Persian carpet flatworms

Persian carpet flatworms

This week’s topic is about the Persian carpet flatworm (pseudobiceros Bedfordi).

The Persian carpet flat worm is a species of marine polyclads located around the tropical reefs of Australia and up through Asia. It gets its name from the colour patterns displayed on its back that look remarkably like a Persian carpet.  Although this seems rather normal, what is unusual is that they are hermaphroditic, meaning each individual carries both male and female sexual organs, including a pair of side by side penises (Milius, 2006).

The behaviour when copulation occurs is known as fencing. They fight each other with their penises trying to stab and insert semen into the back of the other, without been stabbed itself. When one is stabbed by the other, the semen burns a hole through skin, making its way to the eggs.  The reason for the semen being placed on the back is the flat worm has reproductive tracks that open but they do not lead to the eggs.  The flat worm that absorbs the semen then becomes the ‘mother’. This unusual mating ritual is said to evolved due to a lack of partner options, by both obtaining male and female reproductive organs there is a higher chance of each individual been a suitable partner (Milius, 2006).

As for the fencing behaviour, the care of offspring is far more taxing than to be the inseminator. Once copulation is finished, which is said to last for up to an hour, the “father” will simply swim off whereas the “mother” will immediately eat (Milius, 2006).    

References:

Milus, S 2006, ‘Battle of the hermaphrodites’, Science News, Vol. 170, no. 12, pp. 186-188.