THE INFLUENCE OF THE MODE OF NUTRITION ON THE DIGESTIVE SYSTEM OF <i>OCHROMONAS MALHAMENSIS </i>

Stoltze, H. J.; Lui, Nan S. T.; Anderson, O. Roger; Roels, Oswald A.

doi:10.1083/jcb.43.3.396

Cited by 26 publications

(8 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The planktonic flagellate Ochromonas, the subject of the experiments reported here, can take up dissolved organic carbon (DOC) compounds osmotrophically (Stoltze et al, 1969;Holen & Boraas, 1995), is an important consumer of bacteria (Daley, Morris & Brown, 1973;Zubkov et al, 2001;Schmidtke et al, 2006) and can also prey on small eukaryotic phytoplankton (Boraas, Seale & Boxhorn, 1998). Thus, Ochromonas is a consummate generalist, with an ability to garner resources and energy via a striking variety of trophic pathways, but it is an inferior competitor against autotrophic and heterotrophic specialists.…”

Section: Introductionmentioning

confidence: 99%

Mixotrophy and the toxicity of Ochromonas in pelagic food webs

2012

View full text Add to dashboard Cite

Summary 1. Toxic compounds produced by many phytoplankton taxa are known to have negative effects on competitors (allelopathy), anti‐predatory effects on grazers (mortality or impaired reproduction) or both. Although mixotrophs of the genus Ochromonas are known to be toxic to zooplankton, it has often been assumed in studies of plankton community processes that all flagellates in the size range of this taxon are edible to typical zooplankton grazers (i.e. cells ≤30 μm for Daphnia, ≤6 μm for rotifers). 2. We explored the toxicity of a species of Ochromonas to other planktonic taxa, including its competitors (two species of phytoplankton and protists) and consumers (two species of zooplankton). To test if mode of nutrition by this mixotroph influences its toxicity to other taxa, we exposed each test species to Ochromonas cultured in chemostats under four different nutritional regimes: osmotrophy (labile dissolved organic carbon) and phagotrophy (bacterial prey) in both light and dark conditions (i.e. with or without photosynthesis). 3. Filtrate from osmotrophically fed Ochromonas had a significant negative effect on the population growth rate of two obligate phototrophic phytoplankton, Cryptomonasozolini and Chlamydomonas reinhardtii. The protists Tetrahymena tetrahymena and Paramecium aurelia were also negatively affected by Ochromonas filtrate. Ochromonas cells were toxic to both the rotifer Brachionus calicyflorus and the cladoceran Daphnia pulicaria, with the toxic effects significantly more severe when fed at high cell densities (75 000 cells mL−1) than at low densities (7500 cells mL−1). Ochromonas cultured osmotrophically in the light was more toxic to the Daphnia than cells cultured under other conditions. In contrast, Ochromonas from all nutritional conditions was equally highly toxic to Brachionus. 4. Our findings support the view that Ochromonas can be toxic to other components of the food web with which it interacts. It is especially toxic to zooplankton that directly consume it, although the effect depends upon Ochromonas cell density and whether or not a good food source is simultaneously present. Our results call into question the common practice of pooling flagellates into a single ‘functional group’ included in an ‘edible phytoplankton’ category of cells <30 μm in diameter.

show abstract

Section: Introductionmentioning

confidence: 99%

Mixotrophy and the toxicity of Ochromonas in pelagic food webs

2012

View full text Add to dashboard Cite

show abstract

“…Hence, clearance rates on other viruses might provide estimates much higher (up to 100 %) than those reported. Furthermore, several authors (Muller et al 1965, Stolze et al 1969, Wetzel & Korn 1969, Dubowsky 1974 have shown that the digestive system in a variety of protozoa is activated upon the formation of particle-containing vacuoles. The results we obtained using viruses that were labelled with an FITC-conjugated antibody also suggest that digestion of food particles is rapidly initiated.…”

Section: Ingestion and Digestion Rates Of Virusesmentioning

confidence: 99%

Grazing by marine nanofiagellates on viruses and virus-sized particles: ingestion and digestion

Gonzalez¹,

Suttle²

1993

Mar. Ecol. Prog. Ser.

268

217

View full text Add to dashboard Cite

We examined grazing of marine viruses and bacteria by natural assemblages and cultures of phagotrophic nanoflagellates. Ingestion rates were determined using fluorescently labelled viruses (FLVs) and bacteria (FLB), and 50 or 500 nm diameter fluorescent microspheres (FMs). Calculated clearance rates of viruses by natural nanoflagellate assemblages were about 4 % of those for bacter~a when the bacteria and viruses were present at natural concentrations. Different viruses were ingested at different rates w~t h the smallest virus being ingested at the slowest rate. Further, we found differences in digestion times for the same flagellates grazing on different vlruses and for different flagellate assemblages grazing on the same viruses. FMs of 50 nm diameter were used as a control for egestion of undlgested particles. As rates of digestion were greater than those for ingestion both processes would occur simultaneously; hence, our estimates of grazing rate are likely conservative. Ingestion rates were positively correlated with the concentration of 50 nm FMs. Discriminat~on agalnst 50 nm FMs in favor of FLVs was also observed. Our calculations suggest that vlruses may be of nutritional significance for phagotrophic flagellates. When there are lob bacteria ml-l and 10' to 10' vvlruses ml-l, viruses may represent 0.2 to 9 % of the carbon, 0.3 to 14 ' % of the nitrogen and 0.6 to 28 "/a of the phosphorus that the flagellates obtain from ingestion of bacteria. This study demonstrates that both natural assemblages and cultures of phagotrophic nanoflagellates consume and digest a variety of marine vlruses, thereby deriving nutritional benefit and serving as a natural sink for marine viral particles. In addition, these results imply that some nanoflagellates are likely capable of consuming a wide spectrum of organlc particles in the colloidal size range.

show abstract

“…Barlow and Triemer (1986) observed acid phosphatase activity in the Golgi cisternae and ER of the heterotrophic dinoflagellate, C. cohnii. Acid phosphatase activity has also been detected in lysosome-like structures, the ER, and the Golgi complex of many non-dinoflagellate protists (Sommer and Blum, 1965;Elliott and Clemmons, 1966;Dembitzer, 1968;Stoltze et al, 1969;McAlpine, 1970;Brooker, 1971;Gomez et al, 1974;Langreth and Balber, 1975;Ryter and Bowers, 1976;Grab et al, 1997). Smaller ELF-97 deposits occurred throughout the cytoplasm in some P. shumwayae cells.…”

Section: Discussionmentioning

confidence: 94%