The Experts below are selected from a list of 84 Experts worldwide ranked by ideXlab platform
Nicole Lair - One of the best experts on this subject based on the ideXlab platform.
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the influence of autotrophic and heterotrophic foods on the demography of daphnia longispina under starved semi natural and enriched conditions
Journal of Plankton Research, 2000Co-Authors: Virginie Picard, Nicole LairAbstract:We tested the influence of different types of food on the fitness of Daphnia longispina during a period of poor resources by comparing the growth and reproduction of individuals fed on different diets. When Daphnia were under starvation conditions, both dissolved organic carbon and metabolic products enhanced bacterial growth, and the cladoceran produced 15 neonates and survived for the 55 days of experiment. In the natural water, the edible food consisted essentially of bacteria and heterotrophic flagellates, which enabled the cladoceran to grow and reproduce. In water enriched with Cryptomonas (an alga) or Chilomonas (a heterotrophic flagellate), the daphnid growth rates increased considerably from generation to generation, but later in the time course of the experi- ment with Chilomonas than with Cryptomonas. This alga enhanced the phosphorus:carbon ratio. The primiparous daphnids fed with Cryptomonas were smaller than those fed with the heterotrophic flagellate and enrichment with the heterotrophic flagellate also enhanced reproduction. In Lake Tazenat, when the algal biomass was insufficient to support the Daphnia life cycle, the heterotrophic organisms were an essential food source. When feeding essentially on bacteria, Daphnia has the capacity to grow and reproduce at very low food concentrations, and this is important in determining its fitness under competitive conditions.
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the effects of Chilomonas on the life history traits of 2pt daphnia longispina under semi natural conditions and the implications for competition in the plankton
Hydrobiologia, 2000Co-Authors: Nicole Lair, Virginie PicardAbstract:Assuming that heterotrophic flagellates (H.F.) can sustain cladoceran life cycles, particularly at periods of low food and high detritus conditions, the growth, reproduction and life span of Daphnia longispinawere studied under conditions of summer food limitation. They were fed both natural resources and natural food enriched with a culture of the colourless Chilomonas (ovoid cell, 8 × 25 μm). Four H.F. morphotypes occurred in the natural water and the first experiments with Daphnia, showed that the cladoceran would most easily ingest those of 5 μm–10 μm, while the addition of Chilomonas severely depressed the H.F. of 2 μm. The capability of this flagellate to ingest small H.F. was confirmed using fluorescent particles ranging from 0.94 to 3.95 μm. As a consequence, Daphnia could control the abundance of H.F., but also compete with the largest morphotypes. To study the influence of the H.F. on the life span of Daphnia, the cladoceran was acclimated for two generations, before the start of the experiments. In semi-natural conditions, constant temperature, without predators and fed natural water, the summer daphnids achieved smaller sizes, produced fewer offspring and lived for a shorter time than when Chilomonas was added to their diet. Despite the addition of 560 μg C l-1, this was not sufficient to enhance the Daphnia reproduction to the level of the spring population fed natural water. These results clearly illustrate that the heterotrophic flagellates contributed significantly to improving the reproduction and survival of the daphnids. They emphasise the importance of the microbial loop as a link to larger consumers, particularly when unpalatable or nutritionally inadequate algae are dominant, which is often so in lakes during summer.
Virginie Picard - One of the best experts on this subject based on the ideXlab platform.
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the influence of autotrophic and heterotrophic foods on the demography of daphnia longispina under starved semi natural and enriched conditions
Journal of Plankton Research, 2000Co-Authors: Virginie Picard, Nicole LairAbstract:We tested the influence of different types of food on the fitness of Daphnia longispina during a period of poor resources by comparing the growth and reproduction of individuals fed on different diets. When Daphnia were under starvation conditions, both dissolved organic carbon and metabolic products enhanced bacterial growth, and the cladoceran produced 15 neonates and survived for the 55 days of experiment. In the natural water, the edible food consisted essentially of bacteria and heterotrophic flagellates, which enabled the cladoceran to grow and reproduce. In water enriched with Cryptomonas (an alga) or Chilomonas (a heterotrophic flagellate), the daphnid growth rates increased considerably from generation to generation, but later in the time course of the experi- ment with Chilomonas than with Cryptomonas. This alga enhanced the phosphorus:carbon ratio. The primiparous daphnids fed with Cryptomonas were smaller than those fed with the heterotrophic flagellate and enrichment with the heterotrophic flagellate also enhanced reproduction. In Lake Tazenat, when the algal biomass was insufficient to support the Daphnia life cycle, the heterotrophic organisms were an essential food source. When feeding essentially on bacteria, Daphnia has the capacity to grow and reproduce at very low food concentrations, and this is important in determining its fitness under competitive conditions.
