Protein patterns in rotifers: the timing of aging

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.     

A perspective on aging in rotifers

Most research on aging in rotifers has been performed with populations, not with individuals. As a consequence, the dependent variable in these studies is usually either mean lifespan or rate of survivorship. After a brief consideration of the literature published since the last major review (King, 1969), the results of a series of experiments are presented. Males and females of three genetically distinct clones of Brachionus plicatilis were used for a factorial life table analysis at three different temperatures. The results of these experiments indicate several potential problems in using populations to study the aging process of individuals. These problems derive from the fact that lifespan is only one component of fitness, and its relative duration may not reflect the evolutionary success of the clone. That is, lifespan is free to vary in response to both stochastic and deterministic events without significantly reducing fitness. Under these conditions, neither mean lifespan nor pattern of survivorship will provide meaningful data on the determinants of individual senescence.We gratefully acknowledge the aid and advice of William R. Rice in conduct of the regression analysis. This work was supported by grants from the National Science Foundation and National Institutes of Health to CEK.     

Contribution to the study of african rotifers: rotifers from Mali

In samples collected from different parts of the Republic of Mali (W-Africa), ninety-two taxa of rotifers were identified. Some were present in different forms; 56% were cosmopolitan, 19% thermophilous with a wide distribution, 20% tropicopolitan and 5% cold-stenothermous. These latter species seem to be relicts of palaeoclimatic conditions in Africa.     

Relation to habitat in rotifers

Rotifera should be especially suited for an analysis of habitat relations because this group contains such a high number of species, inhabiting diverse environments. Furthermore, rotifers are to a large extent cosmopolitan, implying that ecological barriers, rather than geographical, are decisive of their distribution. In this review a short characterization of the rotifer fauna in different habitats is given, whereby macroenvironments and microenvironments are reported separately. The macroenvironments are classified as follows: harmonious lakes and ponds, arctic and antarctic waters, hot springs, hypertrophic-saprobic environments, mires, strongly acidic waters, saline waters, temporary water bodies, subterranean waters, running waters, oceans, terrestrial environments. The following microenvironments are distinguished: macrophytes (housing periphytic rotifers), open water (with planktic forms), minerogenous sediments (with psammon and hyporheos), organogenous sediments, other organisms (i.e. parasites and epizoans).Many rotifers are more or less euryecious, while relatively few are strongly restricted in their choice of habitat. In extreme environments a low number of species is found, but often a high number of individuals within these species. These rotifers are usually primary consumers, and for natural reasons extreme environments are characterized by a low number of trophic levels.In environments with a high species number the separate species differ very much in their morphology, making it difficult to find common traits which may be interpreted as adaptations to the respective habitats. The most apparent adaptations ought to be found among the planktic rotifers, and these adaptations seem to constitute largely a protection against predators. Rotifers in extreme environments are usually not very apart in a morphological or taxonomical respect, with their most close relatives living in normal habitats and sometimes euryecious (an apparent exception from this rule is formed by the class Seisonidea). Adaptations to deviating chemical and physical environments may develop relatively rapidly (seen from a geological perspective), while the more fundamental changes (occurring during a longer period of time) seem to be a response to biotic factors (e.g., the development of different types of trophi for facilitating food collection).     

Contributions to the knowledge of African Rotifers I. Rotifers from Senegal

24 plankton samples, collected in different parts of the Republic of Senegal (W. Africa) were examined for their rotifer content. Seventy taxa were identified to species level, some of which were present in different forms. Thirty three taxa and forms are new to Senegal, three species are new to Africa. Attention is paid to a cruciform population of Asplanchnella sieboldi and to a Brachionus quadridentatus population of very small dimensions. Two new taxa are described: Brachionus cf. angularis and Brachionus bidentatus senegalensis Koste & De Ridder.     

Rotifers as indicators of lake types in Estonia

Data on the pelagic rotifer fauna in 10 Estonian lakes accumulated for 20 years, as well as published data are analysed. It is possible to distinguish three main indicator groups among rotifers: (1) for oligo- and mesotrophic lakes (Ploesoma hudsoni, Keratella serrulata, Synchaeta grandis, Asplanchna herricki, Ascomorpha ovalis, Gastropus stylifer, Conochilus hippocrepsis); (2) for meso-and eutrophic lakes (Trichocerca capucina, Filinia longiseta, F. limnetica, Keratella quadrata, K. cochlearis tecta, K.c. hispida, Polyarthra euryptera, Keratella hiemalis, Trichocerca porcellus, T. pusilla); (3) for eutrophic lakes (Brachionus spp., Anuraeopsis fissa, Pompholyx sulcata, P. complanata, Trichocerca cylindrica, Hexarthra mira).     

