The Experts below are selected from a list of 78 Experts worldwide ranked by ideXlab platform
Ruth L. Willey - One of the best experts on this subject based on the ideXlab platform.
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the reservoir cytoskeleton and a possible cytostomal homologue in Colacium euglenophyceae 1
Journal of Phycology, 2004Co-Authors: Ruth L. Willey, Ronald G. WibelAbstract:The reservoir cytoskeleton of Colacium Ehrenberg is formed of three bands of microtubules. The microtubules of the dorsal band (DMT) become doublets and are continuous with the longitudinal microtubules of the canal and, therefore, of the pellicle. A band of para-reservoir microtubules (PMT) acts as a linkage between the edges of the dorsal band at the formation of the canal. The third band of microtubules (MTR), more ventral, branches away from the reservoir-canal transition region and forms a supportive band for a pocket formed from the reservoir membrane. The outer part of the pocket membrane is closely invested with a fibrillar mesh. The pocket of Colacium, a green euglenoid, resembles structurally the cytopharynx of the colorless phagotrophic euglenoids, Isonema papillatum and the bodonid flagellates. The homologies support the hypothesis of euglenoid derivation from the kinetoplastid flagellates.
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colonization and reproduction of the epibiotic flagellate Colacium vesiculosum euglenophyceae on daphnia pulex1
Journal of Phycology, 1996Co-Authors: Rowaya S Aldhaheri, Ruth L. WilleyAbstract:The epibiotic flagellate Colacium vesiculosum Pringsheim attaches to planktonic species of Daphnia in freshwater habitats. Previous studies found that prevalence (percentage of substrate organisms carrying attached epibionts) and intensity (number of attached epibionts on a given substrate organism) are low early in the Daphnia intermolt period and are high late in the intermolt period. We tested the hypothesis that increases of Colacium cells attached to Daphnia occur both by rapid initial and continuous colonization and by cell reproduction. Epibiont prevalence and intensities were determined at successive intermolt stages of Daphnia pulex Leydig collected from freshwater ponds in Colorado. Colonization was continuous throughout the intermolt period and was most important to epibiont population increase at the beginning of the intermolt period. Cell division was the major contributor to epibiont increase at the end of the intermolt period.
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Planktivore effects on zooplankton epibiont communities: Epibiont pigmentation effects
Limnology and Oceanography, 1993Co-Authors: Ruth L. Willey, Robert B. Willey, Stephen T. ThrelkeldAbstract:We observed the development of epibiont communities on freshwater crustacean zooplankton from 12 July–31 August 1991 in three ponds: one with planktivorous fish, a second with planktivorous larval salamanders, and a third with planktivorous fish added midway through the sampling period. Prevalence, on zooplankton, of pigmented euglenoid epibionts (Colacium vesiculosum), alone and with unpigmented peritrich ciliates (Vorticella campanula and Epistylis sp.), was significantly reduced by the addition of planktivorous fish in the third pond, while the prevalence of peritrich ciliates alone was not. Neither of the ponds with unaltered planktivore regimes showed a similar pattern of change in prevalence of pigmented and unpigmented epibionts on zooplankton. The relative loss of pigmented euglenoid epibionts, after planktivore addition, suggests that epibiont color or contrast may increase the susceptibility of their substrate organisms to planktivores.
Gérard Lacroix - One of the best experts on this subject based on the ideXlab platform.
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Control mechanisms of photosynthetic epibionts on zooplankton: an experimental approach
Ecosphere, 2015Co-Authors: Andrea Bertolo, Marco A. Rodríguez, Gérard LacroixAbstract:Several top-down and bottom-up forces have been put forward to explain variable infestation rates of zooplankton by epibionts. Among top-down forces, fish predation affects epibiont prevalence on zooplanktonic organisms, either by eliminating more conspicuous, heavily burdened individuals, or by reducing population size of zooplankton hosts, with consequences for substrate availability for epibionts. However, detailed experimental-based information on the effects of top-down forces is still lacking. Among bottom-up forces, light can potentially control populations of photosynthetic epibionts. Therefore, both changes in light penetration in the water column and the vertical position of hosts in the water column could affect the photic conditions in which epibionts live and could thus control their population growth. We tested experimentally the hypothesis that both light limitation and fish predation affect epibiont burden on zooplankton. Moreover, we also tested the hypothesis that zooplanktivorous fish affect the prevalence and burden of the epibiotic alga Colacium sp. (Euglenida) on zooplankton not only by direct predation, but also by affecting the vertical distribution of zooplankton. We analyzed Colacium burden on two zooplankton genera that responded differently to the presence of zooplanktivorous fish by altering their daytime vertical distributions, thus exposing photosynthetic epibionts to different light conditions. Colacium burden on the two zooplankton genera was also compared between enclosures with different degrees of light limitation. Our results suggest that (1) ambient light limitation has the potential to reduce the burden of photosynthetic epibionts on zooplankton in natural conditions, and (2) zooplankton behavior (e.g., daytime refuge use to escape fish predation) can reduce the burden by exposing photosynthetic epibionts to suboptimal light conditions.
