Transverse view of the buccal cavity with the radula

Radula types chart. Red=central tooth (rachis), Green=lateral teeth, Yellow=marginal teeth.

Radula is the scientific name for the toothed chitinous ribbon in the mouth of gastropods. They use it to graze and scrape diatoms and other microscopic algae off rock surfaces and other substrata. Image File history File links Size of this preview: 362 × 599 pixelsFull resolution (531 × 879 pixel, file size: 115 KB, MIME type: image/png) // third version of radula diagram. ... Image File history File links Size of this preview: 362 × 599 pixelsFull resolution (531 × 879 pixel, file size: 115 KB, MIME type: image/png) // third version of radula diagram. ... Image File history File links Size of this preview: 391 × 599 pixelsFull resolution (1335 × 2046 pixel, file size: 464 KB, MIME type: image/png) en:Image:Radula types. ... Image File history File links Size of this preview: 391 × 599 pixelsFull resolution (1335 × 2046 pixel, file size: 464 KB, MIME type: image/png) en:Image:Radula types. ... Structure of the chitin molecule, showing two of the N-Acetylglucosamine units that repeat to form long chains in beta-1,4 linkage. ... Subclass Subclass Eogastropoda     Patellogastropoda Subclass Orthogastropoda   Superorder Cocculiniformia   Superorder Hot Vent Taxa     Neomphaolida   Superorder Vetigastropoda   Superorder Neritaemorphi     Neritopsina   Superorder Caenogastropoda     Architaenioglossa     Sorbeoconcha   Superorder Heterobranchia     Heterostropha     Opisthobranchia     Pulmonata The gastropods, or univalves, are the largest and most successful class of mollusks, with 60,000-75,000 species, and second largest class... Orders Centrales Pennales Diatoms (Greek: (dia) = through + (temnein) = to cut, i. ... A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ...

The radula is common to all mollusks, except the bivalves, which feed by siphoning and filtering small particles from water. Classes Caudofoveata Aplacophora Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda † Rostroconchia The mollusks or molluscs are the large and diverse phylum Mollusca, which includes a variety of familiar creatures well-known for their decorative shells or as seafood. ... Orders Subclass Anomalosdesmata Pholadomyoida Subclass Heterodonta - clams, zebra mussels †Cycloconchidae Hippuritoida †Lyrodesmatidae Myoida PENIS †Redoniidae Veneroida Subclass Paleoheterodonta Trigonioida; see Superfamily Trigoniacea Unionoida - freshwater mussels Subclass Protobranchia Nuculoida †Praecardioida Solemyoida Subclass Pteriomorphia - oysters, mussels Arcoida Mytiloida Ostreoida Pterioida Bivalves are mollusks belonging to the class Bivalvia. ...

The mouth of the gastropods is located below the anterior part of the mollusk. It opens into a pocket-like buccal cavity, containing the radula sac.

The radula apparatus consists of two parts :

• the cartilaginous base (the odontophore), with the odontophore protractor muscle, the radula protractor muscle and the radula retractor muscle.
• the radula itself, with its longitudinal rows of chitinous and recurved teeth, the cuticula.

The odontophore is movable and protrusible and the radula itself is movable over the odontophore. Through this action the radula teeth are being erected. The tip of the odontophore then scrapes the surface, while the teeth cut and scoop up the food and convey the particles through the esophagus to the digestive tract. Structure of the chitin molecule, showing two of the N-Acetylglucosamine units that repeat to form long chains in beta-1,4 linkage. ... A smiling humans visible teeth. ... The esophagus (also spelled oesophagus/Å“sophagus, Greek ), or gullet is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. ...

These actions continually wear down the frontal teeth. New teeth are continuously formed at the posterior end of the buccal cavity in the radula sac. They are slowly brought forward to the tip by a slow forward movement of the ribbon, to be replaced in their turn when they are worn out. Teeth production is rapid (some species produce up to five rows per day). The number of teeth present depends on the species of mollusk and may number more than 100,000. Large numbers of teeth in a row (actually v-shaped on the ribbon in many species) is presumed to be a more primitive condition, but this may not always be true. The largest number of teeth per row is found in Pleurotomaria (gastropod) with over 200 teeth per row (Hyman, 1967). The shape and arrangement of teeth is an adaptation to the feeding regime of the species. In biology, a species is one of the basic units of biodiversity. ...

The teeth of the radula are lubricated by the mucus of the salivary gland, just above the radula. Food particles are trapped into this sticky mucus, smoothing the progress of food into the oesophagus. The salivary glands produce saliva, which keeps the mouth and other parts of the digestive system moist. ... Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). ...

Certain gastropods use their radula teeth to hunt other gastropods and bivalve mollusks, scraping away the soft parts for ingestion. Cone shells have a single radula tooth, that can be thrust like a harpoon into its prey, releasing a neurotoxin. A neurotoxin is a toxin that acts specifically on nerve cells – neurons – usually by interacting with membrane proteins and ion channels. ...

The number, shape, and specialized arrangement of teeth in each transverse row is consistent on a radula, and the different patterns can be used as a diagnostic characteristic to identify the species in many cases.

Each row of radula teeth consists of

• one central tooth (or rachis tooth)
• on each side : one or more lateral teeth
• and then : one or more marginal teeth.

