Circulation/Internal Transport

The oxygen and nutrients that are taken in by molluscs are carried through it’s body by blood. The blood is not always contained within vessels, making it an open circulatory system. This means that, when the blood is not being contained in the blood vessels, it works its way through the body tissues in sinuses (open spaces). This type of circulatory system works well for molluscs who are slow moving, or sessile, for example clams, however it is not sufficient for more motile molluscs like squid and octopi, which function by means of a closed circulatory system.