Some rotifers from Republic of Korea

The author gives account of rotifers found at ten locations in the Republic of Korea, and elaborates some detail of specimens encountered with remarks and drawings. Thirty-seven different rotifer species were found, mostly belonging to the Order Monogononta. Twenty-two are new to the species list compiled by Yamamoto (1953). Keratella hiemalis was found for the first time in Asia. To date, one-hundred and two species of rotifers have been found in Korea.     

Rotifers in ecotoxicology: a review

In the past five years the use of rotifers in ecotoxicologial studies has substantially increased. This greater interest has been due to the central role of rotifers in freshwater planktonic communities, the ease and speed of making quantitative measurements of mortality and reproduction, their sensitivity to common pollutants, the commercial availability of cysts, and the existence of reliable, standardized protocols. The main endpoints used in ecotoxicology studies are reviewed, including mortality, reproduction, behavior, cellular biomarkers, mesocosms, and species diversity in natural populations. For each endpoint, published studies are cited, along with the compounds investigated, duration of exposure, and the LC50s, EC50s or NOECs reported. Rotifers have been included as part of a standardized mesocosm and in several large-scale, outdoor mesocosm studies. A critique of rotifer use in ecotoxicology is offered and it is concluded that the scientific basis for including rotifers as part of a battery of ecotoxicological tests is well established.     

Benefits,costs and reactivity of inducible defences: an experimental test with rotifers

1. A key aspect of the ecology and evolution of adaptive prey responses to predator risk is the timing by which the former develop a defensive trait in response to inducing signals released by the latter. This property, called reactivity, has been shown to affect population stability and persistence. 2. Theoretically, the minimal predator density required by prey to exhibit induced defences is expected to increase with the effectiveness of the defence and decrease with its cost. Likewise, the time required for the prey population to exhibit an induced defence is expected to increase together with cost. 3. The freshwater rotifers Brachionus calyciflorus and B. havanaensis and their predator Asplanchna brightwelli were used to test the hypothesis that prey species exhibiting defences that offer a larger fitness benefit and lower fitness cost are more reactive to predator signals, in terms of requiring shorter exposure time and lower signal concentration to trigger a morphological defence reaction. 4. Our results showed that both prey species exhibited costly and effective defences after induction by predator infochemicals. Faster reactions were observed at higher levels of predator cues. Nevertheless, the observed relationship between reactivity and benefit/cost of defences did not agree with our expectations. 5. To our knowledge, this is the first study in which the timing of induction of morphological defences is experimentally assessed over a gradient of risk signals. We propose new research directions to disentangle the mechanisms and project the consequences of prey decisions at the morphological level.     

Physiological responses to variable environments: storage and respiration in starving rotifers

1. Zooplankton exist in environments where food availability varies greatly over time, and success depends in part on the ability to store resources when food is abundant and to conserve them when food is scarce. This paper reports on interspecific differences in the size of stored reserves, and in respiration rate during food deprivation, of four species of planktonic rotifers.
2. The size of reserves varied from 42 to 71% of initial (well-fed) body mass. Interspecific differences in reserve size explained some of the previously observed differences in starvation time.
3. The initial response of respiration rate to food deprivation was quite variable between species. Brachionus calyciflorus was the only species to conserve energy by decreasing respiration rate in response to food deprivation. In contrast, the respiration rate of starved Asplanchna priodonta increased, while that of A. silvestrii and Synchaeta pectinata did not change, during food deprivation.
4. Theory predicts that temporal variation in resource level may facilitate the coexistence of competing species. This theory depends upon trade-offs between traits that confer competitive success in different environments. Although rotifers show a trade-off between competitive ability and maximum population growth rate, we found no evidence for trade-offs between either of those two traits and the size of reserves.     

Cellular aging beyond cellular senescence: Markers of senescence prior to cell cycle arrest in vitro and in vivo

The field of research on cellular senescence experienced a rapid expansion from being primarily focused on in vitro aspects of aging to the vast territories of animal and clinical research. Cellular senescence is defined by a set of markers, many of which are present and accumulate in a gradual manner prior to senescence induction or are found outside of the context of cellular senescence. These markers are now used to measure the impact of cellular senescence on aging and disease as well as outcomes of anti‐senescence interventions, many of which are at the stage of clinical trials. It is thus of primary importance to discuss their specificity as well as their role in the establishment of senescence. Here, the presence and role of senescence markers are described in cells prior to cell cycle arrest, especially in the context of replicative aging and in vivo conditions. Specifically, this review article seeks to describe the process of “cellular aging”: the progression of internal changes occurring in primary cells leading to the induction of cellular senescence and culminating in cell death. Phenotypic changes associated with aging prior to senescence induction will be characterized, as well as their effect on the induction of cell senescence and the final fate of cells reviewed. Using published datasets on assessments of senescence markers in vivo, it will be described how disparities between quantifications can be explained by the concept of cellular aging. Finally, throughout the article the applicational value of broadening cellular senescence paradigm will be discussed.     

