Molluscivore

A molluscivore is a carnivorous animal that specialises in feeding on molluscs such as gastropods, bivalves, brachiopods and cephalopods. Known molluscivores include numerous predatory (and often cannibalistic) molluscs, (e.g.octopuses, murexes, decollate snails and oyster drills), arthropods such as crabs and firefly larvae, and, vertebrates such as fish, birds and mammals.[1] Molluscivory is performed in a variety ways with some animals highly adapted to this method of feeding behaviour. A similar behaviour, durophagy, describes the feeding of animals that consume hard-shelled or exoskeleton bearing organisms, such as corals, shelled molluscs, or crabs.[2]

Description

Molluscivory is performed in several ways.

In some cases, the mollusc prey are simply swallowed entire, including the shell, whereupon the prey is killed through suffocation and or exposure to digestive enzymes. Only cannibalistic sea slugs, snail-eating cone shells of the taxon Coninae, and some sea anemones use this method.

One method, used especially by vertebrate molluscivores, is to break the shell, either by exerting force on the shell until it breaks, often by biting the shell, like with oyster crackers, mosasaurs, and placodonts, or hammering at the shell, e.g. oystercatchers and crabs, or by simply dashing the mollusc on a rock (e.g. song thrushes, gulls, and sea otters).

Lampyris noctiluca (larva eating)
A common glowworm larva hunting snails

Another method is to remove the shell from the prey. Molluscs are attached to their shell by strong muscular ligaments, making the shell's removal difficult. Molluscivorous birds, such as oystercatchers and the Everglades snail kite, insert their elongate beak into the shell to sever these attachment ligaments, facilitating removal of the prey. The carnivorous terrestrial pulmonate snail known as the "decollate snail" ("decollate" being a synonym for "decapitate") uses a similar method: it reaches into the opening of the prey's shell and bites through the muscles in the prey's neck, whereupon it immediately begins devouring the fleshy parts of its victim. The walrus sucks meat out of bivalve molluscs by sealing its powerful lips to the organism and withdrawing its piston-like tongue rapidly into its mouth, creating a vacuum.

Another method is used by many molluscs, themselves. Octopi, nautilii, and most molluscivoruous sea snails use their radula to drill a hole through the shell, then inject venom and digestive enzymes through the hole, whereupon the digested prey is then sucked out through the hole.

The larvae of glowworms and fireflies are simply small enough to enter the shells of terrestrial snails and begin eating immediately.

In marine mammals

Walrus - Kamogawa Seaworld - 1
The walrus, an aquatic molluscivore

Whales: Sperm whales, pilot whales, Cuvier's beaked whale, Risso's dolphin and species in the genera Mesoplodon, and Hyperoodon and the superfamily Physeteroidea are classified as molluscivores, eating mainly squid.[3]

Pinnipeds: Elephant seals, Ross seals and South American fur seals are classed as molluscivores.[3] The walrus eats benthic bivalve molluscs, especially clams, for which it forages by grazing along the sea bottom, searching and identifying prey with its sensitive vibrissae.[4] The walrus sucks the meat out by sealing its powerful lips to the organism and withdrawing its piston-like tongue rapidly into its mouth, creating a vacuum. The walrus palate is uniquely vaulted, enabling effective suction.

In fish

Several species of pufferfish and loaches are molluscivores. As many molluscs are protected by a shell, the feeding techniques applied amongst molluscivore fish are highly specialized and usually divided into two groups: "crushers" and "slurpers." Pufferfish tend to be crushers and will use their beak-like teeth to break the shell in order to gain access to the meat inside. Loaches are specialized slurpers, and will make use of their characteristically shaped snout in order to grab hold of, then suck out the animal living inside the shell.

