Puma concolor
Prionailurus viverrinus
Mesoplodon peruvianus
Coturnix adansonii
Eremophila alpestris
Euoticus elegantulus
Cebus olivaceus
Hydromys chrysogaster
Ambystoma mexicanum
Amblonyx cinereus
Lontra provocax
Lutrogale perspicillata
Melogale personata
Martes melampus
Arvicola terrestris
Solenodon paradoxus
Potamogale velox
Based on studies in:
unknown: Black Sea (Marine)
Mexico: Guerrero (Coastal)
Uganda (Lake or pond)
England, River Thames (River)
This list may not be complete but is based on published studies.
- T. S. Petipa, E. V. Pavlova, G. N. Mironov, The food web structure, utilization transport of energy by trophic levels in the planktonic communities. In: Marine Food Chains, J. H. Steele, Ed. (Oliver and Boyd, Edinburgh, 1970), 142-167, from p. 154.
- T. S. Petipa, E. V. Pavlova, G. N. Mironov, The food web structure, utilization transport of energy by trophic levels in the planktonic communities. In: Marine Food Chains, J. H. Steele, Ed. (Oliver and Boyd, Edinburgh, 1970), 142-167 from p. 155.
- A. Yanez-Arancibia, Taxonomia, ecologia y estructura de las comunidades de peces en lagunas costeras con bocas efimeras del Pacifico de Mexico.
- K. H. Mann, R. H. Britton, A. Kowalczewski, T. J. Lack, C. P. Mathews and I. McDonald, Productivity and energy flow at all trophic levels in the River Thames, England. In: Productivity Problems of Freshwaters, Z. Kajak and A. Hillbricht-Ilkowska, Eds. (P
- M. J. Burgis, I. G. Dunn, G. G. Ganf, L. M. McGowan and A. B. Viner, Lake George, Uganda: Studies on a tropical freshwater ecosystem. In: Productivity Problems of Freshwaters, Z. Kajak and A. Hillbricht-Ilkowska, Eds. (Polish Scientific, Warsaw, 1972), p
- K. H. Mann, Case history: The River Thames. In: River Ecology and Man (R. T. Oglesby, C. A. Carlson, J. A. McCann, Eds.), Academic Press, New York and London, pp. 215-232 (1972), from p. 224.
- Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed February 16, 2011 at http://animaldiversity.org. http://www.animaldiversity.org
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Rights holder/Author | Cynthia Sims Parr, Joel Sachs, SPIRE |
Source | http://spire.umbc.edu/fwc/ |
Mollusca preys on:
detritus
phytoplankton
saprophagous plankton
algae
zooplankton
seston
Based on studies in:
unknown: Black Sea (Marine)
Mexico: Guerrero (Coastal)
England, River Thames (River)
Uganda (Lake or pond)
This list may not be complete but is based on published studies.
- T. S. Petipa, E. V. Pavlova, G. N. Mironov, The food web structure, utilization transport of energy by trophic levels in the planktonic communities. In: Marine Food Chains, J. H. Steele, Ed. (Oliver and Boyd, Edinburgh, 1970), 142-167, from p. 154.
- T. S. Petipa, E. V. Pavlova, G. N. Mironov, The food web structure, utilization transport of energy by trophic levels in the planktonic communities. In: Marine Food Chains, J. H. Steele, Ed. (Oliver and Boyd, Edinburgh, 1970), 142-167 from p. 155.
- A. Yanez-Arancibia, Taxonomia, ecologia y estructura de las comunidades de peces en lagunas costeras con bocas efimeras del Pacifico de Mexico.
- K. H. Mann, R. H. Britton, A. Kowalczewski, T. J. Lack, C. P. Mathews and I. McDonald, Productivity and energy flow at all trophic levels in the River Thames, England. In: Productivity Problems of Freshwaters, Z. Kajak and A. Hillbricht-Ilkowska, Eds. (P
- M. J. Burgis, I. G. Dunn, G. G. Ganf, L. M. McGowan and A. B. Viner, Lake George, Uganda: Studies on a tropical freshwater ecosystem. In: Productivity Problems of Freshwaters, Z. Kajak and A. Hillbricht-Ilkowska, Eds. (Polish Scientific, Warsaw, 1972), p
- K. H. Mann, Case history: The River Thames. In: River Ecology and Man (R. T. Oglesby, C. A. Carlson, J. A. McCann, Eds.), Academic Press, New York and London, pp. 215-232 (1972), from p. 224.
