Mollusks have an open circulatory system. These animals use their hearts to pum blood into their bodies at certain spaces. The space is known as a hemocoel, which is also known as the blood cavity. Mollusks have a coelom a small area around the heart like the Cody cavity in chordates. Cephalopods however, whose activities require that the cells be supplied with large amounts of oxygen and food, and therefore have a closed circulatory system. They have three hearts that pump blood into the gills. These animals tend to be smaller, therefore we can assess that since they haven't grown much, that they didn't need a closed circulatory system.
Cuttlefish- Cuttlefish have a closed circulatory system due to that they are cephalopods. They have a very unique feature in their cardiovascular system. They have three hearts that transfer blood throughout the animal. Two of the hearts supply blood to the gills, while one feeds the rest of the body.
Clams- Clams have an open circulatory system. Blood is pumped out of the heart and goes through a few large vessels to the tissues where it exits the arteries and enters large spaces where it passes over the cells of the various organs. It then collects into large internal spaces called lacunae from which it passes through the kidney and gills, ultimately returning to the heart to complete the circuit.
Snails- As in other mollusks, the circulatory system of gastropods is open, with the fluid, or haemolymph, flowing through sinuses and bathing the tissues directly. The haemolymph typically contains haemocyanin, and is blue in color. A snail's heart is located in its shell. This shows an evolutionary advance to protect the most valuable organ.
Video of a clams anatomy and cardiovascular system
Cuttlefish- Cuttlefish have a closed circulatory system due to that they are cephalopods. They have a very unique feature in their cardiovascular system. They have three hearts that transfer blood throughout the animal. Two of the hearts supply blood to the gills, while one feeds the rest of the body.
Clams- Clams have an open circulatory system. Blood is pumped out of the heart and goes through a few large vessels to the tissues where it exits the arteries and enters large spaces where it passes over the cells of the various organs. It then collects into large internal spaces called lacunae from which it passes through the kidney and gills, ultimately returning to the heart to complete the circuit.
Snails- As in other mollusks, the circulatory system of gastropods is open, with the fluid, or haemolymph, flowing through sinuses and bathing the tissues directly. The haemolymph typically contains haemocyanin, and is blue in color. A snail's heart is located in its shell. This shows an evolutionary advance to protect the most valuable organ.
Video of a clams anatomy and cardiovascular system