Shell-less Molluscs

Although most molluscs have a protective shell, a number of genera and species are in the process of gradually loosing their shell.

Some molluscs with only a trace of a shell are the octopus and kin, and some false limpets.

In some molluscs, there is little or no evidence of a shell at all. Some examples are the sea slugs, sea hares and nudibranchs. The nudibranchs are the most gaudy, conspicuous and colourful of all the molluscs.

This has occurred in a number of groups.

Question:

Why might "loosing" a shell be advantageous to some molluscs ?

Molluscs
Shell-less Molluscs

Sydney Sea Cow

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