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Summary The nuclei of the vampyrellid filose amoeba Lateromyxa gallica were investigated in trophozoites, early digestive cysts, reproductive cysts, and in developing resting cysts. Trophozoites possess numerous, minute, spherical nuclei in interphase. In early digestive cysts the nuclei enlarge and the morphology of the nucleolus changes. The digestive cysts develop into reproductive cysts. Karyokinesis takes place synchronously. The spindle is intranuclear and acentrical. In metaphase, the chromosomes are arranged in a distinct equatorial plate. The nuclear envelope remains intact at least until telophase. Shortly after karyokinesis the trophozoites leave the cysts. Cytokinesis regularly takes place when the trophozoites invade cells of Oedogonium . Under unfavorable conditions the trophozoites as well as the digestive cysts are able to form resting cysts. Nuclei of digestive cysts which begin to develop into resting cysts were found in the pachytene phase of meiosis, proved by synaptonemal complexes. Karyokinesis, probably the second meiotic division, was detected when the resting cyst was almost fully developed. From the results of our investigations, the vampyrellid filose amoebae can be regarded as sexual. |
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