The sessile ciliate protozoan Folliculina simplex Dons can attach itself to the shells of large gastropod larvae and is found as an epizoite on the veligers of Tanna galea, Cymatium nicobaricum, Charonia variegata, Cymatium parthenopeum, and several other Cymatiidae. Among all the planktonic samples taken throughout the North Atlantic, 12.6% included prosobranch veligers bearing folliculinid ciliates....
Scheltema, Rudolf S.. 1973. "Dispersal of the protozoan Folliculina simplex Dons (Ciliophora, Heterotricha) throughout the North Atlantic Ocean on the shells of gastropod veliger larvae." Journal of Marine Research 31, (1). https://elischolar.library.yale.edu/journal_of_marine_research/1250