Spotted Pufferfish Arothron meleagris 02
The spotted pufferfish, a molluscivore

The black carp (Mylopharyngodon piceus) commonly feeds by crushing large molluscs with pharyngeal teeth, extracting soft tissue, and spitting out shell fragments. Four-year-old juveniles are capable of consuming approximately 1–2 kg of molluscs per day. This bottom-dwelling molluscivore was purposely imported into the United States in the early 1970s for use as a food fish and also as a biological control agent for snails—an intermediate host for a trematode parasite in fish reared on fish farms.[5] Two snail-eating cichlids, Trematocranus placodon and Maravichromis anaphyrmis, have been tried as biological control agents of schistosomes in fish ponds in Africa.[6] Redear sunfish (Lepomis micropholus) and bluegill (Lepomis macrochirus) have been used to control quagga mussels (Dreissena bugensis) in the lower Colorado River in the US.[7]

The common name of some fish reflects their molluscivorous feeding, for example, the "snail-crusher hap" (Trematocranus placodon), ""red rock sheller" (Haplochromis sp.), "Rusinga oral sheller" (Haplochromis sp.) and "rainbow sheller" (Haplochromis sp.). The redear sunfish is also known as the "shellcracker".

In reptiles

Gray's monitor (or "butaan") is well known for its diet, which consists primarily of ripe fruit; however, several prey items are also consumed, including snails. [8] Monitors are generally carnivorous animals, which makes the Gray's monitor somewhat of an exception amongst the varanid family.

The prehistoric placodont reptiles is an extinct taxon of marine animals that superficially resembled lizards and turtles, most of whose dentition of peg-like incisors and enormous, molar-like teeth allowed them to prey on molluscs and brachiopods by plucking their prey off of the substrate, and crushing the shells.[9][10]

In birds

Among birds, the eponymous shorebirds known as oystercatchers are renowned for feeding upon bivalves. At least one bird of prey is also primarily a molluscivore—the snail kite, Rostrhamus sociabilis. The limpkin is a small rail-like bird that feeds almost entirely on apple snails. Other birds that will eat molluscs occasionally include mergansers, ducks, coots, dippers and spoonbills.[11]

In invertebrates

Conus marmoreus feeding on cowrie
Cone snail feeding on a cowrie
Cone shell venom apparatus
Venom apparatus of a cone snail

Cone snails: Some cone snails hunt and eat other kinds of snails, such as cowries, olive shells, turbo snails, and conch snails, while others will eat other cone snails. Conus marmoreus and Conus omaria are able to kill and swallow prey that are larger than themselves; some Conus species can swallow prey that weigh up to half of their own weight. Snail's bodies are attached to their shell by a columellar muscle that holds onto the columella, the axis of the snail. This muscle also allows the snail to retract back into its shell. If this muscle is broken, the snail will lose its shell and die. It is hard to detach this muscle in a live snail, or even in a dead snail. It is thought that the conotoxins in the venom of cone snails are able to completely relax this muscle so that the body can be pulled out from its shell. The cone snail uses its foot to hold the shell of its prey. Using a strong, steady pulling motion, the body of the snail can be forced out and then swallowed whole. Complete digestion of a snail can take many hours, even days.[12]

Starfish: Primitive starfish, such as Astropecten and Luidia, swallow their prey whole and start to digest it in their cardiac stomachs. Shell valves and other inedible materials are ejected through their mouths. The semi-digested fluid is passed into their pyloric stomachs and caeca where digestion continues and absorption occurs.[13] The margined sea star (Astropecten articulatus) is a well known molluscivore. It catches prey with its arms which it then takes to the mouth. The prey is then trapped by the long, moving prickles around the mouth cavity and swallowed food.

In more advanced species of starfish, the cardiac stomach can be everted from the organism's body to engulf and digest food. When the prey is a clam, the starfish pulls with its tube feet to separate the two valves slightly, and inserts a small section of its stomach, which releases enzymes to digest the prey. The stomach and the partially digested prey are later retracted into the disc. Here the food is passed on to the pyloric stomach, which always remains inside the disc.[14] Because of this ability to digest food outside the body, starfish can hunt prey much larger than their mouths.

Crabs: The freshwater crabs Syntripsa matannensis and Syntripsa flavichela are classed as molluscivores.[15] Using their massive and powerful claws, adult Florida stone crabs (Menippe mercenaria) feed on acorn barnacles, hard-shelled clams, scallops, and conch.[16]