Genetically engineered mice and their use in aging research

Genetically engineered animal models have been and will continue to be invaluable for exploring the basic mechanisms involved in the aging process as well as in extending our understanding of diseases found to be more prevalent in the older human population. Continued development of such in vivo systems will allow scientists to further dissect the role genetic and environmental factors play in aging and in age-related disease states and to enhance our understanding of these processes. In this article we discuss techniques involved in the development of such models and review some examples of laboratory mouse strains that have been used to study either normal aging or select diseases associated with aging.     

Rotifers as indicators of water quality

Six hundred and twenty species and lower taxonomical units of Rotatoria found in Czechoslovakia and surrounding countries are listed alphabetically and classified according to water quality. The numerical characteristics include the saprobic valence in 10 balls, the indicative weight of species, I_i, and the individual saprobic index, S_i. Rotifers are considered to be good indicators and some of them are figured on Plates 1–3. The situation is illustrated by four graphs and the relation to BOD₅ values is stressed. All rotifers are aerobic organisms and occur only within limnosaprobity. They can also serve as indicators of trophic conditions. To characterize the situation in standing and slowly flowing waters a Brachionus: Trichocerca quotient is proposed. Rotifers can also be used as test organisms in toxicity experiments.     

衰老机制及其学说

不同物种,同一个体的不同组织和细胞,它们的衰老速度并不相同。究其原因,遗传与环境都能影响衰老的进程。个体的平均寿命和物种的最高寿限可以从不同侧面反映衰老的进程。目前认为平均寿命主要与环境相关,而物种最高寿限与遗传相关。从两者的关系看,不良环境影响是通过对遗传物质或其产物的作用而影响衰老的进程。从遗传因素看,衰老并非由单一基因或单一作用所决定,而是一连串基因激活和阻抑及其通过各自产物相互作用的结果。DNA（特别是线粒体DNA）并不像原先设想的那样稳定,目前业已证明,包括基因在内的遗传控制体系可受内、外环境,特别是氧自由基等损伤因素的影响,从而加速衰老的进程。     

Proteomics in aging research: A roadmap to clinical,translational research

The identification of plasma proteins that systematically change with age and, independent of chronological age, predict accelerated decline of health is an expanding area of research. Circulating proteins are ideal translational “omics” since they are final effectors of physiological pathways and because physicians are accustomed to use information of plasma proteins as biomarkers for diagnosis, prognosis, and tracking the effectiveness of treatments. Recent technological advancements, including mass spectrometry (MS)‐based proteomics, multiplexed proteomic assay using modified aptamers (SOMAscan), and Proximity Extension Assay (PEA, O‐Link), have allowed for the assessment of thousands of proteins in plasma or other biological matrices, which are potentially translatable into new clinical biomarkers and provide new clues about the mechanisms by which aging is associated with health deterioration and functional decline. We carried out a detailed literature search for proteomic studies performed in different matrices (plasma, serum, urine, saliva, tissues) and species using multiple platforms. Herein, we identified 232 proteins that were age‐associated across studies. Enrichment analysis of the 232 age‐associated proteins revealed metabolic pathways previously connected with biological aging both in animal models and in humans, most remarkably insulin‐like growth factor (IGF) signaling, mitogen‐activated protein kinases (MAPK), hypoxia‐inducible factor 1 (HIF1), cytokine signaling, Forkhead Box O (FOXO) metabolic pathways, folate metabolism, advance glycation end products (AGE), and receptor AGE (RAGE) metabolic pathway. Information on these age‐relevant proteins, likely expanded and validated in longitudinal studies and examined in mechanistic studies, will be essential for patient stratification and the development of new treatments aimed at improving health expectancy.     

Competition in variable environments: experiments with planktonic rotifers

1. In a constant environment, competition often tends to reduce species diversity. However, several theories predict that temporal variation in the environment can slow competitive exclusion and allow competing species to coexist. This study reports on laboratory competition experiments in which two pairs of planktonic rotifer species competed for a phytoplankton resource under different conditions of temporal variability in resource supply.
2. For both species pairs, Keratella cochlearis dominated under all conditions of temporal variability, and the other species ( Brachionus calyciflorus or Synchaeta sp.) almost always went extinct. Increasing temporal variation in resource supply slowed competitive exclusion but did not change competitive outcome or allow coexistence.
3. Rotifers show a gleaner–opportunist trade-off, because gleaner species have low threshold resource levels ( R *) and low maximum population growth rates, while opportunist species have the opposite characteristics. In the competition experiments, the gleaner always won and the opportunists always lost. Thus, a gleaner–opportunist trade-off was not sufficient to facilitate coexistence under conditions of resource variability. Instead, the winning species had both the lowest R * and the greatest ability to store resources and ration their use during times of extreme resource scarcity.     

