For these reasons, information on intertidal hydroids usually focuses on morphological adaptations of particular species (e.g., thickening of the
hydrocaulus in species of Leptothecata) to specific environments, such as intertidal habitats, where the water movements are stronger (e.g., Calder, 1991; Hughes, 1992; Rossi et al., 2000; Henry, 2002).