Defense strategies of marine and aquatic organisms

Abstract

Among the defense strategies of many marine organisms, there are both striking parallels to terrestrial organisms and unique defense compounds with remarkable structural complexity and toxicity. In analogy to plant and animal defense, marine organisms produce reactive dialdehydes such as caulerpenyne and 2,4,7-decatrienal acting as Michael acceptors that destroy the function of proteins. Like terrestrial organisms, some marine organisms store such highly reactive toxins as inactive precursors that are converted into toxins by enzymes in case of attack (activated defense). Many marine organisms make use of halogenated, in particular chlorinated and brominated, defense compounds. Related defense compounds may otherwise be only found among fungi and microorganisms. Highly complex marine toxins such as the polyethers brevetoxin and palytoxin comprise the most poisonous nonproteinogenic compounds. Generally, there is growing evidence that many such polyketide or nonribosomal peptide defense compounds may be of microbial origin produced by symbionts. Yet it is remarkable how the hosts gained resistance against these powerful toxins. Indeed it seems that adaptation to toxins among marine organisms is widespread so that many organisms can also feed on toxic organisms, sequester their toxins, and reuse them for own defense purposes.