Sex Changing Corals

In a recent study by Israeli and Japanese scientists, it has been discovered that 'Mushroom' or 'Plate' and 'Slipper' or 'Tongue' Corals (of the Fungiidae family) can repetitively change sex from male to female and back again, female to male on an annual basis! 

Fungia is a genus of mushroom, disc or plate corals in the family Fungiidae. Members of the genus are found growing on reefs in the Indo-Pacific. These corals are mostly solitary, some attaining 30 centimetres in diameter, with juveniles attaching themselves to rock and larger individuals then detaching to become free living. The discs are either round or oval and the central mouth, which is surrounded by tentacles, appears as a slit.

This scientific study involved two species of coral (Fungia repanda and Ctenactis echinata) that were collected, tagged and then kept in a lab until after the full moon when these would release sperm or eggs into the water as 'gamete explosions'. After this, these corals were then classified as being either male or female. Once correctly sexed, the corals were once again returned to the sea and the scientists repeated this laboratory experiment for the following 2 years. The subsequent 'gamete explosions' on these tagged corals revealed that they had indeed changed sex! In fact, 75% of the corals had changed sex in the first year and 80% the following year. As a result meant that some had returned back to the original sex they had been tagged with at the start of this study.

Being hermaphroditic can have great advantages. It allows a species to reproduce in the absence of either males or females. Being a sequential hermaphrodite, that is being able to switch from male to female, or vice versa, also has these advantages. Since fertility requires more energy as a female, due to producing energy-rich egg cells, this can only be done when sufficient energy and ocean conditions are available. So even when Fungia corals have little energy to reproduce, they still try to do so as males, until the conditions recover and they can return to being female again.