Premium
Study of Dientamoeba fragilis Jepps & Dobell I. Electronmicroscopic Observations of the Binucleate Stages II. Taxonomic Position and Revision of the Genus *
Author(s) -
CAMP RUSSELL R.,
MATTERN CARL F. T.,
HONIGBERG B. M.
Publication year - 1974
Publication title -
the journal of protozoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 0022-3921
DOI - 10.1111/j.1550-7408.1974.tb03619.x
Subject(s) - biology , microtubule , centriole , nucleus , telophase , golgi apparatus , organelle , flagellum , microbiology and biotechnology , anatomy , endoplasmic reticulum , metaphase , genetics , chromosome , gene
SYNOPSIS Light‐ and electronmicroscopic observations on Dientamoeba fragilis strain A (Bi) 1 dealing primarily with the binucleate (arrested telophase) stages, predominant in all populations, revealed the microtubular nature of the extranuclear spindle which extends between the 2 polar complexes each adjacent to one of the nuclei. The spindle microtubules originate in paired, nonperiodic structures apparently homologous to the “atractophores” described from hypermastigotes. To the external surface of the atractophores are applied periodic elements, which extend laterally as the parabasal filaments. Extensive Golgi complexes overlie the filaments, these structures corresponding to the components of the parabasal apparatus known from trichomonads and hypermastigotes. The 2‐layered structures, consisting of the atractophores and periodic layers, together with the proximal parts of the Golgi complex and the spindle microtubules constitute the polar complex. No kinetosome‐ or centriole‐like organelles have been found in the polar complexes or elsewhere in the organism. The extranuclear spindle is composed of 2 microtubule bundles, each with ∼30‐40 microtubules. One of the bundles always appears at some distance from the nucleus; the other is juxtanuclear and is seen often to course within a groove of the nuclear envelope. A 3rd bundle of ∼35‐45 microtubules is seen on occasion to arise from the atractophores and to pass toward the nucleus at a wide angle to the other parts of the spindle. In some instances these microtubules traverse the nucleus within channels delimited by the nuclear envelope. The double‐layered nuclear envelope contains numerous pores. Two morphologic types of rounded inclusions, one microbody‐like, and the other with a more electron‐translucent matrix, as well as digestive vacuoles containing rice starch, bacteria, and/or myelin configurations are distributed in the cytoplasm, which abounds also in glycogen granules. The fine structure of Dientamoeba is compared with those of trichomonads and of Entamoeba spp. The taxonomic position of Dientamoeba is discussed and emended; in view of its affinities, this genus is placed among trichomonads in the family Dientamoebidae Grassé, emend.