These canals exist to move water through the sponge's body. Lining these canals are special collar cells. The collar cells force water through the sponge which brings oxygen and nutrients while removing carbon dioxide and waste. The collar cells are how sponges feed. The water brings with it bacteria and other organisms which the cells capture and filter out.
Most sponges are both male and female.
During mating, one sponge plays the male role while the other plays the female role, even though both are capable of playing either role. A sponge may play a female role one time and a male role the next time. After internal fertilization, larvae is released. After floating around for a few days, they settle down and start growing. There are many different types of beautiful and colorful sponges.