Torsion

Definition

Torsion is a developmental process in gastropod molluscs during which the visceral mass rotates 180 degrees. This results in the animal's anus and mantle cavity being positioned above its head.

5 Must Know Facts For Your Next Test

1. Torsion occurs during the larval stage of gastropod development.
2. It significantly impacts the internal anatomy, causing asymmetry.
3. Torsion helps protect the head by positioning the shell’s opening forward.
4. Despite torsion, some adult gastropods may undergo detorsion, partially reversing this rotation.
5. Torsion can complicate waste expulsion and respiration due to the new positioning of organs.

Review Questions

• What stage of gastropod development does torsion occur?
• How does torsion affect the symmetry of a gastropod's body?
• What are two potential advantages and disadvantages of torsion?

Related terms

Gastropod: A class within the phylum Mollusca that includes snails and slugs.

Mantle Cavity: The central feature in molluscs where respiratory organs are located.

Detorsion: A process where gastropods partially or fully reverse their initial torsional rotation.