Effect of food conditions on the bacterial feeding of Daphnia galeata

Feeding selectivities of Daphnia galeata were measured using various density combinations of ¹⁴C-labeled Chlamydomonas and ³H-labeled natural bacteria. In all food combinations, D. galeata preferred algae. Selectivity coefficient (bacterial clearance rate: algal clearance rate) was 0.35 at the level of incipient food limitation (1.5 × 10⁶ µm³ ml^–1).However, it increased up to 0.9 with increasing total food concentration. A simple mechanical sieving model alone cannot explain such a change in the selectivity coefficient. A mechanism of clogging suggestively explain the increase of bacterial ingestion efficiency by D. galeata, especially at high food concentrations. The change of selectivity coefficient related to food condition suggests that bacterial feeding by the Daphnia is incidental event associated with the algal feeding.     

Indirect effect of planktivorous fish on the growth and reproduction of Daphnia galeata

Both the size of Daphnia galeata primiparae and the average egg volume were smaller in individuals reared from neonata in water inhabited for the preceding 24 hours by Y-O-Y roach when compared with control animals reared in the same water with the exclusion of fish. The smaller size of experimental primiparae resulted from smaller increments in some instars and from the earlier maturation of about two-thirds of those that matured in the 4th instar, while the rest of the experimental animals and all the controls matured in the 5th instar. There were larger clutches and smaller eggs in experimentals when compared with the similar sized controls, but the difference hasn't proved to be statistically significant.     

Effects of supplementation with fish oil and barium selenate on performance, carcass characteristics and muscle fatty acid composition of late season lamb finished on grass-based or concentrate-based diets

The objectives of this study were to investigate the effects of fish oil supplementation on performance and muscle fatty acid composition of hill lambs finished on grass-based or concentrate-based diets, and to examine the interaction with selenium (Se) status. In September 2006, 180 entire male lambs of mixed breeds were sourced from six hill farms after weaning and finished on five dietary treatments: grazed grass (GG), grass +0.4 kg/day cereal-based concentrate (GC), grass +0.4 kg/day cereal-based concentrate enriched with fish oil (GF), ad libitum cereal-based concentrate (HC) and ad libitum fish oil-enriched concentrate (HF). Within each treatment, half of the lambs were also supplemented with barium selenate by subcutaneous injection. At the start of the trial, the proportion of lambs with a marginal (<0.76 μmol/l) or deficient (<0.38 μmol/l) plasma Se status was 0.84 and 0.39, respectively. Compared with control lambs, GG lambs treated with Se had higher (P < 0.01) plasma Se levels, whereas erythrocyte glutathione peroxidase activity was higher (P < 0.01) for Se-supplemented lambs fed diets GG and GF. However, Se supplementation had no effects on any aspect of animal performance. Fish oil increased (P < 0.05) levels of 22:5n-3 and 22:6n-3 in the Longissimus dorsi of HF lambs but otherwise had no effect on the health attributes of lamb meat. There were no significant effects of fish oil on dry matter intake, animal performance or lamb carcass characteristics. Daily carcass weight gain (CWG; P < 0.001), carcass weight (P < 0.01) and conformation score (P < 0.01) increased with increasing concentrate inputs. Lambs fed concentrate-based diets achieved a higher mean CWG (P < 0.001), dressing proportion (P < 0.001) and carcass weight (P < 0.011), and were slaughtered up to 8.3 days earlier (P < 0.05) and at 1.2 kg lower (P < 0.05) live weight than pasture-fed lambs. However, carcasses from grass-fed lambs contained lower levels of perinephric and retroperitoneal fat (P < 0.05), and had less fat over the Iliocostalis thoracis (P < 0.001) and Obliquus internus abdominis (P < 0.05). Meat from grass-fed lambs also had lower levels of 18:2n-6 and total n-6 fatty acids compared with those finished indoors. The results of this study demonstrate that fish oil supplementation has some benefits for the health attributes of meat from lambs fed concentrate-based diets but not grass-based diets. Supplementing Se-deficient lambs with barium selenate will improve Se status of lambs fed zero-concentrate diets, but has no additional benefit when lambs are already consuming their daily Se requirement from concentrates or when fish oil-enriched diets are fed.     

