How does sperm reach an egg in sexual reproduction by animal sponges?

In sexual reproduction, sponges release flagellated sperm from their body into the water, where they are carried by currents to another sponge. Upon entering the recipient sponge, the sperm is captured by a specialized flagellated cell known as a choanocyte, or collar cell.123

Once the choanocyte engulfs the sperm, it loses its collar and flagellum and transforms into a carrier cell. This cell then migrates through the sponge’s tissue to reach a matured egg. Fertilization is achieved when the carrier cell fuses with the egg. Following fertilization, the resulting embryo develops into a larva that is eventually released into the water to settle and grow into a new adult sponge.231