This zoosporangium is of Halophytophthora masteri, the only species of Halophytophthora that exhibits both a pop- out plug and a vesicle at zoospore release. In this photo, the plug has been blasted away, but the vesicle is the windsock-like thing sticking out from the mouth of the sporangium. The just- released zoospores are the silvery ovoids swimming around mostly below and to the right of the sporangium. The zoospores are about 7 x 14 µm in size. H. masteri is a specialist- decomposer of leaves of black-mangrove trees (Avicennia germinans). My friend Akira Nakagiri and I named this species after Manny Master (2nd from left; others are Dick the R/V CALANUS mate, SYN, and Jack Fell), one of the authors of a key paper in marine oomycotology (Fell & Master, 1975, Can. J. Bot. 53:2908-2922). Manny died too early, of cancer, in 1994. See Nakagiri et al., 1994, Two new Halophytophthora species, H. tartarea and H. masteri, from intertidal decomposing leaves in saltmarsh and mangrove regions. Mycoscience 35:223-232.