In general, sponges feed by filtering bacteria from the water that passes through them. Some sponges trap roughly 90 percent of all bacteria in the water they filter. Other sponges, in particular hexactinellids , appear to be less efficient at capturing bacteria and may specialize in feeding on smaller bits of organic matter. Still other sponges harbor symbionts such as green algae , dinoflagellates , or cyanobacteria , from which they also derive nutrients. They capture small crustaceans with their spicules which act like Velcro when they come in contact with the crustacean exoskeletons.
Cells then migrate around the helpless prey and digestion takes place extracellularly.
Most poriferans that reproduce by sexual means are hermaphroditic and produce eggs and sperm at different times. That is, sperm are created, concentrated and sent out the excurrent openings, sometimes in masses so dense that the sponges appear to be smoking. These sperm are subsequently captured by female sponges of the same species. Inside the female, the sperm are transported to eggs by special cells called archaeocytes . Fertilization occurs in the mesenchyme and the zygotes develop into ciliated larvae.