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Fine-Structure Of Minchinia Sp (Haplosporida) Sporulation In Mud Crab, Panopeus-Herbstii, Frank O. Perkins

VIMS Articles

Morphogenetic changes which accompany sporulation of Minchinia sp. in the mud crab (Panopeus herbstii) are described. Small (4-19 /-1m diameter) plasmodia, the precursor cells for the sporulation sequence, increase in size and numbers of nuclei per cell to form sporonts with a delimiting wall. Since widely divergent nuclear sizes (2.3-5.9 /-1m diameter) and paired small nuclei < 3 /-1m diameter) were observed in sporonts, it is suggested that karyogamy occurs followed by meiosis. Evidence for meiosis is the observation of synaptonemal-like complexes and polycomplex-like structures in sporont nuclei. Sporonts cleave into uninucleate sporoblasts following one of two pathways. In the presumably "normal" sequence, a cytoplasmic syncytium is formed followed by cleavage into uninucleate sporoblasts. In the other, sporont protoplasm is asynchronously "carved" into uni- or binucleate sporoblasts or sporoplasms as a result of delimitation at the surface and internally. Since aberrant spore formation was commonly observed in the latter type of sporont, its cleavage patterns are considered to be anomalous. A sporoplasm is then delimited in each sporoblast and spore maturation follows. Haplosporosomes were observed in plasmodia and spores, but not in intermediate cell stages. Mitotic apparati appear to be persistent through interphase in plasmodia and sporonts and consist of two spindle pole bodies connected by a bundle of micro tubules.