KARYOLOGICAL INVESTIGATIONS ON THE VAMPYRELLID FILOSE AMEBA LATEROMYXA-GALLICA HULSMANN 1993

The nuclei of the vampyrellid filose amoeba Lateromyxa gallica were in vestigated in trophozoites, early digestive cysts, reproductive cysts, and in developing resting cysts. Trophozoites possess numerous, minut e, spherical nuclei in interphase. In early digestive cysts the nuclei enlarge and the morphology of the nucleolus changes. The digestive cy sts develop into reproductive cysts. Karyokinesis takes place synchron ously. The spindle is intranuclear and acentrical. In metaphase, the c hromosomes are arranged in a distinct equatorial plate. The nuclear en velope remains intact at least until telophase. Shortly after karyokin esis the trophozoites leave the cysts. Cytokinesis regularly takes pla ce when the trophozoites invade cells of Oedogonium. Under unfavorable conditions the trophozoites as well as the digestive cysts are able t o form resting cysts. Nuclei of digestive cysts which begin to develop into resting cysts were found in the pachytene phase of meiosis, prov ed by synaptonemal complexes. Karyokinesis, probably the second meioti c division, was detected when the resting cyst was almost fully develo ped. From the results of our investigations, the vampyrellid filose am oebae can be regarded as sexual.