The paired pedal protractor and retractor muscles operate the animal's foot.

In gastropods, for example, the retractor muscles connect to the shell via tendon cells.

If disturbed by touch, water movement, or shadow, the tentacular crown can be quickly withdrawn entirely within the tube, by retractor muscles.

Male part of the genitalia with a single retractor muscle, without flagellum or caecum.

A set of retractor muscles help pull the proboscis back inside the sheath once feeding is completed.

There are no muscles attaching them to the basal disc but they do have strong retractor muscles.

As it grows it can use these threads and its retractor muscle to burrow deeper into the sediment.

The introvert can be retracted into the trunk by the retractor muscles of which there are usually four but occasionally three.

However, regardless the number, larval retractor muscles make no contribution to the post-metamorphic columellar muscle in opisthobranchs.