Alarm pheromones from the marine opisthobranchNavanax inermis

Abstract

When molested, the marine opisthobranchNavanax inermis secretes into its slime trail, a bright yellow mixture of three major compounds and several closely related minor substances. Collectively, these compounds induce an avoidance-alarm response in a trail-followingNavanax at the concentration limits of 1 × 10−5 M. The three major compounds have been isolated and identified as 10-(3′-pyridyl)-3E,5E,7E,9E-decatetraen-2-one (navenone A), 10-phenyl-3E,5E,7E,9E-decatetraen-2-one (navenone B) and 10-(4′-hydroxyphenyl)-3E,5E,7E,9E-decatetraen-2-one (navenone C). The minor constituents of the mixture are proposed as the 3Z,5Z,7E,9E-isomers and the 3-methyl homologs of navenones A and B. The navenones appear to be produced in a specialized gland referred to in earlier studies as the “yellow gland” and to communicate the presence of predators within the species.