Table of Contents
In which molluscs is the shell absent?
gastropods
Some gastropods have no shell at all, or only an internal shell or internal calcareous granules, and these species are often known as slugs. Semi-slugs are pulmonate slugs with a greatly reduced external shell which is in some cases partly covered by the mantle.
Which mollusc has internal shell?
slugs
The gastropods are the most numerous molluscs and account for approx. 80 % of the total. The shell is mostly large enough to cover and protect all the soft parts from predation and dessication. The slugs have an internal shell, internal chalk granules or no shell at all.
Do mollusks have an internal shell?
In general, mollusks have 3 body regions: a head, a visceral mass, and a “foot.” The head contains the sense organs and “brain,” while the visceral mass contains the internal organs. Mollusks usually have a shell (although some do not). Mollusks also have an extension of the body wall called the mantle.
Do mollusks have an internal or external shell?
Mollusks are aquatic species that are not fish. They include snails, scallops, and squids. Mollusks have a hard outer shell that covers the top of the body and encloses the internal organs. Mollusks have unique features such as the mantle and radula.
Do mollusks change their shells?
To make space for their growing body, molluscs have to gradually enlarge and extend their shells by adding new layers of those building blocks – calcium, carbonate and proteins. The newest part of the sea snail’s shell, for example, is around the opening where the animal pokes out.
What is an example of a mollusc without a shell?
Mollusks without shells include squid, banana slugs, and octopi.
What mollusk have to shells?
The name ‘bivalve’ translates to ‘two shells’, so this is easy to remember. Oysters are often grown on oyster farms, like the one shown here. You are also probably familiar with snails; they have shells, too! Snails, snugs, limpets, and abalones are all found within the gastropods subcategorization of mollusks.
Do mollusks have segmented bodies?
Mollusks may be primitively segmented, but all but the monoplacophorans characteristically lack segmentation and have bodies that are to some degree spirally twisted (e.g. torsion). The Pelecypoda are the bivalve mollusks and include oysters, clams, and scallops.
Are mollusks arthropods?
Mollusks are the soft-bodied invertebrates with one or two shells, whereas arthropods are the invertebrates with segmented bodies, jointed legs and appendages. Mollusks include snails, clams and squids while arthropods include spiders, mites, scorpions, shrimps, crabs, lobsters, insects, etc.