A new method to estimate individual dry weights of rotifers

Body and egg volumes of 12 rotifer species of Lake Constance were calculated from more than 18 000 individually measured animals using geometric approximations. Body (V _A) and egg (V _E) volumes of various rotifer species have an allometric relationship described by: V _E = 1272 · V _A ^0.3379, while the relation V _E/V _A for each species was constant ranging from 0.016 to 0.87. Dry weight of adult rotifers was assumed to be the sum of the egg dry weight plus a corrected weight increment from egg to adult. It was estimated with the formula W _A = W _E · (1 + a · F _A/F _E) where (a) was varied between 0 and 0.1. Egg dry weight content was assumed to be 35 % of fresh weight. The estimates of dry weight to wet weight ratios ranged from 0.57 % (Asplanchna priodonta) to 29.4 % (Kellicottia longispina). Dry weight estimates obtained with this method are comparable to those obtained with direct measurements of dry weight or carbon content.This investigation was supported by the Deutsche Forschungsgemeinschaft within the Special Collaboration Program (SFB) Cycling of Matter in Lake Constance.     

Distribution of rotifers in North Island,New Zealand,and their potential use as bioindicators of lake trophic state

The distribution and ecology of planktonic rotifers was investigated in 33 lakes in the North Island, New Zealand, between 1997 and 1999. A total of 79 species of monogonont rotifer were identified, with an average of 21 species per lake, a diversity which is high in comparison with many previous New Zealand studies. Most species recorded were cosmopolitan taxa, and were widespread in their distribution over the North Island. Multivariate analyses (Multi-Dimensional Scaling and Canonical Correspondence Analysis) did not distinguish distinct lake groupings based on rotifer communities, but rather gradients in assemblages, which were most highly associated with lake trophic state. Based on these responses, the development of potential rotifer bioindicator schemes for lake trophic state is described and discussed.     

Aneuploidy in human sperm: the use of multicolor FISH to test various theories of nondisjunction.

While it is known that all chromosomes are susceptible to meiotic nondisjunction, it is not clear whether all chromosomes display the same frequency of nondisjunction. By use of multicolor FISH and chromosome-specific probes, the frequency of disomy in human sperm was determined for chromosomes 1, 2, 4, 9, 12, 15, 16, 18, 20, and 21, and the sex chromosomes. A minimum of 10,000 sperm nuclei were scored from each of five healthy, chromosomally normal donors for every chromosome studied, giving a total of 418,931 sperm nuclei. The mean frequencies of disomy obtained were 0.09% for chromosome 1; 0.08% for chromosome 2; 0.11% for chromosome 4; 0.14% for chromosome 9; 0.16% for chromosome 12; 0.11% for chromosomes 15, 16, and 18; 0.12% for chromosome 20; 0.29% for chromosome 21; and 0.43% for the sex chromosomes. Data for chromosomes 1, 12, 15, and 18, and the sex chromosomes have been published elsewhere. When the mean frequencies of disomy were compared, the sex chromosomes and chromosome 21 had significantly higher frequencies of disomy than that of any other autosome studied. These results corroborate the pooled data obtained from human sperm karyotypes and suggest that the sex chromosome bivalent and the chromosome 21 bivalent are more susceptible to nondisjunction during spermatogenesis. From these findings, theories proposed to explain the variable incidence of nondisjunction can be supported or discarded as improbable.     

Analysis of protein,carbohydrate and lipid in rotifers

Protein, carbohydrate and lipid amounts were determined for several rotifer species collected directly from the field. Brachionus calyciflorus was the most abundant species; therefore making possible more data for it. An increase in protein content of this species occurred when its concentration in food (µg protein/ml) also increased. Keratella tropica showed a similar pattern, but Asplanchna brightwelli did not.Carbohydrate proved to be the main form of storage in rotifers. In Brachionus calyciflorus females bearing no egg, 8% of the total biomass was carbohydrate; in females bearing one egg, 15% carbohydrate was found. Lipid does not appear to be used for storage since no increase in the amount of lipid was detected in females bearing eggs or embryos. This suggests that lipid has a structural function. Finally, a relationship between rotifer body volume and protein content at a given food concentration was obtained. The cladoceran Daphnia magna follows the same pattern.