Definition: muscular waves propelling an animal over a mucus layer overlaying the substrate; alternating regions of muscular contraction and expansion create traveling waves that shear the mucus, resulting in translation of the animal.
Definition: Direct developers are characterized by young that resemble the adult form even in early stages of development. The larval stages of marine direct developers generally have very low dispersal potential.
Definition: Capable of creating a new organism by combining the genetic material of two gametes, which may come from two parent organisms or from a single organism, in the case of self-fertilizing hermaphrodites.
Definition: Relative to pinhole eyes, lens eyes have greatly improved resolution and image brightness. The lens converges incoming rays of light, thereby reducing the angle over which each photoreceptor receives light, and forming an image focused on the retina. Most lens eyes have "accommodation"; they can focus an image either by physically moving the lens toward or away from the retina or by using eye muscles to adjust the shape of the lens.