pyrgomatids, but a recent study recorded evidence of living pyrgomatids in stylasterids, casting doubt on this idea. Life cycle Stony corals have a great range of reproductive strategies and can reproduce both sexually and asexually. Many species have separate sexes, the whole colony being either male or female, but others are hermaphroditic, with individual polyps having both male and female gonads. Some species brood their eggs but in most species, sexual reproduction results in the production of a free-swimming planula larva that eventually settles on the seabed to undergo metamorphosis into a polyp. In colonial species, this initial polyp then repeatedly divides asexually, to give rise to the entire colony. Asexual reproduction The most common means of asexual reproduction in colonial stony corals is by fragmentation. Pieces of branching corals may get detached during storms, by strong water movement or by mechanical means, and fragments fall to the sea bed. In suitable conditions, these are capable of adhering to the substrate and starting new colonies. Even such massive corals as Montastraea annularis have been shown to be capable of forming new colonies after fragmentation. This process is used in the reef aquarium hobby to increase stock without the necessity to harvest corals from the wild. Under adverse conditions, certain species of coral resort to another type of asexual reproduction in the form of "polyp bail-out", which may allow polyps to survive even though the parent colony dies. It involves the growth of the coenosarc to seal off the polyps, detachment of the polyps and their settlement on the seabed to initiate new colonies. In other species, small balls of tissue detach themselves from the coenosarc, differentiate into polyps and start secreting calcium carbonate to form new colonies, and in Pocillopora damicornis, unfertilised eggs can develop into viable larvae. Sexual reproduction The overwhelming majority of scleractinian taxa are hermaphroditic in their adult colonies. In temperate regions, the usual pattern is synchronized release of eggs and sperm into the water during brief spawning events, often related to the phases of the moon. In tropical regions, reproduction may occur throughout the year. In many cases, as in the genus Acropora, the eggs and sperm are released in buoyant bundles which rise to the surface. This increases the concentration of sperm and eggs and thus the likelihood of fertilization, and reduces the risk of self-fertilization. Immediately after spawning, the eggs are delayed in their