Mystery tubes coiled around deep-water tropical gorgonians: fecampiid cocoons (Platyhelminthes: Fecampiida) resembling Solenogastres (Mollusca).

During the examination of a large suite of tropical deep-water molluscs, a number of Solenogastres were found, some of them typically curled around gorgonian stems. A subsequent closer examination of the Solenogastres revealed another type of object also curled around the gorgonians, which strongly resembled Solenogastres but lacked their external features. These objects proved to be cocoons with egg capsules, each containing two eggs or young larvae, typical of the parasitic platyhelminth group Fecampiida.