<jats:title>A little help from a friend</jats:title> <jats:p> The Hawaiian sea slug <jats:italic>Elysia rufescens</jats:italic> grazes on an alga called <jats:italic>Bryopsis</jats:italic> sp. The alga defends itself from predators using peptide toxins decorated with fatty acids, called kahalalides. Zan <jats:italic>et al.</jats:italic> wondered if a third party was involved in toxin production (see the Perspective by Mascuch and Kubanek). Within the alga, a species of bacterium with a very reduced genome was discovered to be a factory for the nonribosomal assembly of a family of kahalalides. The authors elucidated the pathways for generating this chemical diversity. It seems that the sea slug not only tolerates the toxins but, to protect itself from being eaten by fish, grazes on the alga to accumulate kahalalide. <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" related-article-type="in-this-issue" xlink:href="10.1126/science.aaw6732">eaaw6732</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6445" page="1034" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aax8964">1034</jats:related-article>