Ophryotrocha puerilis is a species of marine polychaete worms in the order Eunicida.

It is native to the northern Atlantic Ocean and the Mediterranean Sea and is the type species of the genus Ophryotrocha.

[1] Ophryotrocha puerilis starts life as a male but later changes sex to female.

Under certain circumstances it can change back to a male as a result of environmental cues; it switches sex if two female stages are put together, or if the tail of a female stage is removed, but it remains female if kept in isolation.

[2]