DOES WARNING COLORATION OCCUR IN NUDIBRANCHS

Direct evidence for the occurrence of aposematic (warning) coloration in nudibranch molluscs is reviewed and is shown to be inconclusive. Many species are conspicuously colored and are distasteful to possible predators, but there is very little evidence that they are avoided by predators because of their colours or that these colours give better protection than would cryptic colours. Indirect evidence for aposematism can be obtained by assuming that it occurs, predicting the consequences of this assumption, and then testing these predictions. Information to test most of these predictions is either not available or is inconclusive, but the strongest support for aposematism is the widespread occurrence of Batesian and/or Mullerian mimicry. It is concluded that warning coloration does occur in nudibranchs but that there is much scope for further experimental studies.