License | http://creativecommons.org/licenses/by/3.0/ |
Rights holder/Author | Cynthia Sims Parr, Joel Sachs, SPIRE |
Source | http://spire.umbc.edu/fwc/ |
Like other systems, reproduction is highly variable among molluscs. Molluscs can be dioecious or simultaneously or sequentially hermaphroditic. Gametes are freely spawned in some groups, others have internal fertilization and complex mating behaviors, many produce egg capsules, egg cases, or brood chambers.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Campbell, Dana, Campbell, Dana, EOL Rapid Response Team |
Source | http://eolspecies.lifedesks.org/pages/15878 |
Most molluscs undergo spiral cleavage. Development can be direct (proceed right to settling into a juvenile form) or indirect, going through the swimming trochophore larval stage. The trochophore is very similar to the annelid trochophore. Before settling, many groups then go onto a second larval stage which is unique to molluscs: the feeding (usually) and swimming veliger larvae. Molluscs go through the uniquely molluscan process of torsion, usually during the veliger stage of development. Torsion involves counterclockwise rotation of the visceral mass up to 180 degrees with respect to the head and foot, to profoundly change the relative location of the body regions. Many groups then “detort” to some degree later in development or adulthood. Theories as to the evolutionary significance of torsion abound but this phenomenon is not well understood (Brusca and Brusca 2003). In the long run, torsion has allowed for much morphological diversification over the course of evolution.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Campbell, Dana, Campbell, Dana, EOL Rapid Response Team |
Source | http://eolspecies.lifedesks.org/pages/15878 |
The molluscs demonstrate remarkable morphological diversity, a characteristic that has confused molluscan taxonomy from the group’s inception. The Latin root molluscus means soft, and many soft-bodied invertebrates have been added and removed this group until Cuvier’s modern approximation in 1795 (Brusca and Brusca 2003). Mollusca is the second largest invertebrate phylum after the arthropods. Some 93,000 extant species have been described, but the thinking is this number represents only about half of the living species. 70,000 fossil species are also known. Most classifications recognize ten molluscan classes (two extinct). One class, the gastropods (snails and slugs), contains about 80% of mollusc species.
A very rich molluscan fossil record dates back 500 million year to the Precambrian. The evolutionary origins of molluscs are still disputed, but recent well-respected molecular phylogenetic analyses place the molluscs in the Lophotrochozoa, along with annelids, brachiopods, bryozoans and several other phyla (Halanych et al. 1995). Relationships within the Mollusca are also unclear and disputed; some recent analyses challenge whether this enormous phylum is a natural, monophyletic group (Sigwart and Sutton 2007 and references therein).
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Campbell, Dana, Campbell, Dana, EOL Rapid Response Team |
Source | http://eolspecies.lifedesks.org/pages/15878 |
Shell protects, supports, and allows for growth: shelled mollusks
The shells of many mollusks provide protection and support while accomodating growth due to their conical structure.
"Consider shapes that satisfy the following set of conditions. To provide both support and protection for the organism, the shape must be a hollow one, but an opening must exist somewhere. Growth can occur only by addition to the inner surface or the free edge. And the shape should change only minimally as it grows. A cubic shell with an open face won't work: addition to walls will give more shell relative to its contained volume, and addition to cylinder doesn't meet the conditions--addition to the edge will move it from short and fat to long and (relatively) thin. What will work are cones, whether circular or elliptical. Add to the edge and thicken the walls and one gets a bigger cone, isometric with the original.
With only slight variations of the condition of isometry, all sorts of wild derivatives of cones are possible--and these latter are the shapes in which shelled mollusks occur." (Vogel 2003:88-89)
Learn more about this functional adaptation.
- Steven Vogel. 2003. Comparative Biomechanics: Life's Physical World. Princeton: Princeton University Press. 580 p.
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Rights holder/Author | (c) 2008-2009 The Biomimicry Institute |
Source | http://www.asknature.org/strategy/540fc5992a4f793696fc0c9aa8cc78aa |
Protein plays role in crystal formation: molluscs
The conchiolin protein of many molluscs plays a role in shell formation by serving as a major matrix component for crystal formation.
"The shell is secreted by the mantle, the tissue layer under the shell, of the mollusc, and consists of two or three layers. The outermost is the periostracum, made of a tough protein called conchiolin. The periostracum is often brown in colour although it may be so thin that it is virtually transparent: sometimes it is quite furry…Inside the periostracum are one or two layers of argonite or calcite, different crystalline forms of calcium carbonate, more commonly known as chalk. The main central layer is called the prismatic layer: the inner layer is known as the lamellate or nacreous layer. Here the crystals are laid in an overlapping zigzag formation that scatters light and produces the iridescent effect known as 'mother of pearl.'" (Foy and Oxford Scientific Films 1982:115)
Learn more about this functional adaptation.
- Foy, Sally; Oxford Scientific Films. 1982. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London. 238 p.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | (c) 2008-2009 The Biomimicry Institute |
Source | http://www.asknature.org/strategy/3cd066ecf4fec0ba2514f1a836f55286 |
Barcode of Life Data Systems (BOLD) Stats
Specimen Records:111955
Specimens with Sequences:96802
Specimens with Barcodes:85733
Species:12390
Species With Barcodes:10815
Public Records:80414
Public Species:8847
Public BINs:12682