As I have mentioned in the phylum slides sponges do not have cardiovascular systems but instead use a filtering system called a water based circulatory system that opens pores on the sponge called ostia that will create a current to draw water into the sponge so that it will reicieve oxygen from the water. In the ostias there are choanocyte that the water flows through and a flagellum at the end to keep the water moving and to catch any food. The water is then released through the top opening of the sponge called an osculum. An interesting fact about the giant barrel sponge is that it can live for over 2000 years old and have the nickname or redwoods of the sea.