While there is little scientific documentation on the sexual reproduction within Aiptasia, general observations indicate the sexual reproduction may occur in two forms.
In the case of the well-studied Aiptasia pallida and Aiptasia pulchella, individuals are dioecious, meaning that individuals are of separate sexes. During spawning, anemones release their gametes into the water where fertilization occurs. The resulting zygote becomes a free swimming planula larva which eventually settles onto a suitable substrate and undergoes metamorphosis to become a small polyp. Newly produced larvae are aposymbiotic meaning they do not contain symbionts. The larvae or newly settled polyps acquire symbiotic algae from the environment.
In certain species of Aiptasia fertilization may be internal, in the coelenteron. Male gametes are released from male Aiptasia into the water column. These gametes are non-buoyant and settle to fertilize the female gametes within other Aiptasia. These gametes develop internal to the Aiptasia into Planula Larva, receiving nourishment from the hosting anemone. When conditions are optimal (light and nutrients are high), or during physical attack (as when an aquarist is attempting to remove them), these larva are released into the water column to start growing and colonizing other parts of the reef.
