Chemical defense in the egg masses of benthic invertebrates: An assessmentof antibacterial activity in 39 mollusks and 4 polychaetes

Many marine invertebrates deposit benthic egg masses that are potentially v ulnerable to microbial infection. To help counter this threat these species may have evolved some form of chemical protection for their encapsulated e mbryos. In this study the egg masses from 7 marine mollusks were tested for antibacterial activity against 4 marine pathogens: Enterococcus sericolici da, Vibrio anguillarum, Vibrio alginolyticus, and Vibrio harveyi. Extracts from all of these egg masses were found to inhibit the growth of at least 1 marine bacterium at concentrations that approximate the natural concentrat ion of extract in the egg masses. The egg masses of 39 mollusks and 4 polyc haetes were then tested for antibacterial activity against 3 human pathogen ic bacteria; Escherichia coli, Staphylococcus aureus, and Pseudomonas aerug inosa. Activity was detected in the egg masses from 34 species, including 2 polychaetes and mollusks from two classes and 18 families. Antibacterial a ctivity in molluskan egg masses was found to extend across the marine, estu arine, freshwater, and terrestrial environments. Both gelatinous egg masses and tough egg capsules were found to inhibit microbial growth, suggesting that physical protection alone may not be sufficient to protect the eggs. A ntimicrobial activity was observed in the fresh egg masses but not in the w ell-developed egg masses of a subset of species. The results of this study indicate that a wide range of invertebrates use chemical defense to protect their early stage embryos against bacterial infection. (C) 2001 Academic P ress.