PREDATION, COVER, AND CONVERGENT EVOLUTION IN EPIPELAGIC OCEANS

The factor of most importance to the structure of epipelagic oceanic c ommunities is the absence of cover and the inability to hide from pred ators in surface waters during the day (Elton, 1939). Visual predation in an environment devoid of cover has resulted in convergent evolutio n into only six modal adaptive patterns. Large, fast, visual predators roam the water, 1) alone or in 2) schools, and they eat anything of a ppropriate size that they see. Prey escape only by dint of 3) very sma ll size, 4) invisibility due to tissue transparency, 5) diurnal vertic al migration, or by 6) exploitation of the sea surface. The sensory ec ology and physiology of zooplankton are different from that of all oth er animal categories in all other habitats. Epipelagic zooplankton are either extremely small animals, with small and structurally simple se nse organs, or they are large, with gelatinous, transparent bodies whi ch often lack sense organs.