Octopuses and mussels have very different circulatory systems, which significantly impact their mobility.
Octopuses have a closed circulatory system, which means their blood is contained within vessels. This system includes three hearts: two pump blood to the gills, and one pumps it to the rest of the body. The closed system allows for efficient oxygen delivery, which supports the high energy demands of their active lifestyle. This efficiency is crucial for their mobility, enabling them to move quickly and change direction rapidly, which is essential for hunting and escaping predators.
On the other hand, mussels have an open circulatory system, where blood is not entirely contained within vessels. Instead, it flows freely through cavities in their body. This system is less efficient at delivering oxygen and nutrients, which limits their mobility. Mussels are generally sedentary creatures, often attaching themselves to rocks or other surfaces and remaining in one place for most of their lives. Their limited mobility is sufficient for their lifestyle, which primarily involves filter feeding.
In summary, the closed circulatory system of octopuses supports their active and mobile lifestyle, while the open circulatory system of mussels is suited to their sedentary and less mobile existence.