ZIMMER, R.K.*; ZIMMER, C.A.: Chemical Information Flow in Aquatic and Terrestrial Environments

Understanding the mechanisms by which environmental chemical signals mediate various life-history processes can lead to important insights about the ecology and evolution of organisms. For chemical signals released into the environment, establishing the principles that control chemical production and transport is critical for interpreting biological responses to these stimuli within appropriate natural-historical contexts. The physics governing chemical transport are similar in air and water and can be described by essentially the same equations. Still, because the molecular viscosity of an aerosol is so much smaller than that of an aqueous solution, bulk transport (called ‘advection’) and turbulent mixing of signal molecules are generally much faster in air. Such similarities and differences between the properties of the fluid media lead to convergence or divergence among navigational strategies used by macroscopic animals in turbulent odor plumes. Strong effects of advection and turbulence also determine transport of chemical signals at microscopic scales, such as in pheromonal communication between sperm and egg. Here, laminar shears stretch or distort chemical concentration fields and thus substantially modify broadcast distances of signals relative to those produced by molecular diffusion. Independent of organism size or fluid medium, physics tightly constrains the evolution of chemical-signaling processes and dictates the mechanics of orientation.