By cooperatively moving their flagella, choanocytes filter particles out of the water and into the
spongocoel, and out through the
osculum. This improves both respiratory and digestive functions for the sponge, pulling in oxygen and nutrients and allowing a rapid expulsion of carbon dioxide and other waste products. Although all cells in a sponge are capable of living on their own, choanocytes carry out most of the sponge's ingestion, passing digested materials to the
amoebocytes for delivery to other cells. Choanocytes can also turn into
spermatocytes when needed for sexual reproduction, due to the lack of reproductive organs in sponges (amoebocytes become the
oocytes). ==Evolutionary significance==