Friday Fellow: Persian Carpet Flatworm

ResearchBlogging.orgby Piter Kehoma Boll

A flatworm again, at last! Not a land planarian, but a flatworm nonetheless.

If there is a group of flatworms that may put land planarians in second plan regarding beauty, those are the polyclads. Living in the sea, especially in coral reefs, polyclads are colorful and curly and may be mistaken by sea slugs.

The species I’m introducing here today is Pseudobiceros bedfordi, commonly known as the Persian carpet flatworm or Bedford’s flatworm. It is about 8 cm long and lives in coral reefs along Australia, Indonesia, Philippines and adjacent areas. See how beautiful it is:

A flatworm (Pseudobiceros bedfordi). Raging Horn, Osprey Reef, Coral Sea

The Persian carpet flatworm with its beautiful colors. Photo by Richard Ling.*

The colorful pattern of this and many other polyclad species is likely a warning about their toxicity, although there are few studies regarding toxicity in these animals. Being active predators, polyclads may use their toxins as a way to subdue prey as well.

But the most interesting thing regarding the Persian carpet flatworm is its sexual behavior. As with most flatworms, they are hermaphrodites, so when two individuals meet and decide to have sex, they have to choose whether they want to play the male or the female role (or both). Unfortunately, most individuals prefer to be males, so those encounters usually end up in a violent fight in which both animals attack the partner with a double penis, a behavior known as penis fencing.


Two Persian carpet flatworms about to engage in penis fencing. Photo from Whitfield (2004), courtesy of Nico Michiels.**

At the end, the winner spurts its sperm onto the partner and leaves. The horrible part is yet to come, though. The sperm appears to be able to burn like acid through the receiver’s skin tissue in order to reach the inner tissues and thus swim towards the eggs. In some extreme cases the sperm load may be high enough to tore the receiver into pieces! If that’s not a good definition of wild sex, I don’t know what is.

See also: Gender Conflict: Who’s the man in the relationship?

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Whitfield, J. (2004). Everything You Always Wanted to Know about Sexes PLoS Biology, 2 (6) DOI: 10.1371/journal.pbio.0020183

Wikipedia. Pseudoceros bedfordi. Available at: <;. Access on November 24, 2016.

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*Creative Commons License
This work is licensed under a Creative Commons Attribution 2.0 Generic License.

**Creative Commons License
This work is licensed under a Creative Commons Attribution 2.5 Generic License.


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Filed under Behavior, Friday Fellow, worms

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