References

  1. ^ "Molluscivore". Palaeos. Retrieved June 5, 2013.
  2. ^ Huber, D.R., Dean, M.N. and Summers, A.P., (2008), Hard prey, soft jaws and the ontogeny of feeding mechanics in the spotted ratfish Hydrolagus colliei. Journal of the Royal Society Interface( online publishing) [1]
  3. ^ a b Jarman, P.J, Lww, A.K. and Hall, L.S. "Fauna of Australia:Natural History of the Eutheria" (PDF). Archived from the original (PDF) on 2012-03-21. Retrieved June 8, 2013.CS1 maint: Multiple names: authors list (link)
  4. ^ Levermann, N., Galatius, A., Ehlme, G., Rysgaard, S. and Born, E.W. (2003). "Feeding behaviour of free-ranging walruses with notes on apparent dextrality of flipper use". BMC Ecology. 3 (9): 9. doi:10.1186/1472-6785-3-9. PMC 270045. PMID 14572316.CS1 maint: Multiple names: authors list (link)
  5. ^ Crosier, D.M., Molloy, D.P. and Rasmussen, J. "Black Carp Mylopharyngodon piceus" (PDF). Archived from the original (PDF) on 2013-02-17. Retrieved June 8, 2013.CS1 maint: Multiple names: authors list (link)
  6. ^ Chiotha, S.S., McKaye, K.R, Stauffer, J.R., (1991). Use of indigenous fishes to control schistosome snail vectors in Malaŵi, Africa. Biological Control, 1: 316–319
  7. ^ Karp, K. "Summary of Laboratory Experiments to Evaluate Consumption of Juvenile/Adult Quagga Mussel by Redear Sunfish and Bluegill". Retrieved June 8, 2013.
  8. ^ "The Butaan Project - Background and History". Retrieved June 8, 2013.
  9. ^ Rieppel, O. (2002). Feeding mechanisms in Triassic stem-group sauropterygians: the anatomy of a successful invasion of Mesozoic seas Zoological Journal of the Linnean Society, 135, 33-63
  10. ^ Naish, D. 2004. Fossils explained 48. Placodonts. Geology Today 20 (4), 153-158.
  11. ^ Mayntz, M. "Molluscivorous". Retrieved June 7, 2013.
  12. ^ Chadwick, A. (2013). "The cone snail". Retrieved June 7, 2013.
  13. ^ Ruppert, E.E., Fox, R.S. and Barnes, R.D., (2004). Invertebrate Zoology, 7th edition. Cengage Learning. ISBN 81-315-0104-3
  14. ^ Dale, Jonathan (2000). "Starfish Digestion and Circulation". Madreporite Nexus. Retrieved June 7, 2013.
  15. ^ Schubart, C.D., Santl, T. and Koller, P., (2008). Mitochondrial patterns of intra- and interspecific differentiation among endemic freshwater crabs of ancient lakes in Sulawesi. Contributions to Zoology, 77: 83-90 [2]
  16. ^ Williams, A., (1984). Shrimps, lobsters, and crabs of the Atlantic coast of the Eastern United States, Maine to Florida. Washington, D. C.: Smithsonian Institution.
Aivukus

Aivukus is an extinct genus of walrus from the Miocene.

Avivore

An avivore is a specialized predator of birds, with birds making up a large proportion of its diet. Such bird-eating animals come from a range of groups.

Bacterivore

Bacterivores are free-living, generally heterotrophic organisms, exclusively microscopic, which obtain energy and nutrients primarily or entirely from the consumption of bacteria. Many species of amoeba are bacterivores, as well as other types of protozoans. Commonly, all species of bacteria will be prey, but spores of some species, such as Clostridium perfringens, will never be prey, because of their cellular attributes.

Bottom feeder

A bottom feeder is an aquatic animal that feeds on or near the bottom of a body of water. The body of water could be the ocean, a lake, a river, or an aquarium. Bottom feeder is a term used particularly with aquariums. Biologists often use the terms benthos — particularly for invertebrates such as shellfish, crabs, crayfish, sea anemones, starfish, snails, bristleworms and sea cucumbers — and benthivore or benthivorous, for fish and invertebrates that feed on material from the bottom. However the term benthos includes all aquatic life that lives on or near the bottom, which means it also includes non-animals, such as plants and algae.

Biologists also use specific terms that refer to bottom feeding fish, such as demersal fish, groundfish, benthic fish and benthopelagic fish. Examples of bottom feeding fish species groups are flatfish (halibut, flounder, plaice, sole), eels, cod, haddock, bass, grouper, carp, bream (snapper) and some species of catfish and shark.

