Structure of bryostatin 20: a symbiont-produced chemical defense for larvae of the host bryozoan, Bugula neritina.

Larvae of the marine bryozoan Bugula neritina are defended against potential predators by high concentrations of bryostatins, which are produced by a bacterial symbiont of the bryozoan. From the larvae of B. neritina, three bryostatins, bryostatin 10 (1), the novel bryostatin 20 (2), and an as yet uncharacterized bryostatin, were isolated that were unpalatable to fish. These deterrent bryostatins represent the first example from the marine environment of a microbial symbiont producing an antipredator defense for its host. The structure of bryostatin 20 (2) was determined by spectral comparison with previously described bryostatins.