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the effects of Chilomonas on the life history traits of 2pt daphnia longispina under semi natural conditions and the implications for competition in the plankton
Hydrobiologia, 2000Co-Authors: Nicole Lair, Virginie PicardAbstract:Assuming that heterotrophic flagellates (H.F.) can sustain cladoceran life cycles, particularly at periods of low food and high detritus conditions, the growth, reproduction and life span of Daphnia longispinawere studied under conditions of summer food limitation. They were fed both natural resources and natural food enriched with a culture of the colourless Chilomonas (ovoid cell, 8 × 25 μm). Four H.F. morphotypes occurred in the natural water and the first experiments with Daphnia, showed that the cladoceran would most easily ingest those of 5 μm–10 μm, while the addition of Chilomonas severely depressed the H.F. of 2 μm. The capability of this flagellate to ingest small H.F. was confirmed using fluorescent particles ranging from 0.94 to 3.95 μm. As a consequence, Daphnia could control the abundance of H.F., but also compete with the largest morphotypes. To study the influence of the H.F. on the life span of Daphnia, the cladoceran was acclimated for two generations, before the start of the experiments. In semi-natural conditions, constant temperature, without predators and fed natural water, the summer daphnids achieved smaller sizes, produced fewer offspring and lived for a shorter time than when Chilomonas was added to their diet. Despite the addition of 560 μg C l-1, this was not sufficient to enhance the Daphnia reproduction to the level of the spring population fed natural water. These results clearly illustrate that the heterotrophic flagellates contributed significantly to improving the reproduction and survival of the daphnids. They emphasise the importance of the microbial loop as a link to larger consumers, particularly when unpalatable or nutritionally inadequate algae are dominant, which is often so in lakes during summer.
Gail E Ferris - One of the best experts on this subject based on the ideXlab platform.
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factors affecting the salinity tolerance of the freshwater cryptomonad Chilomonas paramecium
Journal of Eukaryotic Microbiology, 1992Co-Authors: Ravenna Ukeles, Gary H Wikfors, Gail E FerrisAbstract:. The capacity of the freshwater cryptomonad Chilomonas paramecium to develop a tolerance for seawater in the growth medium was investigated as part of a research program exploring potential microbial food sources for estuarine bivalve mollusks. By gradually increasing the percentage of estuarine seawater included in a freshwater culture medium over the course of 10 years, strains were obtained that tolerate from 16 to 32% seawater (highest salinity 10.5 ppt), achieving equivalent final densities with similar gross biochemical composition. However, after subculture in seawater-containing media for over 20 years, growth rates in more-saline media remained appreciably slower than in low-salinity media. Reduction of C. paramecium growth rate by seawater was found to be exacerbated in media with an initial pH of 3.5 as compared with pH 4.0–5.0, suggesting either a specific H+ effect upon metabolism of the medium carbon source (lactic acid) or a general cation effect upon nutrient uptake or cell metabolism. By contrast, depression of growth rates at high salinity was ameliorated by eliminating sodium-phosphate enrichments in growth media. This suggests that cations in the phosphate salt were contributing to cation-mediated growth inhibition. Results indicate a potential for C. paramecium, cultured in moderately saline media with no phosphate enrichments, to be used as a carbohydrate supplement for laboratory and hatchery feeding of estuarine bivalve mollusks.
Ravenna Ukeles - One of the best experts on this subject based on the ideXlab platform.
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factors affecting the salinity tolerance of the freshwater cryptomonad Chilomonas paramecium
Journal of Eukaryotic Microbiology, 1992Co-Authors: Ravenna Ukeles, Gary H Wikfors, Gail E FerrisAbstract:. The capacity of the freshwater cryptomonad Chilomonas paramecium to develop a tolerance for seawater in the growth medium was investigated as part of a research program exploring potential microbial food sources for estuarine bivalve mollusks. By gradually increasing the percentage of estuarine seawater included in a freshwater culture medium over the course of 10 years, strains were obtained that tolerate from 16 to 32% seawater (highest salinity 10.5 ppt), achieving equivalent final densities with similar gross biochemical composition. However, after subculture in seawater-containing media for over 20 years, growth rates in more-saline media remained appreciably slower than in low-salinity media. Reduction of C. paramecium growth rate by seawater was found to be exacerbated in media with an initial pH of 3.5 as compared with pH 4.0–5.0, suggesting either a specific H+ effect upon metabolism of the medium carbon source (lactic acid) or a general cation effect upon nutrient uptake or cell metabolism. By contrast, depression of growth rates at high salinity was ameliorated by eliminating sodium-phosphate enrichments in growth media. This suggests that cations in the phosphate salt were contributing to cation-mediated growth inhibition. Results indicate a potential for C. paramecium, cultured in moderately saline media with no phosphate enrichments, to be used as a carbohydrate supplement for laboratory and hatchery feeding of estuarine bivalve mollusks.
Gary H Wikfors - One of the best experts on this subject based on the ideXlab platform.
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factors affecting the salinity tolerance of the freshwater cryptomonad Chilomonas paramecium
Journal of Eukaryotic Microbiology, 1992Co-Authors: Ravenna Ukeles, Gary H Wikfors, Gail E FerrisAbstract:. The capacity of the freshwater cryptomonad Chilomonas paramecium to develop a tolerance for seawater in the growth medium was investigated as part of a research program exploring potential microbial food sources for estuarine bivalve mollusks. By gradually increasing the percentage of estuarine seawater included in a freshwater culture medium over the course of 10 years, strains were obtained that tolerate from 16 to 32% seawater (highest salinity 10.5 ppt), achieving equivalent final densities with similar gross biochemical composition. However, after subculture in seawater-containing media for over 20 years, growth rates in more-saline media remained appreciably slower than in low-salinity media. Reduction of C. paramecium growth rate by seawater was found to be exacerbated in media with an initial pH of 3.5 as compared with pH 4.0–5.0, suggesting either a specific H+ effect upon metabolism of the medium carbon source (lactic acid) or a general cation effect upon nutrient uptake or cell metabolism. By contrast, depression of growth rates at high salinity was ameliorated by eliminating sodium-phosphate enrichments in growth media. This suggests that cations in the phosphate salt were contributing to cation-mediated growth inhibition. Results indicate a potential for C. paramecium, cultured in moderately saline media with no phosphate enrichments, to be used as a carbohydrate supplement for laboratory and hatchery feeding of estuarine bivalve mollusks.