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1.
Effects of food quality and starvation on the optimal foraging behavior of Daphnia magna (Cladocera)
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In the present work, we evaluated the feeding selectivity of starved Daphnia magna on two freshwater green algae Chlamydomonas sajao and Chlorellapyrenoidosa. Compared to C. pyrenoidosa, food quality of C. sajao are better in food palatability (cell size and digestibility), but poor in nutritional content (total carbon content). D. magna was starved for 0 and 8 d, and then was allowed to graze on a mixture of C. sajao and C. pyrenoidosa with following proportion: 5 × 104: 35 × 104 cells ml?1, 20 × 104: 20 × 104 cells ml?1 and 35 × 104: 5 × 104 cells ml?1. The results indicated that the ingestion rate and filtration rate of starved D. magna, comparing with satiated groups, on C. pyrenoidosa increased significantly, while, inverse trends was observed in C. sajao. Base on selectivity coefficient of D. magna, we observed that when D. magna was in satiation C. sajao will be preferred, while, C. pyrenoidosa will be selected when D. magna was in starvation, and moreover, these foraging behaviors were not influenced by the relative food abundance of each green alga. Therefore, a tradeoff between food palatability (physical makeup) and food nutritional content (chemical composition) can be hypothesized in the foraging behavior of D. magna, which is modified by the starvation of feeder. High valuable food is always selected by D. magna as predicted by optimal foraging theory. However, when D. magna is in satiation food diets with adequate size and easy digestibility will be preferred, while, those foods with relatively higher lipid or total carbon content will be selected when D. magna is in starvation. 相似文献
2.
The effect of starvation on sexual reproduction in cyclic parthenogenetic rotifers has been studied using life history experiment. Short-time starvation of rotifers that experienced starvation immediately after hatching from resting eggs can cause high induction of sexual reproduction up to the 10th generation. However, it is not clear whether the induction of sexual reproduction can occur beyond the 10th generation. To investigate this phenomenon, we conducted a sex induction study using the monogonont rotifer Brachionus manjavacas. Newborn stem females were starved for 12 h, while controls were supplied with 7.0 × 106 cells ml?1 of Nannochloropsis oculata. In a life history experiment, the rotifers were individually cultured in 96-well microplates containing 0.2 ml of seawater (22 ppt) in each well at 25 °C with daily feeding thereafter. Mixis induction in offspring from starved stem females was significantly higher than in those from non-starved stem females up to the 40th generation. The effect of accumulative generations increased mixis induction up to the 20th generation. Effect on future generations of the rise in mixis ratio by the starvation to stem females may facilitate colonization by favoring population growth via female parthenogenesis and by decreasing food requirements for survival and reproduction. 相似文献
3.
Fred J. Genthner Janeshwar Upadhyay Robert P. Campbell Barbara R. Sharak Genthner 《Microbial ecology》1990,20(1):283-288
Culturable counts of antibiotic resistant, genetically engineeredPseudomonas fluorescens were determined on antibiotic-containing plate count agar during starvation in water. Prior to starvation, colony counts
obtained on all media separated into two groups. The mean of the colony counts on plate count agar with or without tetracycline
(4.9 × 106 ml−1) was significantly higher than the mean colony counts on plate count agar containing either nalidixic acid or nalidixic acid
plus tetraclycline (2.5×106 ml−1). After 20 days of starvation the highest mean colony counts continued to be obtained on plate count agar (7.2 × 106 ml−1) with slightly, but significantly, lower counts obtained on plate count agar containing either nalidixic acid (5.6 × 106 ml−1) or tetraclycline (1.5×106 ml−1). A combination of nalidixic acid and tetracycline in plate count agar, however, dramatically reduced colony counts (8.3
× 102 ml−1) after this starvation period. The addition of catalase to plate count agar containing nalidixic acid and tetracycline negated
the effect caused by this combination of antibiotics. When colony counts obtained over the entire 20 day incubation were considered,
the addition of MgSO4 to plate count agar containing nalidixic acid and tetracycline resulted in a significant increase in colony counts. Other
combinations of antibiotics, nalidixic acid+carbenicillin, nalidixic acid+kanamycin, streptomycin+tetracycline, streptomycin+carbenicillin,
rifampicin+tetracycline, rifampicin+carbenicillin, and rifampicin+kanamycin, did not inhibit colony formation of starved cells.
