Search results for "Rotifer"

Demographic parameters of Brachionus calyciflorus Pallas (Rotifers) exposed to sublethal endosulfan concentrations

1991

The effects of sublethal levels of endosulfan (0, 1, 1.5, 2.5 and 3.3 mg 1−1) on the demography of the rotifer Brachionus calyciorus were studied. Life expectancy at birth (e o), net reproductive rate (Ro), generation time (T) and intrinsic rate of natural increase (r) were significant differentes between blank controls and controls with acetone. The effective endosulfan concentration at which a given parameter value was reduced to 50% of the controls (EC50) was calculated for life expectancy.

Protein patterns in rotifers: the timing of aging

1989

Single rotifer individuals have been characterized biochemically to obtain a fingerprint of their physiological state using a modified ultrasensitive silver-stain procedure to detect total proteins in polyacrylamide gels. Patterns are completely uniform for young isogenic individuals raised in the same culture, but they start to change when these individuals reach a certain age. This age is close to the mean lifespan and to both the cessation of body growth and reproduction. Variability is greatest among individuals of the same chronological age, thus the rate of aging is different even among individuals having identical genotypes and experiencing the same environment.

Application of Toxkit microbiotests for toxicity assessment in soil and compost

2004

The potential of Toxkit microbiotests to detect and analyze pollution in agricultural soil and the quality of compost was studied. The toxicity tests used included seed germination biotests using cress salad (Lepidum sativum L.), tomato (Lycopersicum esculentum L.), and cucumber (Cucumis sativus L.), and the Toxkit microbiotests included those with microalgae (Selenastrum capricornutum), protozoa (Tetrahymena thermophila), crustaceans (Daphnia magna, Thamnocephalus platyurus, and Heterocypris incongruens), and rotifers (Brachionus calyciflorus). Experiments on compost were undertaken in a modified solid-state fermentation system (SSF) and under field conditions (in a windrow). To promote th…

Acute toxicity of toluene, hexane, xylene, and benzene to the rotifers Brachionus calyciflorus and Brachionus plicatilis.

1992

A large number of studies on the biological effects of oil pollution in the aquatic environment deal with the effects of whole crude or refined oils or their water-soluble fractions. However, low boiling, aromatic hydrocarbons, which are probably the most toxic constituents of oil, have until now not been examined in sufficient detail. Toluene, benzene and xylene, constitute a major component of various oils. They may be readily lost by weathering but are toxic in waters that are relatively stagnant and are chronically polluted. Korn et al. have stated that toluene is more toxic than many other hydrocarbons such as benzene, though the latter are more water-soluble. Report of the effects of …

Acute lethal toxicity of some pesticides toBrachionus calyciflorus andBrachionus plicatilis

1991

Due to their widespread distribution and toxic nattwe pesticides may have a serious impact on the aquatic environment and exert adverse effects on the associated organisms. Acute bioassay tests have been used to determine the actual impact of various pesticides on aquatic life. Static acute toxicity tests provide rapid and reproductible concentration-response curves for estimating toxic effects of chemicals on aquatic organisms. These tests provide a data base for determining relative toxicity to a variety of species.

Comparative toxicant sensitivity of sexual and asexual reproduction in the rotiferBrachionus calyciflorus

1995

Cyclically parthenogenetic zooplankters like rotifers are important tools for assessing toxicity in aquatic environments. Sexual reproduction is an essential component of rotifer life cycles, but current toxicity tests utilize only asexual reproduction. The authors compared the effects of four toxicants on asexual and sexual reproduction of the rotifer Brachionus calyciflorus. Toxicants had a differential effect on sexual and asexual reproduction, with sexual reproduction consistently the most sensitive. Concentrations of 0.2 {mu}g/ml PCP (sodium pentachlorophenate) had no effect on the asexual reproductive rate, but significantly reduced sexual reproduction. Likewise, chlorpyrifos concentr…

Chronic toxicity of fenitrothion to an algae (Nannochloris oculata), a rotifer (Brachionus calyciflorus), and the cladoceran (Daphnia magna).

1996

Chronic toxicity studies were conducted with an algae (Nannochloris oculata), a rotifer (Brachionus calyciflorus), and a cladoceran (Daphnia magna) to determine their relative sensitivities to the organophosphorus insecticide fenitrothion. The cladoceran D. magna was the most sensitive of the three species. The no observed effect concentrations (NOECs) for the study with the algae (1.0 mg/liter) and for the rotifer (1.0 mg/liter) were higher than the NOEC (0.009 microgram/liter) and the LC50 of 24 hr (0.067 microgram/liter) for D. magna. Most of the algal populations were not initially affected by exposure to fenitrothion. Pesticide concentrations higher than 1.0 mg/liter significantly redu…

Does haplodiploidy purge inbreeding depression in rotifer populations?

2009

Background Inbreeding depression is an important evolutionary factor, particularly when new habitats are colonized by few individuals. Then, inbreeding depression by drift could favour the establishment of later immigrants because their hybrid offspring would enjoy higher fitness. Rotifers are the only major zooplanktonic group where information on inbreeding depression is still critically scarce, despite the fact that in cyclical parthenogenetic rotifers males are haploid and could purge deleterious recessive alleles, thereby decreasing inbreeding depression. Methodology/Principal Findings We studied the effects of inbreeding in two populations of the cyclical parthenogenetic rotifer Brach…

Effect of sublethal diazinon concentrations on the demographic parameters of Brachionus calyciflorus Pallas (Rotifera)

1992

A mathematical model for the phase of sexual reproduction in monogonont rotifers

2000

Recently, the optimal sex allocation in monogonont rotifers is studied in [1], and, as a closely related question, the relative frequencies of the relevant types of mictic females. The authors focus on the evolution of the age at which young mictic females lose their fertilization susceptibility and they address the threshold age of fertilization that maximizes resting egg production. Assuming that a stationary population is achieved, with stable age distribution, they obtain their results, without knowing the stationary population. Our aim is to study this problem in the framework of the theory of nonlinear age-dependent population dynamics developed by G. F. Webb in [13], which is more ap…