Carnivorous fungus

Carnivorous fungi or predaceous fungi are fungi that derive some or most of their nutrients from trapping and eating microscopic or other minute animals. More than 200 species have been described, belonging to the phyla Ascomycota, Mucoromycotina, and Basidiomycota. They usually live in soil and many species trap or stun nematodes (nematophagous fungus), while others attack amoebae or collembola.

Fungi that grow on the epidermis, hair, skin, nails, scales or feathers of living or dead animals are considered to be dermatophytes rather than carnivores. Similarly fungi in orifices and the digestive tract of animals are not carnivorous, and neither are internal pathogens. Neither are insect pathogens that stun and colonize insects normally labelled carnivorous if the fungal thallus is mainly in the insect as does Cordyceps, or if it clings to the insect like the Laboulbeniales.

Two basic trapping mechanisms have been observed in carnivorous fungi that are predatory on nematodes:

constricting rings (active traps)

adhesive structures (passive traps)Sequencing of ribosomal DNA has shown that these trap types occur in separate fungus lineages, an example of convergent evolution.

Consumer–resource interactions

Consumer–resource interactions are the core motif of ecological food chains or food webs, and are an umbrella term for a variety of more specialized types of biological species interactions including prey-predator (see predation), host-parasite (see parasitism), plant-herbivore and victim-exploiter systems. These kinds of interactions have been studied and modeled by population ecologists for nearly a century. Species at the bottom of the food chain, such as algae and other autotrophs, consume non-biological resources, such as minerals and nutrients of various kinds, and they derive their energy from light (photons) or chemical sources. Species higher up in the food chain survive by consuming other species and can be classified by what they eat and how they obtain or find their food.

Decomposer

Decomposers are organisms that break down dead or decaying organisms, and in doing so, they carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development. While the terms decomposer and detritivore are often interchangeably used, detritivores must ingest and digest dead matter via internal processes while decomposers can directly absorb nutrients through chemical and biological processes hence breaking down matter without ingesting it. Thus, invertebrates such as earthworms, woodlice, and sea cucumbers are technically detritivores, not decomposers, since they must ingest nutrients and are unable to absorb them externally.

Florivore

In zoology, a florivore (not to be confused with a folivore) is an animal which mainly eats products of flowers. Florivores are types of herbivores (often referred to as floral herbivores), yet within the feeding behaviour of florivory, there are a range of other more specific feeding behaviours, including, but not limited to:

Granivory: the consumption of grain and seeds

Nectarivory: the consumption of flower nectar

Palynivory: the consumption of flower pollen

Frugivory: the consumption of fruit

Folivore

In zoology, a folivore is a herbivore that specializes in eating leaves. Mature leaves contain a high proportion of hard-to-digest cellulose, less energy than other types of foods, and often toxic compounds. For this reason, folivorous animals tend to have long digestive tracts and slow metabolisms. Many enlist the help of symbiotic bacteria to release the nutrients in their diet. Additionally, as has been observed in folivorous primates, they exhibit a strong preference towards immature leaves, which tend to be easier to masticate, tend to be higher in energy and protein, and lower in fibre and poisons than more mature fibrous leaves.

Hypercarnivore

A hypercarnivore is an animal which has a diet that is more than 70% meat, with the balance consisting of non-animal foods such as fungi, fruits or other plant material. Some extant examples include crocodiles, alligators, owls, shrikes, eagles, vultures, felids, most wild canids, dolphins, orcas, snakes, spiders, scorpions, mantises, marlins, groupers, and most sharks. Every species in the Felidae family, including the domesticated cat, is a hypercarnivore in its natural state. Additionally, this term is also used in paleobiology to describe taxa of animals which have an increased slicing component of their dentition relative to the grinding component. Hypercarnivores per definition need not be apex predators. For example, salmon are exclusively carnivorous, yet they are prey at all stages of life for a variety of organisms.

Many prehistoric mammals of the clade Carnivoramorpha (Carnivora and Miacoidea without Creodonta), along with the early order Creodonta, and some mammals of the even earlier order Cimolesta, were hypercarnivores. The earliest carnivorous mammal is considered to be Cimolestes, which existed during the Late Cretaceous and early Paleogene periods in North America about 66 million years ago. Theropod dinosaurs such as Tyrannosaurus rex that existed during the late Cretaceous, although not mammals, were obligate carnivores.

