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CELL DIVISION IN GLOEOTILOPSIS PLANCTONICA , A NEWLY IDENTIFIED ULVOPHYCEAN ALGA (CHLOROPHYTA) STUDIED BY FREEZE FIXATION AND FREEZE SUBSTITUTION 1
Author(s) -
Sluiman Hans J.
Publication year - 1991
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.1991.00291.x
Subject(s) - biology , basal body , mitosis , golgi apparatus , cell division , interphase , prophase , centriole , microbiology and biotechnology , ultrastructure , cleavage furrow , microtubule , cytokinesis , botany , flagellum , endoplasmic reticulum , meiosis , cell , genetics , gene
Gloeotilopsis planctonica Iyengar & Philipose, a soil isolate, was cultured for the first time since its description in 1956. Cell division was investigated ultrastructurally by using rapid freeze fixation and freeze substitution. Vegetative interphase cells contain a persisting basal apparatus (centrioles) in which the absolute configuration of the basal body pair is identical to that in ulvophycean flagellated cells. Basal apparatus replication and segregation occurs shortly before prophase. Also before mitosis, a shallow plasma membrane indentation is formed, subtended by 2–3 cortical microtubules, in the forthcoming division plane. Daughter basal body pairs are located lateral to the mitotic spindle poles. A Golgi stack occupies each polar position of the mitotic spindle. During mitosis, which is structurally identical to that described previously for members of the Ulotrichales sensu Sluiman (Ulvophyceae), an extensive network of tubular membranes (trans Golgi reticulum, TGR) develops from each polar Golgi stack to the incipient cleavage furrow. A microtubular system, possibly organized by the basal apparatus, is associated with both the TGR and the cytokinetic septum. The TGR appears to be involved in the further development of the furrow after mitosis is completed. I conclude on the basis of this ultrastructural study that the genus Gloeotilopsis , which includes G. planctonica Iyengar & Philipose (type species) and G. sterilis Deason, should be classified in the Ulotrichales sensu Sluiman, class Ulvophyceae.