Structure and development of Pelomyxa gruberi sp. n. (Peloflagellatea, Pelobiontida)

• Main Authors: Er O. Frolov, Andrew V. Goodkov, Ludmila V. Chystjakova, Sergei O. Skarlato
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: The syst; Northwest Russia
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.564.7254; http://protistology.ifmo.ru/num4_3/frolov.pdf

The general morphology, ultrastructure, and development of a new pelobiont protist, Pelomyxa gruberi, have been described. The entire life cycle of this eukaryotic microbe involves an alteration of uni and multinucleate stages and is commonly completed within a year. Reproduction occurs by plasmotomy of multinucleate amoebae: they form division rosettes or divide unequally. Various surface parts of this slowlymoving organism characteristically form fingershaped hyaline protrusions. Besides, during the directed monopodial movement, a broad zone of hyaline cytoplasm with slender fingershaped hyaline protrusions is formed at the anterior part of the cell. In multinucleate stages up to 16 or even 32 nuclei of a vesicular type may be counted. Individuals with the highest numbers of nuclei were reported from the southernmost part of the investigated area: the NorthWest Russia. Each nucleus of all life cycle stages is surrounded with microtubules. The structure of the flagellar apparatus differs in individuals of different age. Small uninucleate forms have considerably fewer flagella per cell than do larger or multinucleate amoebae but these may have aflagellated basal bodies submerged into the cytoplasm. In young individuals, undulipodia, where available, emerge from a characteristic flagellar pocket or tunnel. The basal bodies and associated rootlet microtubular derivatives (one radial and one basal) are organized similarly at all life cycle stages. There is a thinwalled cylinder in the flagellar transition zone, and an electrondense column above that zone. In the separate nonmotile undulipodia the arrangement of axoneme microtubules deviates from the typical 9+2 eukaryotic pattern. In the cytoplasm of P. gruberi two types of rodshaped endocytobionts are present: (1) large bacteria with a pronounced longitudinal cleft, and (2) smaller methanogenlike bacteria.