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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 four most universal features defining modern molluscs are a soft body composed almost entirely of muscle, a mantle with a significant cavity used for breathing and excretion, the presence of a radula (except for bivalves), and the structure of the nervous system. Other than these common elements, molluscs express great morphological ...
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.
Cephalopod radulae are known from fossil deposits dating back to the Ordovician. [103] They are usually preserved within the cephalopod's body chamber, commonly in conjunction with the mandibles; but this need not always be the case; [104] many radulae are preserved in a range of settings in the Mason Creek. [105]
The radula in this species is longer than the shell itself. It contains 1,920 teeth in 160 rows of 12 teeth each. It contains 1,920 teeth in 160 rows of 12 teeth each. Patella vulgata is found attached to firm substrates from the high shore to the edge of the sublittoral zone, although it predominates in areas of wave action.