A Question of Taste: Crypsis and Warning Coloration in Freshwater Zooplankton Communities

Visual predation by fishes appear to have driven prey towards divergent extremes, with two of the alternative avenues dependent upon initial palatability. On the one hand, selective predation upon initially large—bodied, strongly pigmented, and highly palatable zooplankton has selected for reduced conspicuousness (smaller body size at maturity, increased transparency of tissues). On the other hand, selective predation upon initially pigmented, yet mildly unpalatable groups (e.g., water mites), has selected for enhanced conspicuousness and increased distastefulness. At the basis of these two diverging selective responses lies the initial mouthing experiences of the predator, i.e., whether the image of the prey is associated with pleasure (reward) or with pain (punishment). While aposematic coloration seems limited among zooplankters to special cases, chemical defenses appear to be more widespread than commonly believed.