EVIDENCE FOR ENVIRONMENTAL INFLUENCE ON SECONDARYMETABOLITE PRODUCTION IN THE TROPICAL RED ALGA PORTIERIA HORNEMANNII

Daniel B. Matlock, David Ginsburg and Valerie J. Paul
University of Guam Marine Laboratory, UOG Station, Mangilao, Guam,USA 96923

Ochtodene, a halogenated monoterpene and the major secondary metabolitein Portieria hornemannii, is an effective feeding deterrent to herbivorousreef fishes on Guam. Levels of production vary widely from site to site.A reciprocal transplant study was conducted to determine the relative importanceof environmental versus genetic factors influencing the amount of ochtodeneproduced. The study sites, 35 km apart, were chosen for high (AnaeIs.) and low (Gun Beach) ochtodene levels, as shown by initial and finalfield samples. Intact plants were removed with a piece of the substrateand secured to bricks. Controls were returned to the water at theiroriginal sites, while experimental groups were transported to the reciprocalsites. After four weeks, individual plants were recovered and extractswere analyzed by GC-MS. At both sites controls showed a drop in ochtodeneproduction, presumably the result of handling at the beginning of the study. Plants transplanted from Anae Is. to Gun Beach, showed a decrease in ochtodenecontent beyond that of the controls. In contrast, those transplantedfrom Gun Beach to Anae Is. showed a significant increase in ochtodene content. If differences in secondary metabolite production were the result of geneticdifferences, one would expect the level of ochtodene in these transplantsto remain the same as in controls left at the original site. However,the results indicate that the conditions at Anae Is. cause elevated productionof ochtodene in transplanted individuals as well as those native to thesite, whereas the different conditions at Gun Beach result in decreasedproduction.