. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 82 T. S. WAKEFIELD ET AL granular, to half granular/half vesicular, to almost com- pletely vesicular) could be explained by symbionts caught in varying stages of the ecdysis. Similarly, such a cycle would also result in the sporadic appearance of flagella, as reported in some /// situ symbionts (Taylor, 1971a, b; Schoenberg and Trench, 1980). and the pres- ence of thecal vesicles, as reported in this paper. We also suggest that the delayed ecdysis cycle could be responsible for the multiple layers of apparent membranes that
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 82 T. S. WAKEFIELD ET AL granular, to half granular/half vesicular, to almost com- pletely vesicular) could be explained by symbionts caught in varying stages of the ecdysis. Similarly, such a cycle would also result in the sporadic appearance of flagella, as reported in some /// situ symbionts (Taylor, 1971a, b; Schoenberg and Trench, 1980). and the pres- ence of thecal vesicles, as reported in this paper. We also suggest that the delayed ecdysis cycle could be responsible for the multiple layers of apparent membranes that are often found just outside of the vegetative cell wall of in situ symbionts. Unlike those of cultured symbionts, the shed thecal plates and outer plasma membrane of in situ symbionts would not be discarded but would accumulate inside of the symbiosome membrane (Fig. 12). Such shed plates would appear as the accumulations of the apparent membranous material (ml) that has been observed between the outer symbiosome membrane and the vegetative cell wall of the symbionts (Taylor, 1968; Kevin ft til., 1969; Schoenberg and Trench, 1980; Tripodi and Santisi, 1982; -sm •KXttWWX^ftiWM^** cwl • pml tvl 1 (pml+tvl). •cw - pm tv Figure 12. A hypothesis for how multiple layers of membrane could accumulate within symhiosome membrane: step 1. Vegetative cell gives rise to motile "thecate" cell; cell wall disappears, step 2. Mo- tile cell undergoes ecdysis and sheds plasma membrane and thecal vesicles as the cell wall is reformed and new thecal vesicles form beneatli ii. ^:p ^ After several cycles, accumulated material from algal plasma membi .1, >uil ihecal vesicles appear as multiple membranes between the outei - mbiusnme membrane and the vegetative algal cell wall, cw = cell wall; ml = multiple layers of membrane; pin T symbiont plasma mcmlnaue; sm = surface of symbiosome membrane; tv = thecal vesicles. | figure adapted from Hohfeld and Melkonian. 1992.) Colley and Trenc
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