Editing Radula (section)

====Seven basic types====

* The '''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. The teeth are fixed in a stiff position on the radular ribbon. This is the most primitive radular 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 earliest mollusks ([[Eogastropoda]], also [[Polyplacophora]]; limpet families [[Patellidae]], [[Lottiidae]], [[Lepetidae]]).  The radula operates like a chain of 'shovels', and the rigid structure operates like a rasp, scraping at hardened macroalgae.<ref name="Steneck1982"/> Accordingly, docoglossan radulae are often hardened by biomineralization.<ref name="Steneck1982"/> Spaces between the teeth make the radula ill-suited to collecting microalgae.<ref name="Steneck1982"/>
** 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, called ''uncini'' (typical examples: [[Vetigastropoda]], [[Neritomorpha]]). This already marks an improvement over the simple docoglossan state.{{Clarify|date=April 2011}}<!-- what does 'improvement' mean?? -->  These radulae generally operate like 'brooms', brushing up loose microalgae.<ref name="Steneck1982"/>
** Formula: ∞ + 5 + R + 5 + ∞
** In case of a dominant lateral tooth:  ∞ + D + 4 + R + 4 + D + ∞
[[Image:Deroceras laeve radula 400 orcein.jpg|thumb|right|225px|Radula (magn. 400x) of the gray garden slug (''[[Deroceras laeve]]'') showing the chitinous lingual 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 radular formula of, for example, ''[[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 the [[Caenogastropoda]]).  These operate like 'rakes', scraping algae and gathering the resultant detritus.<ref name="Steneck1982"/>
** Formula : 2 + 1 + R + 1 + 2
* '''Ptenoglossan''' radula: rows with no central tooth but a series of several uniform, pointed marginal teeth (typical example : [[Epitonioidea]]).
** 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 completely absent. 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 radular types show the evolution in the gastropods from herbivorous to carnivorous feeding patterns. Scraping algae requires many teeth, as is found in the first three types.

Carnivorous gastropods generally need fewer teeth, especially laterals and marginals. The ptenoglossan radula is situated between the two extremes and is typical for those gastropods which are adapted to a life as parasites on [[polyp (zoology)|polyp]]s.

{|
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||[[File:Marstonia comalensis radula.png|left|thumb|A portion of the radula of ''[[Marstonia comalensis]]'' showing outer marginal teeth (on the left), inner marginal teeth and immediately next to them lateral teeth, central teeth. Scale bar is 20 μm.]]
||[[File:Marstonia comalensis radula 4.png|left|thumb|Inner marginal tooth. Scale bar is 10 μm.]]
||[[File:Marstonia comalensis radula 3.png|left|thumb|Lateral teeth. Scale bar is 10 μm.]]
||[[File:Marstonia comalensis radula 2.png|left|thumb|Central teeth. Scale bar is 10 μm.]]
|}