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1.
A perspective on aging in rotifers   总被引:1,自引:8,他引:1  
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.  相似文献   

2.
M. De Ridder 《Hydrobiologia》1992,237(2):93-101
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.  相似文献   

3.
Relation to habitat in rotifers   总被引:2,自引:2,他引:2  
Pejler  Birger 《Hydrobiologia》1995,313(1):267-278
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).  相似文献   

4.
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.  相似文献   

5.
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.  相似文献   

6.
Rotifers in ecotoxicology: a review   总被引:30,自引:3,他引:30  
Snell  Terry W.  Janssen  Colin R. 《Hydrobiologia》1995,313(1):231-247
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.  相似文献   

7.
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.  相似文献   

8.
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.  相似文献   

9.
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.  相似文献   

10.
Rotifers as indicators of water quality   总被引:37,自引:10,他引:37  
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, Ii, and the individual saprobic index, Si. 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.  相似文献   

11.
Duggan  I.C.  Green  J.D.  Shiel  R.J. 《Hydrobiologia》2001,(1):155-164
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.  相似文献   

12.
Hirschfelder  A.  Koste  W.  Zucchi  H. 《Hydrobiologia》1993,255(1):343-344
The rotifer species composition from two different moss species growing on roofs of different ages was investigated.  相似文献   

13.
Pejler  Birger  Bērziņš  Bruno 《Hydrobiologia》1989,(1):137-144
Information on the distribution of 28 rotifers of the family Brachionidae from diverse waters in south and central Sweden was analyzed to reveal their relationships to substrate and habitat. Some brachionids are preferably planktic, others periphytic and/or benthic. Some non-planktic habitats are utilized more than others, but there is no evidence of a chemical attraction from any substrate. Instead, some substrates seem to be avoided, possibly depending on a poorer flora of periphytic algae. Besides substrate type, the following factors are found to be important for creating separate ecological niches in the brachionid family: temperature, oxygen content, trophic degree, chemical environment, food choice and sensitivity to predation. It is possible to delineate separate ecological niches for all brachionid rotifers, implying that Hutchinson's ideas about the plankton paradox are contradicted. Some species are specialists, other are generalists, the latter being characterized by a great morphological variation. The species are adapted in different ways to their preferential habitats, as regards foot, egg-carrying, protrusions and other lorical structures etc. Longer spines, for instance, are generally found in more transparent water, being a supposed protection against visual predators.  相似文献   

14.
Pejler  Birger  Bērziņš  Bruno 《Hydrobiologia》1993,(1):333-338
Information on the distributions of 77 bdelloid rotifers from diverse waters in south and central Sweden was analyzed to reveal their relationships to substrate and habitat. Only two species were reported from plankton, both in low frequency. An artificial substrate, white cotton, was utilized only by few bdelloids, mainly by species with eyes. Only one species occurred at higher frequency on the saprobic substrate Sphaerotilus. Most bdelloids prefer environments rich in oxygen, but some species may be found in soft-bottom sediments. Several species dwell preferentially in diverse habitats of bogs. Some bdelloids have an exceptionally broad ecological range, but even for these is it possible to distinguish a pattern of preference and avoidance.  相似文献   

15.
Abundance and diversity of planktonic rotifers in the Po River   总被引:3,自引:8,他引:3  
Ferrari  I.  Farabegoli  A.  Mazzoni  R. 《Hydrobiologia》1989,186(1):201-208
Zooplankton samples from the middle reach of the Po River were collected daily from 27 July to 24 August 1988 from a station located near Viadana. Changes in the biocoenosis structure were analyzed in relation to variations in flow rate. Rotifers accounted for more than 99% of the total zooplankton (protozoans excluded) in every sample. The dominant species were Brachionus calyciflorus, Brachionus bennini, Brachionus budapestinensis and Epiphanes macrourus. Under scanty flow conditions, the taxocoenosis showed marked stability. An increase in flow rate acts as a disturbance factor leading to a significant decrease in both total density and dominance.  相似文献   

