For more than a century, it has been pointed out that most features of the original description of Ophryotrocha puerilis Claparède & Mecznikow, 1869, probably based on a mixed population of two sympatric species, agree better with the subsequently described O. labronica La Greca & Bacci, 1962. Although O. labronica was described as a protandrous hermaphrodite that could self-fertilize, the widely distributed species is mainly gonochoristic. We will designate neotypes, redescribe these two polychaetes and review their reproduction and development to remove any confusion and uncertainty surrounding the identity of these two well-known polychaetes. We will also discuss the growth and replacement of the maxillary apparatus and the morphology and distribution of the rosette glands, providing support for the molecular phylogeny of selected Ophryotrocha species.
