Light is a crucial signal for zoosporogenesis and gametogenesis in some green microalgae

Abstract

Patterns of reproduction were investigated in some microalgal species of Chlorophyceae (Botryosphaerella sudetica, Neochloris aquatica, Neochloris vigensis, Bracteacoccus minor). Under continuous light, the microalgae reproduced asexually producing autospores. However, appropriate manipulation of external conditions led to a change in the reproduction pattern towards production of zoospores or gametes. Production of zoospores and gametes was inhibited by light; motile cells emerged when microalgae were cultivated in darkness. The period of dark treatment necessary for zoosporogenesis or gametogenesis differed substantially among species that were tested. Sexual reproduction was observed in Neochloris vigensis and Bracteacoccus minor, whose generative life cycle had not been previously reported. The morphology of motile cells, the mode of sexual reproduction, and the efficiency of both the production of motile stages and mating events, were investigated. In order to gain detailed insights into patterns of reproduction, Botryosphaerella sudetica was selected for investigation under different light treatments. Nonactinic red light applied in the early phase of dark cultivation (up to 2 h) suppressed both zoosporogenesis and gametogenesis. However, after a 3-h dark pre-treatment, red light treatment had no effect on zoosporogenesis or gametogenesis. In contrast, nonactinic blue light did not block zoosporogenesis or gametogenesis, regardless of the time of treatment. The possible role of a redlight photoreceptor in zoosporogenesis and gametogenesis is discussed.

Culex quinquefasciatus larvae development arrested when fed on Neochloris aquatica

“…While searching for optimal culture conditions, we obtained autospores in N. aquatica cultures exposed to constant light, as well as in photoperiod conditions, where division cells and differences in size were observed in transitions of constant light to darkness, and photoperiod to darkness, respectively. Detected morphologies are also seen in other Chlorophyceae [43], and as previously described by Přibyl [29], no motile cells were found in dark conditions due to their asexual reproduction by autospores. Many microalga metabolites have been described so far, most of them allelochemicals [13,14], which give them relevant advantages.…”

“…As during the isolation of the alga, different morphotypes were detected according to the culture conditions, and the objective was to recreate the shape detected in the field samples. For that, the microalga was incubated under different light conditions and constant temperature according to Přibyl [29]. Briefly, overnight culture (OD 750 0.4) was divided in three equal parts, two of them were grown under continuous light, while the other one was cultivated in photoperiod condition (16:8 h light: dark cycles).…”

Differential Responses to UV-A Stress Recorded in Carotenogenic Microalgae Haematococcus rubicundus, Bracteacoccus aggregatus, and Deasonia sp.

“…Light intensity and spectral quality play a significant role in both sporogenesis and gametogenesis in green algae. Short-wavelength (blue) PAR radiation is favorable for massive formation of flagellated cells, whereas long-wavelength (red) PAR blocks it [ 26 ]. In the macrophyte Bryopsis plumosa (Ulvophyceae), a positive effect of UV-A on motile stages production has been reported [ 27 ].…”

“…Light microscopic observations of cells is important part of works with unicellular algae (microalgae) [ 11 , 15 ]. The approaches attempted to study algal life cycle also have been reported [ 24 , 26 , 27 ]. In the macrophytic red algae Mastocarpus stellatus and Chondrus crispus an effect of UV-A and UV-B on germination and carpospores viability, as well as on PSA was shown [ 24 ].…”

Long-Term Experiment on Physiological Responses to Synergetic Effects of Ocean Acidification and Photoperiod in the Antarctic Sea Ice Algae Chlamydomonas sp. ICE-L

“…Light is also critical to the pattern of reproduction in some micoralgal species. Continuous light leads to asexual reproduction and production of antospores, while darkness can induce zoosporogenesis or gemetogenesis . A recent study of the model green alga Chlamydomonas (Chlorophyta) found that it could grow heterotrophically in the dark on medium supplemented with acetate, and there is some genetic variation in the survival process.…”