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The radula (US: / ˈ r æ dʒ ʊ l ə /; pl.: radulae or radulas) [1] is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. [2] It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus .
In terrestrial pulmonate gastropods, eye spots are present at the tips of the tentacles in the Stylommatophora or at the base of the tentacles in the Basommatophora.These eye spots range from simple ocelli that cannot project an image (simply distinguishing light and dark), to more complex pit and even lens eyes. [6]
The mollusc does not elongate when crawling and the location of the head is revealed when it thrusts out its rolled rhinophores from beneath the shell. At the base of the rhinophores are a pair of eyes, and beneath is a cleft which contains the mouth. The radula is broad and is armed with many small teeth.
The buccal mass is the first part of the digestive system, and consists of the mouth and pharynx. The mouth includes a radula, and in most cases, also a pair of jaws. The pharynx can be very large, especially in carnivorous species. Many carnivorous species have developed a proboscis, containing the oral cavity, radula, and part of the ...
The radula of a gastropod is usually adapted to the food that a species eats. The simplest gastropods are the limpets and abalone, herbivores that use their hard radula to rasp at seaweeds on rocks. Many marine gastropods are burrowers, and have a siphon that extends out from the mantle edge.
This organ is involved in chemoreception - that is, in judging the nature of food or the substratum. In this sense, it can be considered a 'smell' or 'taste' organ; food is sensed before each stroke of the radula. [1] Nerve cells from the subradular organ join into the buccal nerves. [2]
The radula is used to scrape microscopic algae off the substratum. The mouth cavity itself is lined with chitin and is associated with a pair of salivary glands. Two sacs open from the back of the mouth, one containing the radula, and the other containing a protrusible sensory subradular organ that is pressed against the substratum to taste for ...
Scallops have up to 100 simple eyes. The molluscs have the widest variety of eye morphologies of any phylum, [1] and a large degree of variation in their function. Cephalopods such as octopus, squid, and cuttlefish have eyes as complex as those of vertebrates, while scallops have up to 100 simple eyes.