Two newhalophytophthora species,H. tartarea andH. masteri,from intertidal decomposing leaves in saltmarsh and mangrove regions

Two new pythiaceous fungi were obtained from decaying leaves submerged in saltmarsh environments of the east coast of the U.S.A., or fringing mangroves in the Bahama Islands, and are described here asHalophytophthora tartarea andH. masteri. The two species have superficially similar zoosporangia whose dehiscence tubes have ragged-looking apices. However, differences in fine structures and development of the dehiscence tube and plug, characteristics of the dehiscence plugs, and presence or absence of vesicles clearly distinguish the two species.Halophytophthora masteri is the only species ofHalophytophthora that has a zoospore release mechanism involving both an extruded plug and a vesicle. Cultural properties concerning growth and asexual reproduction at various salinities and temperatures are also different between the two, probably reflecting adaptation to their respective habitats. Though zoospore release inH. masteri occurs spontaneously from mature zoosporangia, it is remarkably enhanced inH. tartarea and alsoH. masteri by mildly dehydrating mature zoosporangia followed by rewetting with seawater, which suggests a possible relation between the asexual reproduction of these oomycetes and the tidal rhythm in their natural habitats.