Multiple Mariner transposons in flatworms and hydras are related to those of insects.

Three flatworm species, the freshwater Dugesia tigrina and the marine Stylochus zebra and Bdelloura candida, and two freshwater hydra species, Hydra littoralis and H. vulgaris, were found to have many distinct representatives of the mariner family of transposable elements in their genomes. In several cases the closest relatives of these mariners are ones known previously from insect genomes, supporting the view that transposons of this family are capable of horizontal transfer across phyla, and hence must be capable of functioning in such diverse host environments. Twenty other invertebrates representing the major phyla did not appear to have mariners of these kinds in their genomes.