Antibiotic resistant strains ofP. putida andEscherichia coli also displayed sensitivity to the combination of nalidixic acid and tetracycline in plate count agar after starvation. 相似文献
4.
Effects of starvation on the suryival period and the respiratory rate in adults of a wolf spider, Pardosa astrigera (L. Koch ), were investigated. The spiders used were divided into four groups: well-fed, starved and two limited food groups; in the latter two, each spider was supplied with one leafhopper every second or third day. Adult males and females of P. astrigera could survive for a long time; 28.8±2.7 days and 54.4±18.9 days, respectively, without any food. The longevities shown here were 73.8% for males and 78.6% for females of those of well-fed spiders, indicating that P. astrigera adults have a strong tolerance to starvation. The respiratory rate of well-fed adults showed no tendency to increase or decrease with their aging; the mean respiratory rates were 4.86×10−4 mg CO2/mg f.w. (fresh body weight)/hr for males and 3.80×10−4 mg CO2/mg f.w./hr for females. The respiratory rates of starved spiders increased during the first two days of starvation but decreased markedly from the third to the twelfth day, and thereafter retained an almost constant level for each sex. The mean respiratory rates after the twelfth day of starvation were 2.49×10−4 mg CO2/mg f.w./hr for males and 2.76×10−4 mg CO2/mg f.w./hr for females; these values were respectively 48.4% and 63.0% of those prior to starvation. The fresh body weight of starved spiders decreased linearly with time but the rate was small. The respiratory rates of the limited food groups tended to decline with time and thereby their weight losses were minimized. The decrease in the respiratory rate under starvation was considered not to be due to spider exhaustion or senescence but due to an intrinsic change in behaviour and/or metabolism, because when the spiders were supplied with ample food for five days after starvation, the respiratory rate and the body weight rapidly recovered to near the levels prior to starvation. It is suggested that starved spiders use a higher ratio of fat as catabolic substrate than normally fed or satiated ones. Feeding strategies of poikilo-therm predators are discussed. 相似文献
5.
S. Kavadias J. Castritsi-Catharios A. Dessypris H. Miliou 《Zeitschrift fur angewandte Ichthyologie》2004,20(1):58-63
For a period of 1 year, some blood parameters were evaluated on a monthly basis in a population of adult European sea bass (Dicentrarchus labrax L.) intensively reared in floating marine cages (Ionian Sea, Mediterranean). From April (13 months old) to July (16 months old) males (35–50%) and sexually indeterminate individuals were collected. From August to March (24 months old) only males were sampled. During this period the percentage of spermiated males was highest (100%) from November (20 months old) to January (22 months old). Plasma testosterone in males was inversely related to sunlight (h month?1) and was elevated between October and January, when males first achieved sexual maturity. Testosterone showed the highest value (0.49 ± 0.02 ng ml?1) in January and the lowest (0.09 ± 0.02 ng ml?1) in March. Haematocrit, red blood cell counts and haemoglobin concentration were elevated from November to March, being inversely related to sunlight. The two latter parameters were also inversely related to daily food intake. Haematocrit, red blood cell counts and haemoglobin concentration were highest in December [53 ± 1%, (5.36 ± 0.06) × 106 mm?3, 10.08 ± 0.14 g 100 ml?1, respectively] and lowest in June [35 ± 1%, (3.33 ± 0.05) × 106 mm?3, 6.47 ± 0.13 g 100 ml?1, respectively]. White blood cell counts were not correlated with sea water temperature, sunlight or daily food intake. They were highest in February [(8.45 ± 0.20) × 104 mm?3] and lowest in April [(6.07 ± 0.14) × 104 mm?3]. Total plasma protein concentration (4.88 ± 0.11–5.93 ± 0.10 g 100 ml?1) and mean cell volume (93.3 ± 0.9–105.5 ± 1.8 μm3) showed small fluctuations throughout the year. Sexual maturity appears to be a major factor that significantly affects haemopoiesis of D. labrax. This study contributes to the evaluation of normal levels of some blood parameters in European sea bass, which are helpful for the assessment of physiological status and health of this species. 相似文献
6.