Ronald G. Wibel - One of the best experts on this subject based on the ideXlab platform.
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the reservoir cytoskeleton and a possible cytostomal homologue in Colacium euglenophyceae 1
Journal of Phycology, 2004Co-Authors: Ruth L. Willey, Ronald G. WibelAbstract:The reservoir cytoskeleton of Colacium Ehrenberg is formed of three bands of microtubules. The microtubules of the dorsal band (DMT) become doublets and are continuous with the longitudinal microtubules of the canal and, therefore, of the pellicle. A band of para-reservoir microtubules (PMT) acts as a linkage between the edges of the dorsal band at the formation of the canal. The third band of microtubules (MTR), more ventral, branches away from the reservoir-canal transition region and forms a supportive band for a pocket formed from the reservoir membrane. The outer part of the pocket membrane is closely invested with a fibrillar mesh. The pocket of Colacium, a green euglenoid, resembles structurally the cytopharynx of the colorless phagotrophic euglenoids, Isonema papillatum and the bodonid flagellates. The homologies support the hypothesis of euglenoid derivation from the kinetoplastid flagellates.
Mineo Iseki - One of the best experts on this subject based on the ideXlab platform.
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The origin of photoactivated adenylyl cyclase (PAC), the Euglena blue-light receptor: Phylogenetic analysis of orthologues of PAC subunits from several euglenoids and trypanosome-type adenylyl cyclases from Euglena gracilis
Photochemical and Photobiological Sciences, 2004Co-Authors: Yoshiko Koumura, Shinya Yoshikawa, Masakatsu Watanabe, Takeshi Suzuki, Mineo IsekiAbstract:Photoactivated adenylyl cyclase (PAC) is the blue-light receptor flavoprotein recently identified as a photoreceptor for photoavoidance of the unicellular flagellate, Euglena gracilis. To gain an insight into the evolution of this unique protein, similar sequences were searched for in several euglenoids by reverse transcriptase-polymerase chain reation (RT-PCR) using degenerate primers. Two similar transcripts were detected in each of the four phototrophic euglenoids, Euglena stellata, Colacium sideropus, Eutreptia viridis, Eutreptiella gymnastica, and in an osmotrophic (i.e., obtaining nutrients by absorption) one, Khawkinea quartana, but not in a phagotrophic euglenoid, Petalomonas cantuscygni. Each of them seemed to be orthologous to PACα and PACβ, respectively, and had the same domain structure as PAC subunits each of which is composed of two flavin binding domains, F1 and F2, each followed by an adenylyl cyclase catalytic domain, C1 and C2, respectively. This fact implies that they constitute a functional photoactivated adenylyl cyclase like PAC. Phylogenetic analysis of the adenylyl cyclase catalytic domains revealed that they belong to a bacterial cluster, not to a trypanosomal one. In addition, two trypanosome-type adenylyl cyclases were discovered in E. gracilis. In contrast to PAC, deduced amino acid sequences of the trypanosome-type adenylyl cyclases indicated that they are integral membrane proteins with a membrane spanning region at the midpoint of them, followed by an adenylyl cyclase catalytic domain which seems cytoplasmic. Overall, we propose that PAC might have been transferred to euglenoids on the occasion of secondary endosymbiosis.
Andrea Bertolo - One of the best experts on this subject based on the ideXlab platform.
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Control mechanisms of photosynthetic epibionts on zooplankton: an experimental approach
Ecosphere, 2015Co-Authors: Andrea Bertolo, Marco A. Rodríguez, Gérard LacroixAbstract:Several top-down and bottom-up forces have been put forward to explain variable infestation rates of zooplankton by epibionts. Among top-down forces, fish predation affects epibiont prevalence on zooplanktonic organisms, either by eliminating more conspicuous, heavily burdened individuals, or by reducing population size of zooplankton hosts, with consequences for substrate availability for epibionts. However, detailed experimental-based information on the effects of top-down forces is still lacking. Among bottom-up forces, light can potentially control populations of photosynthetic epibionts. Therefore, both changes in light penetration in the water column and the vertical position of hosts in the water column could affect the photic conditions in which epibionts live and could thus control their population growth. We tested experimentally the hypothesis that both light limitation and fish predation affect epibiont burden on zooplankton. Moreover, we also tested the hypothesis that zooplanktivorous fish affect the prevalence and burden of the epibiotic alga Colacium sp. (Euglenida) on zooplankton not only by direct predation, but also by affecting the vertical distribution of zooplankton. We analyzed Colacium burden on two zooplankton genera that responded differently to the presence of zooplanktivorous fish by altering their daytime vertical distributions, thus exposing photosynthetic epibionts to different light conditions. Colacium burden on the two zooplankton genera was also compared between enclosures with different degrees of light limitation. Our results suggest that (1) ambient light limitation has the potential to reduce the burden of photosynthetic epibionts on zooplankton in natural conditions, and (2) zooplankton behavior (e.g., daytime refuge use to escape fish predation) can reduce the burden by exposing photosynthetic epibionts to suboptimal light conditions.