(full paper is archived in the Miller Library)
Title: Biological effects of zosteric acid in solution: Barnacle behavior and settlement, bacterial attactment, and sea urchin fertilization
Student Author(s): Grudzen, Corita R.
Location: Final Papers Biology 175H
Date: June 1994
Abstract: Zosteric acid (p-sulphooxy cinnamic acid) was studied for its role as a non-toxic antifouling agent. Cypris larvae of B. amphitrite were used to study the effects of the compound on larval chemotaxis, mobility, and settlement. Zosteric acid (ZA) elicited no chemotactic response from the larvae and therefore it does not appear to inhibit settlement by deterrence. ZA and sodium acetate, a weak acid with a similar pKa, did both cause larval immobility, possibly acting as weak acids and changing intracellular pH. Both pH neutralized (8.0) and unbuffered ZA were shown to inhibit settlement by up to 30%. Because the presence of microbial films can act as settlement cues for further fouling by both larval invertebrates and algae, ZA's effect on bacterial attachment was also investigated. Both zosteric acid, a sultafed phenolic ester, and p- coumaric acid, an unsulphated analog of ZA, were found to suppress bacterial attachment. Therefore, it can be concluded from this study that the sulphate moiety is not the necessary component for inhibiting bacterial adherance. The effects of ZA were also assayed on the attachment of sperm to the egg in the fertilization of the sea urchins Strongylocentrotus purpuratus and Litichinus pictus. It was found that the sulphate group on the ZA is necessary for the inhibition of fertilization. Another fertilization experiment, in which Protease was used to remove the vitelline layer of the egg, showed that ZA may inhibit fertilization by binding to the egg receptors on the vitelline layer, thus blocking sperm from attaching. In conclusion, it should be noted that ZA has a wide variety of effects and more than one mode of action. Multiple mechanisms seem to be involved, both individually and synergystically, in producing ZA's antifouling effect.