Astrophorid sponges have separate males and females. This should raise an eyebrow because most sponges are hermaphroditic, with an individual able to be both a male and a female. Astrophorid hermaphrodites are either rare or absent altogether. Instead, astrophorids go through a yearly reproductive cycle that includes a phase of gamete development (eggs develop in the females and sperm in the males). The egg development starts first and lasts more than two months. Then spawning happens, where male gametes (spermatozoans) and female gametes (oocytes) get released into the water. They must encounter each other by chance for fertilization to occur, so a lot of eggs go unfertilized.

Sponges achieve reproduction in a whole variety of ways. All sponges can reproduce sexually, meaning that egg and sperms cells get together for fertilization of the egg. How that happens varies from sponge to sponge. Usually, fertilization occurs outside of the female sponge in a meet-up of egg and sperm cells in the ocean (good luck!). Some sponges have internal fertilization, where the sperm cell swims to fertilize the egg inside the female. She may then lay eggs (oviparity) or release live larvae that have developed inside her body (viviparity). Most sponges are hermaphrodites, able to be both males and females. They might act as both sexes at the same time, or more likely one sex first and then the other. Many sponges sidestep fertilization at times by reproducing asexually. They either pinch off buds of new cells or break off clumps from their body. In either case, the cells reattach attach to a substrate and grow into adult sponges.