Joseph F. Ustach 《Journal of experimental marine biology and ecology》1982,64(3):203-214
The harpacticoid copepod, Heteropsyllus pseudonunni Coull and Palmer, when fed Juncus roemerianus Scheele (needlerush) detritus produced significantly more eggs than when fed the alga Dunaliella sp. Five food rations and a starved control were used: A, algal concentration ≈ 104 cells · ml?1; LA, algal concentration 103 cells · ml?1; D, detritus concentration 0.25 g · ml?1; LD, detritus concentration 0.025 g · ml?1; LDLA, a mixture of the LD and LA rations. Geometric mean total egg production values were: LDLA 132.5; LD 132.6; D 120.5; A 65.8; LA 5.0. The LA results were significantly less (P = 0.05; Student-Newman-Keuls' test) than all others, while the A results were significantly less than the LDLA, LD and D results. The LDLA, LD and D results were not statistically different. Similar trends were obtained when mean brood sizes and mean number of broods were compared. In a second feeding experiment, using Juncus detritus, bacteria on sand grains, and algae (Nitzschia sp.) on sand grains, Heteropsyllus pseudonunni produced significantly more eggs (P = 0.05; SNK test) when fed detritus (166.0) or bacteria (132.2) than algae (58.9). The detritus and bacteria results were not significantly different. 相似文献
7.
A behavioural bioassay was used to determine the response threshold to squid extract of sablefish, Anoplopoma fimbria, held at three different feeding regimens. Sablefish responded to the odour of bait by changing swimming activity and turning behaviour. The response threshold to bait odour was influenced by both the amount of food eaten and the duration of food deprivation. The total concentration of amino acids in the bait extract was assumed to determine the response threshold as chemical fractionation studies have shown that this class of compounds is essential for the stimulatory capacities of food extracts. When fed to satiation (9.4% wet body weight) and tested after one day of food deprivation, the mean response threshold to total dissolved free amino acids was 4.4 × 10?8m (range=7.6 × 10?8 to 3.6 × 10?8m ). When fed at 1.6-2.3% wet body weight, the threshold sensitivity had increased to a mean value of 1.8 × 10?10m (range=8.4 × 10?10 to 7.0 × 10?11m ) after one day of food deprivation; after four days of deprivation, the sensitivity had increased even further to a mean value of 1.4 × 10?11m (range=1.6 × 10?10 to 1.4 × 10?12m ). It was also apparent that the intensity of behavioural responses to the bait odour increased with both stimulus concentration and duration of food deprivation. These results suggest that sablefish intensify their search for prey under increased feeding motivation. The active space of a bait source was estimated from the threshold values obtained. Depending on state of food deprivation, rate of chemical release from the bait and the current velocity, maximum lengths of active space within which sablefish would exhibit food searching responses vary from 10 m to several km. Stock assessment based on catch data from baited gear will need techniques that take into account those factors influencing active space for food searching. 相似文献
8.
Yuki Kobayashi Yoshikuni Hodoki Kako Ohbayashi Noboru Okuda Shin-ichi Nakano 《Limnology》2013,14(1):43-49
We estimated the grazing impact of the heterotrophic flagellate Collodictyon triciliatum on the harmful, bloom-forming cyanobacterium Microcystis aeruginosa in an experimental pond during a Microcystis bloom from summer to winter in 2010. For these experiments, we calculated the grazing rates from the digestion rate of C. triciliatum and its food vacuole contents. During the study period, M. aeruginosa exhibited one bloom event with a maximum density of 1.1 × 105 cells ml?1. The cell density of C. triciliatum fluctuated from below the detection limit to 291 cells ml?1. The number of M. aeruginosa cells ingested by C. triciliatum food vacuoles ranged between 0.4 and 10.8 cells flagellate?1, and the digestion rate of C. triciliatum at 25 °C was 0.73 % cell contents min?1. The grazing rate of C. triciliatum on the M. aeruginosa prey was 0.2–6.9 cells flagellate?1 h?1, and its grazing impact was 0.0–25.3 % standing stock day?1. The functional response of C. triciliatum to the M. aeruginosa prey followed the Michaelis–Menten model of significance (r 2 = 0.873, p < 0.001) in our experimental systems, in which the prey concentration varied from 1.0 × 104 to 2.1 × 106 cells ml?1. The maximum grazing rate was 6.2 prey cells grazer?1 h?1, and the half-saturation constant was 1.2 × 105 cells ml?1. We present evidence that C. triciliatum grazing explained the remarkable decrease in M. aeruginosa cell density in the pond. The present study is the first demonstration of the high potential of protistan grazing on M. aeruginosa to reduce cyanobacterial blooms. 相似文献
9.
