Abstract
Summary During routine ultrastructural research on the morphological features of Desmatractum bipyramidatum ( Chodat ) Pascher (1930), thirteen cells were selected by light microscope in a flat embedded heterogenous sample of algae from a Dutch moorland pool complex ( Kouwets 1980) and sectioned for transmission electron microscopy (TEM) ( Reymond & Kouwets 1981). In addition to the presence of the usual organelles, several bacteria-like structures assumed to be endosymbionts were found in three cells and their spatial position was reconstructed through serial sections. None of the symbionts observed in the cytoplasm of the three cells seemed to be preferentially related to specific organelles. The most interesting of these algal cells (about 5.6 μm in diameter), contained three endosymbionts; two of them were very long (about 26 μm and 40 μm respectively, with a diameter of about 0.3 μm) and formed obvious intracytoplasmic loops mostly situated underneath the cell membrane. They were lying freely in the cytoplasm surrounded by an electron-translucent area, showing similarities with the organisms shown by Kochert & Olson (1970) in Volvox or Nozaki et al. (1989) in Pleodorina. Two other cells (about 7 μm in diameter) contained endosymbionts with characteristic rod-shaped bacterial structures (about 0.7–1.3 μm long and 0.6 μm in diameter). They were lying scattered in the cytoplasm with no surrounding electron-translucent area. One of these contained seventeen endosymbionts and the other about three. Sporadically algologists report the presence of bacteria-like endosymbionts in algae (i.e., Kochert & Olson 1970; Turner & Friedmann 1974; Heywood 1978; Margulis et al. 1978; Nozaki et al. 1989). However, the very long coiled endosymbionts found in one cell of D. bipyramidatum seem very unusual, and to our knowledge, such a morphology has not previously been described. The fact that 3 of 13 cells revealed the presence of endosymbionts lead us to think that an important part of the population is naturally involved in this symbiosis. This species of alga is unfortunately never abundant in its natural environment. Until now, despite some successful but brief attempts at establishing cultures ( Kouwets , pers. comm.) this material from Holland did not permit further investigations with TEM or other methods. Cells of natural populations of D. indutum, D. spryii and D. delicatissimum have also been investigated with TEM ( Reymond & Kouwets 1984), but up to now no endosymbionts have been reported for these species.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call