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Spirula spirula is a species of deep-water squid-like cephalopod mollusk. It is the only extant member of the genus Spirula , the family Spirulidae , and the order Spirulida . Because of the shape of its internal shell, it is commonly known as the ram's horn squid [ 3 ] or the little post horn squid .
However, most of other researchers do not agree that Nectocaris actually being a cephalopod or even mollusk. [140] [141] Early cephalopods were likely predators near the top of the food chain. [25] After the late Cambrian extinction led to the disappearance of many radiodonts, predatory niches became available for other animals. [142]
Shellfish allergy is among the most common food allergies."Shellfish" is a colloquial and fisheries term for aquatic invertebrates used as food, including various species of molluscs such as clams, mussels, oysters and scallops, crustaceans such as shrimp, lobsters and crabs, and cephalopods such as squid and octopus.
The hypobranchial gland is a glandular structure which is part of the anatomy of many mollusks, including several different families of gastropods, and also many protobranch bivalves. [1] This gland produces mucus as well as biologically active compounds. The cephalopod ink sac is a modified hypobranchial gland. [2]
Cephalopod limbs bear numerous suckers along their ventral surface as in octopus, squid and cuttlefish arms and in clusters at the ends of the tentacles (if present), as in squid and cuttlefish. [9] Each sucker is usually circular and bowl-like and has two distinct parts: an outer shallow cavity called an infundibulum and a central hollow ...
This structure exists in bivalves, cephalopods, polyplacophorans (chitons), and in aquatic gastropods such as freshwater snails and marine snails. [1] Certain molluscs, such as the bivalves, [ 2 ] possess paired ctenidia, but others, such as members of the Ampullariidae , [ 3 ] bear a single ctenidium.
Gomphoceras is a questionable nautiloid cephalopod genus assigned to the Oncocerida. The family to which it might belong is undetermined. Gomphoceras, named by Sowerby in 1839, is generally short but rapidly expanding, straight to slightly endogastric, with a gibbous body chamber such that all sides are convex. The aperture as vertically ...
About 700 living species of cephalopods have been identified. The nervous system of cephalopods is the most complex of all the invertebrates [4] and their brain-to-body-mass ratio falls between that of endothermic and ectothermic vertebrates. [5] The brain is protected in a cartilaginous cranium.