Sponges are the simplest form of multi-cellular animal life. Often overlooked, they are an important component of reef systems and other marine habitats. Sponges are the filters of the sea, filtering the water as they pump it through a complex system of canals in their bodies, to collect small bacteria and particles of organic debris for food. Water circulation inside the sponge is achieved by the beating action of millions of tiny whip-like flagella on cells that line the canals. Sponges are generally hermaphrodites and can reproduce sexually through the production of swimming larvae that are released into the water via their outlet canals. The larvae later settle onto a substratum and grow to form an adult. Sponges may also reproduce asexually, via buds that break off the parent and develop into new adults. Small pieces of sponge detached during storms may also reattach and grow again.