Palmelloids formation in Chlamydomonas reinhardtii : defence against rotifer predators?

Abstract

The green alga Chlamydomonas reinhardtii usually occurs in cultures as single, biflagellated cells. However, C. reinhardtii is known for its ability to form gelatinous and palmelloid stages that arise as a result of an interaction with its environment. Exponentially growing unicellular C. reinhardtii formed palmelloid colonies rapidly within 25 h when cultured together with their enemy the rotifer Brachionus calyciflorus. Consequences of palmelloid formation for population dynamics of both C. reinhardtii and B. calyciflorus were examined in continuous flow systems. Palmelloids were only formed in a one-stage system where B. calyciflorus grazers and C. reinhardtii prey were cultured together, but not in a two-stage system in which mainly unicellular C. reinhardtii was pumped into a rotifer culture placed in darkness. The rotifer abundance was lower and the algal biomass higher in the one-stage system compared to the grazing unit of the two-stage system. Inasmuch as palmelloids seemed to give C. reinhardtii cells resistance to grazing, we suggest that at least one of the reasons why C. reinhardtii is capable of forming palmelloids is to cope with herbivory. desmus and Chlamydomonas formed colonies in the presence of herbivorous zooplankton. Divisive colony formation in Scenedesmus has been studied intensively the last decade and has become a paradigm of induced defences in phytoplankton (Hessen & Van Donk 1993, Lampert et al. 1994, Lürling 1998, von Elert & Franck 1999, van Holthoon et al. 2003. In contrast, until now no studies have been undertaken to verify the second part of the findings of Mikheeva & Kruchkova (1980) and to examine the potential of grazer-induced phenotypic plasticity in Chlamydomonas. The first objective of the current study was to test the hypothesis that zooplankton (the rotifer Brachionus calyciflorus) can induce palmelloid formation in Chlamydomonas as has been found for Scenedesmus .Forming colonies made Scenedesmus more difficult to eat by zooplankton and reduced the enemy's population growth (Hessen & Van Donk 1993, Lürling & Van Donk 1996. In those studies, defended algae were fed at a constant concentration to the consumers and their effects on zooplankton were examined. However, to improve our understanding of the dynamics of induced defences, an assessment of the population consequences for both grazer and algal prey is required (Tollrian & Harvell 1999). Simulations with a predator-prey model for algae and rotifers (Brachionus) predicted that induced defences in algae stabilised the population dynamics of this system; increased algal biomass and decreased rotifer biomass (Vos et al. 2004). The second objective of the current study was to test these modelling predictions experimentally for continuous flow systems with C. reinhardtii as prey and B. calyciflorus as predators. Formation of palmelloid colonies in C. reinhardtii is expected to occur in a onestage system where B. calyciflorus grazers and C. reinhardtii prey are cultured together, but not in a two-stage system in which un...

Evaluation of several end-of-pipe measures proposed to control cyanobacteria

“…Such intensities are much lower than the intensities applied in laboratory studies (mean ± 1 SD: ). M. aeruginosa was grown in 100-mL Erlenmeyer flasks containing 50 mL of autoclaved WC medium (Lürling and Beekman 2006) that were placed in a Gallenkamp ORBI-SAFE Netwise Orbital Incubator at 20°C, in 60 rpm and in a 18:6-h light:dark rhythm that was programmed to gradually increase light intensity to a maximum of 130 lmol quanta m -2 s -1 and subsequently decreased again to darkness, which resulted in a daily average light intensity of *57 lmol photons m -2 s -1…”

Effects of Commercially Available Ultrasound on the Zooplankton Grazer Daphnia and Consequent Water Greening in Laboratory Experiments

“…Daphnia was cultured at 20 °C in 1 L jars containing 800 mL artificial RT-medium [14]. Three times a week Daphnia cultures received about 4 mg C·L on modified WC (Woods Hole modified CHU10) -medium [15]. Each three-four weeks about 20 adult specimens from stock cultures were transferred to clean jars with fresh medium.…”

Culturing of Autoflocculating Microalgal Consortium in Continuous Raceway Pond Reactor

“…Cell division can take place within this mucilage floc, thereby restricting separation of the cells. Grazing organisms present in the batch system remove free suspended cells in the system [19] [20]. Small grazers, such as ciliates and rotifers, are unable to penetrate the mucilaginous cover of the floc for feeding on the cells.…”