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Test shape is highly variable among different foraminifera; they may be single-chambered (unilocular) or multi-chambered (multilocular). In multilocular forms, new chambers are added as the organism grows. A wide variety of test morphologies is found in both unilocular and multilocular forms, including spiraled, serial, and milioline, among others.
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where the head-foot part of the body of the animal emerges for locomotion, feeding, etc. The term aperture is used for the main opening in gastropod shells, scaphopod shells, and also for Nautilus and ammonite shells.
The mollusc (or mollusk [spelling 1]) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater.
The body of a mollusc has a ventral muscular foot, which is adapted to different purposes (locomotion, grasping the substratum, burrowing or feeding) in different classes. [36] The foot carries a pair of statocysts, which act as balance sensors. In gastropods, it secretes mucus as a lubricant to aid movement.
Molluscs have such diverse shapes that many textbooks base their descriptions of molluscan anatomy on a generalized or hypothetical ancestral mollusc. This generalized mollusc is unsegmented and bilaterally symmetrical with an underside consisting of a single muscular foot. [67] [68]: 484–628 Beyond that it has three further key features.
The body whorl shows in this side view as the last complete turn of the shell spiral, the part of the shell that leads up to the aperture. The body whorl is part of the morphology of the shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk.
Unlike most other molluscs, there is no intermediate stage, or veliger, between the trochophore and the adult. Instead, a segmented shell gland forms on one side of the larva, and a foot forms on the opposite side. When the larva is ready to become an adult, the body elongates, and the shell gland secretes the plates of the shell.
The gastropod shell is part of the body of many gastropods, including snails, a kind of mollusc. The shell is an exoskeleton , which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage.