Dorid nudibranch elaborates its own chemical defense.

@article{Cimino1983DoridNE,
  title={Dorid nudibranch elaborates its own chemical defense.},
  author={Guido Cimino and Salvatore De Rosa and Salvatore de Stefano and Giuseppe Sodano and Gaetano Villani},
  journal={Science},
  year={1983},
  volume={219 4589},
  pages={1237-8}
}
A biosynthetic experiment with mevalonic acid labeled with carbon-14 showed that the nudibranch Dendrodoris limbata elaborates polygodial, a sesquiterpenoid dialdehyde stored in the mantle, which constitutes its chemical defense against predators. Previously described nudibranchs drew defensive chemicals from their preys.