- Sponges reproduce by both asexual and sexual means. Most poriferans that reproduce by sexual means are hermaphroditic and produce eggs and sperm at different times. Sperm are frequently "broadcast" into the water column. 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. Some sponges release their larvae, where others retain them for some time. Once the larvae are in the water column they settle and develop into juvenile sponges. Sponges that reproduce asexually produce buds or, more often, gemmules, which are packets of several cells of various types inside a protective covering. Fresh water sponges of the Spongillidae often produce gemmules prior to winter. These then develop into adult sponges beginning the following spring.
- Calcareous Sponges reproduce asexually by regeneration and through the process of budding. Both are a type of reproduction that results in a genetic clone. In the case of budding, the sponges produce a cluster of cells known as a gemmule that is covered in a hard coating, which keeps the offspring protected from harsh weather as well as climate changes. Regeneration is the ability of a sponge to grow a totally new and complete adult from a small piece of the adult sponge that has been torn loose. This process is used for commercial reasons as well. Although Calcareous sponges are asexual reproducing organism, they are also able to reproduce sexually.
- Sperm are taken into an organism with water, and then must make their way to eggs within the organism. After fertilization, the larvae are incubated for a relatively long time so they even form rudimentary spicules before being released as parenchymella larvae. These differ from other sponge larvae in lacking flagella or any other method of locomotion. Hexactinellids cluster to an unusually high degree, suggesting that larvae do not drift far before settling. After a larva lands on the ocean floor, it metamorphoses, and the adult sponge begins to grow. Hexactinellids are known for prolific budding.
-Methods of asexual reproduction include both budding and the formation of gemmules. In budding, aggregates of cells differentiate into small sponges that are released superficially or expelled through the oscula. Gemmules are found in the freshwater family Spongellidae. They are produced in the mesohyl as clumps of archeocytes, are surrounded with a hard layer secreted by other amoebocytes. Gemmules are released when the parent body breaks down, and are capable of surviving harsh conditions. In a favorable situation, an opening called the micropyle appears and releases amoebocytes, which differentiate into cells of all the other types.