Aims: To develop probiotics for the control of vibriosis caused by Vibrio anguillarum and Vibrio ordalii in finfish. Methods and Results: Kocuria SM1, isolated from the digestive tract of rainbow trout, was administered orally to rainbow trout (Oncorhynchus mykiss) for 2 weeks at a dose equivalent to c. 108 cells per g of feed and then challenged intraperitoneally with V. anguillarum and V. ordalii. Use of SM1 led to a reduction in mortalities to 15–20% compared to 74–80% mortalities in the controls. SM1 stimulated both cellular and humoral immune responses in rainbow trout, by elevation of leucocytes (5·5 ± 0·8 × 106 ml?1 from 3·7 ± 0·8 × 106 ml?1), erythrocytes (1·2 ± 0·1 × 108 ml?1 from 0·8 ± 0·1 × 108 ml?1), protein (23 ± 4·4 mg ml?1 from 16 ± 1·3 mg ml?1), globulin (15·7 ± 0·2 mg ml?1 from 9·9 ± 0·1 mg ml?1) and albumin (7·3 ± 0·2 mg ml?1 from 6·1 ± 0·1 mg ml?1) levels, upregulation of respiratory burst (0·05 ± 0·01 from 0·02 ± 0·01), complement (56 ± 7·2 units ml?1 from 40 ± 8·0 units ml?1), lysozyme (920 ± 128·8 units ml?1 from 760 ± 115·3 units ml?1) and bacterial killing activities. Conclusions: Kocuria SM1 successfully controlled vibriosis in rainbow trout, and the mode of action reflected stimulation of the host innate immune system. Significance and Impact of the Study: Probiotics can contribute a significant role in fish disease control strategies, and their use may replace some of the inhibitory chemicals currently used in fish farms. 相似文献
10.
We speculated that Daphniopsis tibetana may be adapted to short-term lack of food through a mechanism of population growth compensation. D. tibetana were collected from Lake Namuka Co, Tibet, and acclimated to diluted seawater in 2007. All larvae used in experiments were synchronized newborn (<24-h old) and of an average body length of 790 (770–810) μm. We evaluated the effect of continuous starvation for 1, 3, 5, 7, 9, and 11 days and intermittent periods of starvation of 0.5, 1, 1.5, and 2 days on the compensatory population growth effect in D. tibetana. The duration of starvation significantly influenced population growth, body length, and heart rate. After 1 and 3 days of continuous starvation and 0.5 days intermittent starvation, the age of first reproduction was 16.3 days and the reproduction frequency was 0.8 (10 days?1), which were similar to the control group. In these two starved groups, lifetime fecundity values were 426.3 and 412.3, average life spans were 54.5 and 54.3 days, and intrinsic rates of increase (r m) were 0.136 and 0.133 days?1, respectively, which is significantly higher than the other starved groups and not different from the control group (P > 0.05). In the group with 7, 9, and 11 days of continuously starved groups, body lengths were significantly lower (P < 0.05) than those of controls. With increasing starvation time (1, 3, 5, and 7 days), heart rate progressively decreased (184, 178, 172, and 166 min?1). Body length, measured at the end of the experiment, declined with increasing duration of intermittent starvation. After 2 days of intermittent starvation, final heart rate sharply decreased to 150 min?1, which was highly significantly different from the other treatment groups. The results of this study conclude that D. tibetana is capable of complete compensatory population growth after short-term starvation. 相似文献
11.
