First evidence of self-fertilization in a marine microturbellarian (Platyhelminthes)

The reproductive strategy of the simultaneous hermaphrodite Pseudomonocelis paupercula (Platyhelminthes: Proseriata) was investigated using multiple approaches including breeding experiments, anatomical reconstruction, and parentage analysis of offspring. The 18 allozyme loci tested were monomorphic. Conversely, the ISSR markers showed differences among the populations, and allowed us to ascertain whether the offspring were derived from selfing or cross-breeding. The results suggest that selfing is the most common mode of reproduction in this species, with only 8% of the offspring resulting from cross-reproduction. Age at first reproduction of selfers does not differ from that of paired, potentially cross-breeding, specimens. The presence of sperm in the female ducts of individuals that have been isolated since birth suggests the existence of a connection between the male and female reproductive systems that allows self-fertilization. Habitat is suggested to be the key factor shaping the reproductive strategy of the species. P. paupercula is found in highly fragmented brackish-water microhabitats, and selfing may allow for colonization of new habitats that can start from single, unfertilized specimens.

► The reproductive strategy of an interstitial microturbellarian was investigated.
► Methods included breeding experiments and parentage analysis of offspring.
► Results showed that over 90% of offsprings were derived from selfing.
► The species occurs in microhabitats; selfing allows colonization by single specimens.