Biological Oceanography

Particles are detected during this sequence at a distance, before they touch any part
of the copepod. Detection likely is primarily olfactory. The principal evidence is that
receptors all over the mouth area are of a type shown to be olfactory in other
crustaceans. An important part of a convincing proof would be proper comparison of
the diffusivity of substances that might be coming from food particles with the time
and distance requirements set by the movies. Paffenhöfer and Lewis (1990) observed
that initial perception distance is greater as particle concentration decreases, which
they interpreted as expected for chemoreception. Phytoplankton cells are thought to
have a phycosphere about them, a boundary layer in which cell products are diffusing
away from them at the slow rates of molecular diffusion. Price and Paffenhöfer (1984)