This arrangement of the teeth is expressed in a teeth formula, with the following abbreviations :

• R : designates the central tooth or the rachis tooth (in case of lack of central tooth : the zero sign 0)
• the lateral teeth on each side are expressed by a specific number or D, in case the outer lateral tooth is dominant.
• the marginal teeth are designated by a specific number or, in case they are in a very large numbers, the infinity symbol ∞

docoglossan radula

This can be expressed in a typical formula such as: Image File history File links Size of this preview: 609 × 600 pixelsFull resolution (669 × 659 pixel, file size: 71 KB, MIME type: image/jpeg) Radula docoglosse dun archéogastéropode du genre patella vu sous loupe binoculaire. ... Image File history File links Size of this preview: 609 × 600 pixelsFull resolution (669 × 659 pixel, file size: 71 KB, MIME type: image/jpeg) Radula docoglosse dun archéogastéropode du genre patella vu sous loupe binoculaire. ...

3 + D + 2 + R + 2 + D + 3

meaning : on each side 3 marginal teeth, 1 dominant lateral tooth, 2 lateral teeth and one central tooth.

This results in 7 basic types :

• docoglossan or stereoglossan radula : in each row there is one usually small central tooth, flanked by 1-3 laterals (with the outer one dominant) and a few (3 at the most) hooked marginals. The central tooth may even be absent. This is the most primitive radula type, and we could assume it represents the plesiomorphic condition (i.e., the primitive character state, that is taken from an ancestor without change), such as would be possessed by the first mollusks (Eogastropoda, also Polyplacophora).
  • formula : 3 + D + 2 + R + 2 + D + 3
  • or : 3 + D + 2 + 0 + 2 + D + 3
• rhipidoglossan radula : a large central and symmetrical tooth, flanked on each side by several (usually five) lateral teeth and numerous closely packed flabellate marginals (typical examples : Vetigastropoda, Neritomorpha). This already marks an improvement over the simple docoglossan state.
  • formula : ∞ + 5 + R + 5 + ∞
  • In case of a dominant lateral tooth : ∞ + D + 4 + R + 4 + D + ∞

Radula (magn. 400x) of the Gray Garden Slug (Deroceras laeve) showing the chitinous ribbons with numerous inward-pointing denticles

• hystrichoglossan radula : each row with lamellate and hooked lateral teeth and hundreds of uniform marginal teeth that are tufted at their ends (typical example : Pleurotomariidae).
  • The radula formula of e.g. Pleurotomaria (Entemnotrochus) rumphii is  : ∞. 14. 27. 1. 27. 14. ∞
• taenioglossan radula : seven teeth in each row : one middle tooth, flanked on each side by one lateral and two marginal teeth (characteristic of the majority of Caenogastropoda).
  • formula : 2 + 1 + R + 1 + 2
• ptenoglossan radula : rows with no central tooth but a series of several uniform, pointed marginal teeth (typical example : Epitoniodea).
  • formula : n + 0 + n
• stenoglossan or rachiglossan radula : each row has one central tooth and one lateral tooth on each side (or no lateral teeth in some cases) (most Neogastropoda).
  • formula : 1 + R + 1
  • or : 0 + R + 0
• toxoglossan radula : The middle teeth are very small or lack completely. Each row has only two teeth of which only one is in use at a time. These grooved teeth are very long and pointed, with venom channels (neurotoxins) and barbs, and are not firmly fixed to the basal plate. The teeth can therefore be individually transferred to the proboscis and ejected like a harpoon into the prey (typical example : Conoidea).
  • formula : 1 + 0 + 1

These radula types show the evolution in the gastropods from herbivorous to carnivorous feeding patterns. Scraping algae requires many teeth, in accordance with the first three types. Carnivorous types need fewer teeth, especially laterals and marginals. The ptenoglossan radula is situated between the two extremes and is typical for gastropods, adapted to a life as parasites on polyps. Orders Docoglossa Eogastropoda is a subclass of the class Gastropoda, which includes the limpets. ... Lined Chiton (Tonicella lineata) Chitons, also called polyplacophorans and rarely polyplacophores, are 860 species of molluscs of the Class Polyplacophora. ... Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (1024 × 768 pixel, file size: 218 KB, MIME type: image/jpeg) Other versions no File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (1024 × 768 pixel, file size: 218 KB, MIME type: image/jpeg) Other versions no File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Caenogastropoda Categories: Animal stubs ... Superfamilies Buccinoidea Cancellarioidea Conoidea Muricoidea The Neogastropoda used to be an order of prosobranch gastropods in the taxonomy of Thiele (1921). ... Families Conidae Terebridae Turridae Conoidea is a superfamily within the gastropod suborder Hypsogastropoda. ... In zoology, a polyp is one of two forms of individuals found in many species of cnidarians. ...

In Fiction

Jabba The Hutt, a character from the Star Wars universe has a radula to help it digest food.[1] Jabba the Hutt is a fictional character in George Lucass science fiction saga Star Wars. ... Star Wars is an epic science fantasy saga and fictional universe created by George Lucas during the late 1970s. ...

See Also

• Hypostome

A hypostome (also called the maxilla, radula, labium or Unterkiefer), is a calcified harpoon-like structure near the mouth area of certain parasitic arthropods including ticks, that allows them to anchor themselves firmly in place on a host mammal while sucking blood. ...

References

• Molluscan buccal structures and radula
• A Comparison of the feeding behaviour and the functional morphology of radula structure in Nudibranchs
• Hickman Carole, S (1980). "Gastropod Radulae and the Assessment of Form in Evolutionary Paleontology". Paleobiology 6 (3): 276-294.