The behaviour and oviposition of solitary endoparasitoid Microplitis pallidipes Szepligeti (Hymenoptera: Braconidae) were monitored to investigate the ability of the parasitoids to distinguish between nucleopolyhedrovirus (NPV)-infected and noninfected Spodoptera litura Fabricius (Lepidoptera: Noctuidae) larvae. The results indicated that the parasitoid searching time and the time until the first parasitoid attack on infected larvae were greater than those recorded on noninfected larvae; the number of infected larvae attacked by parasitoids, the percent of first attacks and parasitism rate in infected larvae were lower than those on noninfected larvae; and these differences were all significant 3 to 5 days postexposure of the larvae to a dose of 1.6 × 108 occlusion bodies (OB)· ml?1 and significant 4 and 5 days postexposure of the larvae to a dose of 1.6 × 107 OB·ml?1. The lowest dosage (1.6 × 106 OB·ml?1) had no significant effect on the above index values. In a field cage experiment, we found that the percentage of infected larvae parasitized by M. pallidipes gradually decreased as the time after NPV inoculation (1.6 × 108 OB·ml?1) increased, and that M. pallidipes significantly preferred to oviposit in healthy larvae from day 3 to day 5 after virus inoculation. Our research concluded that this parasitoid's ability to discriminate between healthy and infected hosts increased as virus concentration increased and as the time between exposure of hosts to virus and subsequent exposure to parasitoids increased. 相似文献
12.
M. Yúfera 《Hydrobiologia》2007,593(1):13-18
We examined feeding rates and swimming speed in amictic females of Brachionus plicatilis over algal cell concentrations ranging from 15 × 103 to 30 × 106 cell ml−1, to determine to what extent filtration rate is a consequence of a real modulation of swimming speed in response to food
availability. Swimming rates were measured using an automated motion analysis system via video recording. The results showed
that swimming speed changed as a function of food density. Swimming speed increased from the lowest tested concentration of
algae to reach a maximum at 6 × 106 cell ml−1. Above this density, swimming speed declined slightly and then remained constant at a mean speed of 0.45 mm s−1. Filtration and ingestion rates changed as cell concentration increased, following patterns consistent with those generally
described for suspension feeders. However, the observed swimming pattern did not explain the recorded changes in clearance
rate. These results suggest that filtration, and therefore ingestion, is mainly regulated by modifying particle retention
efficiency.
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
13.
Effects of food availability on the larval survival and development of Crepidula onyx were studied in four experiments by feeding the larvae with different concentrations of the chrysophyte Isochrysis galbana and by starving the larvae for different periods of time. Food concentration had a clear impact on the survival, growth and development time of C. onyx veligers. Larval development occurred only at 104 cells ml−1 and higher algal concentrations. No shell increment was detected in the veligers cultured for 12 days at 102 cells ml−1I. galbana or the blank control. At 103 cells ml−1, there was only a slight increase in shell length over 12 days. At 104 cells ml−1, about 40% of the larvae became competent in 18 days. At 105 and 106 cells ml−1, more than 90% of the larvae reached competence in 7 days. Initial starvation negatively affected the larval development, but the sensitivity differed among parameters measured on day 5: lower survivorship was detected only for larvae that had suffered 3 days or longer initial starvation, whereas one-day initial starvation caused shorter shells and lower percentage of competent larvae. Three days of continuous feeding was required for 50% of the larvae to reach competence. After feeding for 3 days, most larvae could become competent to metamorphose even under starvation. The time of starvation was also critical: larvae that suffered 1-day food deprivation in the first 2 days of larval release had shorter shells and lowered percent competent larvae than those that suffered the same length of food deprivation in later stages of development. Our study thus indicates that both food concentration and short-term starvation have detrimental effects on the larval development of this species, and that once the larva has consumed certain amount of food, starvation may induce metamorphosis. 相似文献
14.
The translational and rotational dynamics of tobacco mosaic virus in sodium phosphate buffer (pH =7.5) solutions has been investigated by polarized and depolarized light scattering Rayleigh linewidth studies. For concentrations ranging from 1.75 × 10?4 g ml?1 to 0.25 × 10?4 g ml?1 the translational diffusion coefficient (DT) has been found to be slightly concentration dependent and extrapolation to zero concentration gives D020°C = 0.34 ± 0.01 × 10?7 cm2S?1. A full analysis of the polarized spectra obtained at high and low scattering angles and the depolarized spectra at near zero scattering angles has enabled these techniques to be compared and the rotational diffusion constant DR to be determined. At a solution concentration of 1.75 × 10?4 g ml?1 a mean value is found to be DR20°C = 350 ± 30s?1. These values of DT and DR are in approximate agreement with calculations based on models of the tobacco mosaic virus molecule as a cylindrical rod. 相似文献
15.
