The morphology and morphogenesis of a new Australian metopid ciliate, Lepidometopus platycephalus nov. gen., nov. spec., were studied using live observation, various silver impregnation methods, scanning electron microscopy, and morphometry. The new genus is outstanding in having epicortical scales (lepidosomes) and a strongly flattened and distinctly projecting preoral dome. Diagnostic features of L. platycephalus include a small, reniform body carrying an elongated caudal cilium, about 11 ciliary rows, and an adoral zone composed of an average of 11 polykinetids. The morphogenesis of L. platycephalus matches data from other metopids in that (1) the body is drastically re-shaped, (2) the parental oral structures are reorganized but do not contribute to the daughter oral ciliature, (3) the opisthe’s adoral polykinetids originate pleurotelokinetally, (4) the opisthe’s paroral membrane is formed via re-arrangement of the posterior portion of the first two perizonal rows, and (5) the opisthe’s perizonal stripe is made by three parental perizonal rows and two dorsolateral ciliary rows. The morphogenetic data corroborate phylogenetic analyses in that caenomorphids are only superficially similar to metopids; metopids and clevelandellids are closely related; and litostomateans are the best candidates for a sister group of the metopid-clevelandellid assemblage within the SAL superclade.
Assays of protein contained in water-soluble fraction of encysting cells Colpoda cucullus Nag-1 by two-dimensional electrophoresis (2-D PAGE) and mass spectrometry (MS) revealed that the amount of β-tubulin abruptly increased in 2.5–10 h after encystment induction. Judging from the results that total α-tubulin content did not decrease much until 12 h after encystment induction, the result indicates that disassembly of microtubules may occur soon after encystment is induced. Therefore, we tried to visualize dynamics of microtubules. Immunofluorescence microscopy using anti-α-tubulin antibody indicated that disassembly of axonemal microtubules of cilia became within 1.5 h after encystment induction, and resorbed in 3 days. Although the cytoplasmic microtubules failed to be visualized clearly, encystmentdependent globulation of cells was promoted by taxol, an inhibitor of disassembly of microtubules. It is possible that a temporary formation of cytoplasmic microtubules may be involved in cell globulation. The phosphorylation level of actin (43 kDa) became slightly elevated just after encystment induction. Lepidosomes, the sticky small globes surrounding encysting cells, were vividly stained with Acti-stain 555 phalloidin, suggesting that 43-kDa actin or its homologues may be contained in lepidosomes.
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