16.
Pierre Clement 《Hydrobiologia》1987,147(1):339-359
In this review, original observations on rotifer cilia and muscles are used to explain the mechanism of their movements. The following topics are discussed: (1) cilia and infraciliature of the cingulum, (2) muscle insertions into the infraciliature, (3) innervation of the muscles and non-innervation of the ciliated cells, (4) recent data on the location of gap junctions which link some muscles, (5) cilia and infraciliature of the cirri of the pseudotrochus of Brachionus calyciflorus, and the insertion of muscles onto their infraciliature, (6) the relation between muscles and integument in the foot of Philodina roseola, (7) the relation between muscles and integument in the joint present at the base of the tail of Trichocerca rattus, and (8) hypotheses on the first articulated (muscle-integument) movements which exist alongside ciliary motion in certain rotifers.Neuro-ethological summaries, based on data of the effectors and on observations on behavior and the sensitivity of rotifer sensory receptors (reviewed in Clément et al., 1983), are attempted. A more complete analysis is provided in the following instances: (1) swimming and the mechanism of turning, (2) retraction of the rotatory apparatus, (3) feeding behavior in Trichocerca rattus involving the succession swimming, crawling and nutrient intake.Other behavioral sequences, for which the ethological and ultrastructural data are incomplete, are presented and briefly discussed.Lastly, the argument is put forward that rotifers constitute an exceptional model for comparative, neuroethological studies which may enable us to better understand the mechanisms of evolution. Carrying out detailed observations, aimed at understanding how certain movements occur, should enable us to gain insights into the question of why they exist.  相似文献   

17.
M. De Ridder 《Hydrobiologia》1987,150(2):123-131
The number of Rotifer taxa known from Mauritania, is raised from 8 to 90. 61% of these are cosmopolitan, 1 is temperate — boreal, 18% are thermophilic and 20% are tropicopolitan. Most of them are widely distributed in Africa, but some species have limited distributions. The presence of Keratella testudo and Wolga spinifera is remarkable and is probably related to the unusual climatic conditions in the SW Sahara. One phenotype or forma is new to science.  相似文献   

18.
A mesocosm experiment was conducted “in situ” in a Chara dominated shallow lake near Valencia (Spain) to study top–down and bottom–up effects on rotifers by means of nutrient and fish additions. Both processes were important in determining rotifer abundance, biomass and diversity. A total of 36 mesocoms were established with triplicate treatment combinations of three fish levels (from no fish to 45 individuals of Gambusia holbrooki males) and four nutrient enrichment levels (from no additions to 10 mg l−1 nitrate-N and 1 mg l−1 phosphate-P). The main effect was a notable increase of planktonic and plant associated rotifers densities with fish. Rotifers benefited from mosquitofish predation on microcrustaceans and chironomids. The results showed a marked negative relationship between rotifer and cyclopoid abundances, indicating the importance of the predatory pressure of cyclopoids on rotifers. Effects on rotifer diversity were also evident, in general rotifer diversity decreased with nutrients and increased with fish. The effects of nutrients analysed at species level showed two contrasting density responses: an increase or a decrease with nutrients, which levelled off at high nutrient concentrations. High-level nutrient additions (from 5 mg l−1 nitrate-N and 0.5 mg l−1 phosphate-P) induced a switch to a turbid state with macrophyte disappearance. Most planktonic rotifer species, as well as plant associated ones, diminished when the turbid state was well established, especially in the mesocosms without fish. In the turbid mesocosms, relative abundance of plant-associated rotifers (as a whole) was higher than that of planktonic rotifers. The changes in rotifer species composition after the switch from a clear to a turbid water state are also described. Species of the genus Anuraeopsis, Trichocerca and Hexarthra, dominant in the clear water state, practically disappeared in the turbid water state, in which Proalides tentaculatus and Lecane nana were the main species. Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez Advances in Rotifer Research  相似文献   

19.
The hypolimnetic rotifer populations of the Pluss-see (Keratella hiemalis, Filinia terminalis, Filinia hofmanni) show similar patterns of changing population parameters indicating that they respond to particular environmental signals in the same way.  相似文献   

20.
Vertical distribution of planktonic rotifers is described in relation to temperature and oxygen in Lake La Cruz, a single-doline, closed karstic lake (121 m diameter and 25 m maximum depth) which shows iron meromixis. Samples were taken by peristaltic pumping at 10 cm depth intervals in the oxycline zone from June 1987 to September 1988. A model of rotifer vertical structure in stratified lakes is proposed. Rotifers concentrate their populations at the depths with intense gradients. As stratification develops some rotifer populations show a downward migration following the thermocline and some others show an upward migration following the oxycline. The production-respiration balance in the lake, and so the position of the oxycline with respect to the thermocline and the layer of maximum production, depends on meteorological conditions. A shift in the dominance of congeneric or related species can occur in consecutive years. In Lake La Cruz, mixing conditions and subterranean inflow in spring were much more intense in 1988 than 1987, and the distance between production and decomposition depths was smaller in 1988. Anuraeopsis miraclei, an oxycline-bound species with high abundance in 1987, was displaced by A. fissa in 1988. A. fissa, which was a metalimnetic species during early summer, reached peak densities (3 × 104 ind l–1) at the oxycline, equaling the abundance of A. miraclei the preceeding year.  相似文献   

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