Boglárka Somogyi Tamás Felföldi József Vanyovszki Ákos Ágyi Károly Márialigeti Lajos Vörös 《Aquatic Ecology》2009,43(3):735-744
The seasonal dynamics of picophytoplankton communities in shallow turbid alkaline pans in Hungary was studied between July 2006 and May 2007. Similarly to other aquatic environments in the temperate zone, dominance of picocyanobacteria was observed in summer and that of picoeukaryotes in winter. The mild winter in 2006–2007, with midday water temperatures of 5–10°C, resulted in large winter phytoplankton blooms (maximum chlorophyll a concentration 800 μg l?1) in the shallow pans. The phytoplankton was composed of single-celled picoeukaryotes and had a maximum of 108 × 106 cells ml?1 in Büdös-szék pan, 50 × 106 cells ml?1 in Kelemen-szék pan in April 2007, and 47 × 106 cells ml?1 in Zab-szék pan in March 2007. In order to explain the winter dominance of picoeukaryotes, we isolated picoeukaryotic and picocyanobacterial strains and determined the temperature and light dependence of their photosynthesis. Under temperatures <15°C, the photosynthetic activity of the picoeukaryotic strain was higher and their light utilization was better than those of the picocyanobacterial strain. The results indicate that low temperature and light intensity in winter provide a competitive advantage to picoeukaryotes, while higher temperatures and light intensity are more favorable for picocyanobacteria. 相似文献
16.
In vitro treatment of Babesia microti infected erythrocytes with mitomycin C before their injection into mice prolonged the prepatent period of infection, reduced the levels of the infection in the ‘breakthrough’ parasitaemia and induced protection against reinfection. Treatment of B. microti with mitomycin C at a concentration of 25 μg ml?1 resulted in a mean peak parasitaemia of 6.2% in the infected mice compared with 46.5% in control mice injected with untreated B. microti parasites. In addition, mice survived a normally fatal B. rodhaini infection if injected with 6.2 × 107 infected erythrocytes treated with 25 μg ml?1 mitomycin C and four of five mice survived infection with 6.2 × 105 similarly treated infected erythrocytes. However, the degree of protection against B. rodhaini was dependent on the concentration of mitomycin C used to treat the parasites and treatment of 5 × 107 infected erythrocytes with 50 μg ml?1 resulted in survival of only four of the five infected mice. In addition, when 100 μg ml?1 of mitomycin C was used to treat B. rodhaini parasites, the course of infection, although delayed, was indistinguishable from that seen in the control mice and all the mice died. The latter results and the lack of efficacy of comparable numbers of heat killed parasites suggested the necessity for sufficient, non-replicating, mitomycin C treated parasites to metabolize and produce and/or present protective antigens to the host. 相似文献
17.
Monchan Maketon Alongkorn Amnuaykanjanasin Achirayar Kaysorngup 《World journal of microbiology & biotechnology》2014,30(2):727-736
Twenty local isolates of entomopathogenic fungi were determined for control of the larvae and adults of Culex quinquefasciatus. In a laboratory experiment, a Penicillium sp. CM-010 caused 100 % mortality of third-instar larvae within 2 h using a conidial suspension of 1 × 106 conidia ml?1. Its LC50 was 3 × 105 conidia ml?1, and the lethal time (LT50) was 1.06 h. Cloning and sequencing of its internal transcribed spacer region indicated that this Penicillium species is Penicillium citrinum (100 % identity in 434 bp). Mortality of the adult was highest with Aspergillus flavus CM-011 followed with Metarhizium anisopliae CKM-048 from 1 × 109 conidia ml?1. P. citrinum CM-010 at 1 × 106 conidia ml?1 killed 100 % larvae within 2 h while Bacillus thuringiensis var. israelensis at 5 ITU ml?1 required 24 h. This P. citrinum CM-010 also greatly reduced survival of C. quinquefasciatus larvae in an unreplicated field test. Light and transmission electron micrographs showed that the fungal conidia were ingested by the larvae and deposited in the gut. The metabolite patulin was produced by P. citrinum CM-010 instead of citrinin. 相似文献
18.