Large hypercarnivores evolved frequently in the fossil record, often in response to an ecological opportunity afforded by the decline or extinction of previously dominant hypercarnivorous taxa. While the evolution of large size and carnivory may be favored at the individual level, it can lead to a macroevolutionary decline, wherein such extreme dietary specialization results in reduced population densities and a greater vulnerability for extinction. As a result of these opposing forces, the fossil record of carnivores is dominated by successive clades of hypercarnivores that diversify and decline, only to be replaced by new hypercarnivorous clades.

As an example of related species with differing diets, even though they diverged only 150,000 years ago, the polar bear is the most highly carnivorous bear (more than 90% of its diet is meat) while the grizzly bear is one of the least carnivorous in many locales, with less than 10% of its diet being meat.

List of feeding behaviours

Feeding is the process by which organisms, typically animals, obtain food. Terminology often uses either the suffixes -vore, -vory, -vorous from Latin vorare, meaning "to devour", or -phage, -phagy, -phagous from Greek φαγειν (phagein), meaning "to eat".

Mesocarnivore

A mesocarnivore is an animal whose diet consists of 30–70% meat with the balance consisting of non-vertebrate foods which may include fungi, fruits, and other plant material. Mesocarnivores are seen today among the Canidae (coyotes, foxes), Viverridae (civets), Mustelidae (martens, tayra), Procyonidae (ringtail, raccoon), Mephitidae (skunks), and Herpestidae (some mongooses).

Mucophagy

Mucophagy (literally "mucus feeding") is feeding on mucus of fishes or invertebrates. It may also refer to consumption of mucus or dried mucus in primates.

There are mucophagous parasites, such as some sea lice that attach themselves to gill segments of fish.Mucophages may serve as cleaners of other animals.

Another usage of this term is in reference to the feeding organ rich in mucous cells which pumps the water through, feeding particles get entrapped in mucus, and the latter proceeds into the esophagus.

Paedophagy

Paedophagy (literally meaning the "consumption of children") in its general form is the feeding behaviour of fish or other animals whose diet is partially, or primarily the eggs or larvae of other animals. However, P. H. Greenwood, who was the first to describe paedophagia, defines it to be a feeding behaviour evolved among cichlid fishes.

Planktivore

A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton.

Saprophagy

Saprophages are olophages that obtain nutrients by consuming decomposing dead plant or animal biomass. They are distinguished from detritivores in that saprophages are sessile consumers while detritivore are mobile. Typical saprophagic animals include sedentary polychaetes such as amphitrites (Amphitritinae, worms of the family Terebellidae) and other terebellids.

The eating of wood, whether live or dead, is known as xylophagy. Τhe activity of animals feeding only on dead wood is called sapro-xylophagy and those animals, sapro-xylophagous.

Syntripsa

Syntripsa is a genus of freshwater crabs found in lakes on the Indonesian island of Sulawesi.

Vermivore

Vermivore (from Latin vermi, meaning "worm" and vorare, "to devour") is a zoological term for animals that eat worms (including annelids, nematodes, and other worm-like animals). Animals with such a diet are known to be vermivorous. Some definitions are less exclusive with respect to the diet, but limit the definition to particular animals, e.g. "Feeding on worms or insect vermin. Used of a bird."An entire genus of New World warblers has been given the name Vermivora.

One vermivore that may feed exclusively on worms is Paucidentomys vermidax, a rodent species of a type commonly known as shrew rats which was discovered in 2011 in Indonesia. The name, which can be translated as "worm-eating, few-toothed mouse", refers to the fact that they have only four teeth and may live exclusively on a diet of earthworms. This reduced dentition in vermivorous mammals is said to be due to relaxed selectional pressure on dental occlusion.

Xylophagy

Xylophagy is a term used in ecology to describe the habits of an herbivorous animal whose diet consists primarily (often solely) of wood. The word derives from Greek ξυλοφάγος (xulophagos) "eating wood", from ξύλον (xulon) "wood" and φαγεῖν (phagein) "to eat", an ancient Greek name for a kind of a worm-eating bird. Animals feeding only on dead wood are called sapro-xylophagous or saproxylic.

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