(a) In open blood circulatory system, blood is pumped by the heart, through large vessels, into open spaces or body cavities called sinuses. Example includes insects, spiders, prawns and most mollusks.
(b) Closed circulatory system is more efficient as it uses much less blood for even higher and faster levels of distribution. Since oxygenated blood may reach the extremities of the body much faster than with an open system, organisms with a closed system may metabolize much faster, allowing them to move, digest and eliminate wastes much more quickly.
Figure: Open circulatory system of cockroach
