Ref ID : 4698
S.A. Karpoff and B.F. Zhukov; Ultrastructure and Taxonomic Position of Apusomonas proboscidea Alexeieff. Arch.Protistenk 131:13-26, 1986
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The ultrastructure and taxonomic position of the colourless flagellate Apusomonas proboscidea Alexeieff, a member of coprophilic and freshwater faunas, has been studied for the first time. The following features have been revealed as a result of examination of ultra-thin sections. Nearly all the body of the flagellate is covered by a thick five-layered membrane. An exception is the ventral groove lined with a unit membrane. In the groove there are two flagella, the anterior and the posterior, both of whiplash type. Their kinetosomes are located in the distal part of the proboscis. Three bands of microtubules, emerging from the basal apparatus of the flagella, pass inside the proximal part of the proboscis. One of them looks like a multilayered structure. There is an electron-dense rodlike body at the base of the proboscis. The only dictyosome of the Golgi apparatus lies close to it. The mitochondria contain tubular cristae. The nucleus belongs to the vesicular type, with a well pronounced nucleolus. The cytoplasm is clearly differentiated into endoplasm and a denser ectoplasm. Ingestion of food (bacteria) occurs in the rear part of the ventral groove (the ventral pouch). The unique pattern of the cell structure of A. proboscidea does not allow to include it into any of the known groups of flagellates. According to some features, this species is compared with euglenoid algae, the bicosoecids, and with some other flagellates of unclear taxonomic position.