Using the antibody-trapping technique, picogram quantities of angiotensin-I generated during 24 hr of incubation at 37°C were stable and fully protected against peptidases. The method employs purification of angiotensin-I antisera on DEAE-cellulose and purification of renin substrate by affinity chromatography using specific antirenin antibodies in order to remove endogenous renin. The assay was performed in a single tube without a transfer step in a total volume of 30 μl at pH 6,5 with incubation for 24 hr at 37°C. With a normal rat plasma renin concentration of 5 × 10?4 GU ml?1, the detection limit was 10 nl or a total of 5 × 10?9 GU. In the range 20–125 nl, precision was ±10%. 相似文献
19.
Lifetable demography and reproductive traits of a Kenyan strain of the rotifer Brachionus angularis were investigated using individual and small batch culture approaches. The rotifer was identified morphologically before conducting studies at 20, 25 and 30 °C, using Chlorella vulgaris at 2.5 × 105 to 2.5 × 107 cells ml–1. The rotifers were highly fecund, producing 2.11 ± 0.07 offspring female–1 day–1 and reproductive, producing 8.43 ± 0.24 offspring female–1 at 25 °C with 2.5 × 106 algal cells ml–1. The highest intrinsic rate of natural increase (0.74 ± 0.02 d–1), specific population growth rate (0.49 ± 0.01), longest life expectancy at hatching (12.41 ± 0.28 d) and shortest generation time (2.87 ± 0.03 d) also occurred at 25 °C with 2.5 × 106 algal cells ml–1. The duration of hatching to first spawning was shortest (2.86 ± 0.21 h) at 30 °C with 2.5 × 107 algal cells ml–1 and longest (8.83 ± 0.39 h) at 20 °C with 2.5 × 105 algal cells ml–1. The highest population density (255.7 ± 12.6 ind. ml–1) was realised at 25 °C with 2.5 × 106 cells ml–1 on Day 8, whereas the lowest population density (122.0 ± 3.6 ind. ml–1) was realised at 20 °C with 2.5 × 105 cells ml–1 on Day 8. The lorica length and width of the Kenyan strain of B. angularis are 85.6 ± 3.1 µm and 75.4 ± 3.6 µm, respectively. The rotifer optimally reproduces at 25 °C when fed with 2.5 × 106 algal cells ml–1. 相似文献
20.
Effect of Anabaena flos-aquae on the abilities of Daphnia and Keratella to feed and reproduce on unicellular algae 总被引:1,自引:0,他引:1
SUMMARY.
- 1 This study tests the hypothesis that the filamentous cyanobacterium, Anabaena flos-aquae, inhibits Daphnia's ability to feed and reproduce on unicellular algae more than it does Keratella's. Double-label radiotracer experiments using whole and sonieally disrupted Anabaena filaments showed that even low concentrations of Anabaena (5 × 103 cells ml?1) inhibited the abilities of Daphnia pulex and D. galeata mendotae to feed on Chlamydomonas and that this inhibition was due to both mechanical interference with feeding and increased food availability. A single-label radiotracer experiment showed that Anabaena (5 × 103 and 2 × 104 cells ml?l) reduced the abilities of neonate, juvenile, and adult D. pulex to feed on Chlamydomonas but had a much more pronounced effect on adults.
- 2 Single-label radiotracer experiments using screened (25 μm mesh) and unscreened suspensions of whole Anabaena filaments showed that only very high concentrations of Anabaena (105 cells ml?1) reduced the ability of Keratella cochlearis to feed on Cryptomonas and that this inhibition probably was due to mechanical interference with feeding, since Keratella ate Anabaena extremely inefficiently - especially when single cells and short filaments were removed by screening.
- 3 Experiments comparing the survivorship and fecundity of individuals fed Anabaena, Chlamydomonas, or no food showed that the Anabaena was not toxic to either Keratella or D. galeata mendotae, was not utilized by Keratella, and was utilized by Daphnia, although not as well as Chlamydomonas was.
- 4 Anabaena (5 × 103 or 104 cells ml?1) did not affect, or slightly increased, the population growth rate (rm) of K. cochlearis on Cryptomonas, while it substantially increased that of D. pulex, Duphnia's ability to utilize Anabaena probably more than offset its reduced ability to feed on Cryptomonas. The presence of cyanobacterial filaments in natural plankton communities could adversely affect Daphnia and decrease its ability to competitively suppress Keratella and other rotifers if the filaments were of little nutritional value to the Daphnia, greatly interfered