Effect of cultural conditions on the sterols and fatty acids of green algae

Six species of green algae were grown autotrophically, photohetrotrophically, and heterotrophically and their fatty acid and sterol compositions determined. Sterol composition was higher in autotrophic than in heterotrophic plants by a factor of from 2 to over 20 in five of the six species studied. Relative amounts of various sterols did not change significantly with cultural conditions. In five of the species studied, autotrophic growth produced a significant increase in the relative proportion of linolenic acid compared to that in heterotrophic or photoheterotrophic growth. This increase was usually accompanied by a corresponding decrease in oleic or linoleic acids or both.     

Effect of exogenous sterols on the growth and fatty acid composition of the oomycetePythium debaryanum

Exogenous ergosterol and cholesterol were found to affect the growth and lipogenesis of the oomycete fungusPythium debaryanum, which is unable to synthesize de novo steroid compounds. These sterols stimulated the growth of the fungus during its submerged cultivation in glucose-peptone medium. This was accompanied by the shortening of the lag phase, the lengthening of the period of active growth, and by a 3.7-or 4.3-fold increase in the maximum biomass in response to the addition of ergosterol or cholesterol, respectively. In the presence of ergosterol, the cellular content of polyenoic fatty acids increased, and the relative content of eicosapolyenoic fatty acids reached 31.4% of the total amount of fatty acids in cells. Conversely, cholesterol decreased the cellular content of polyenoic acids, and the relative content of eicosapolyenoic acids fell to 19.6% of the total amount of fatty acids. It may be inferred that exogenous sterols enhance the yield of pharmacologically active polyenoic acids because of the growth stimulation.     

The influence of bacteria-dominated diets on Daphnia magna somatic growth, reproduction, and lipid composition

We explored how dietary bacteria affect the life history traits and biochemical composition of Daphnia magna, using three bacteria taxa with very different lipid composition. Our objectives were to (1) examine whether and how bacteria-dominated diets affect Daphnia survival, growth, and fecundity, (2) see whether bacteria-specific fatty acid (FA) biomarkers accrued in Daphnia lipids, and (3) explore the quantitative relationship between bacteria availability in Daphnia diets and the amounts of bacterial FA in their lipids. Daphnia were fed monospecific and mixed diets of heterotrophic (Micrococcus luteus) or methanotrophic bacteria (Methylomonas methanica and Methylosinus trichosporium) and two phytoplankton species (Cryptomonas ozolinii and Scenedesmus obliquus). Daphnia neonates fed pure bacteria diets died after 6-12?days and produced no viable offspring, whereas those fed pure phytoplankton diets had high survival, growth, and reproduction success. Daphnia fed a mixed diet with 80% M.?luteus and 20% of either phytoplankton had high somatic growth, but low reproduction. Conversely, Daphnia fed mixed diets including 80% of either methane-oxidizing bacteria and 20% Cryptomonas had high reproduction rates, but low somatic growth. All Daphnia fed mixed bacteria and phytoplankton diets had strong evidence of both bacteria- and phytoplankton-specific FA biomarkers in their lipids. FA mixing model calculations indicated that Daphnia that received 80% of their carbon from bacteria assimilated 46?±?25% of their FA from this source. A bacteria-phytoplankton gradient experiment showed a strong positive correlation between the proportions of the bacterial FA in the Daphnia and their diet, indicating that bacterial utilization can be traced in this keystone consumer using FA biomarkers.     

Application of individual growth and population models of Daphnia pulex to Daphnia magna, Daphnia galeata and Bosmina longirostris

Daphnia models for individual growth and population dynamics have been developed in the manner of models developed by Gurney, McCauley, Andersen and others. All or most of the earlier models were parameterized for Daphnia pulex; we have used the D. pulex model as a baseline model for other species of Daphnia such as magna, galeata and also Bosmina longirostris. Because of the lack of ample data for D. magna, D. galeata and B. longirostris, some of the physiological data had to be relied on the other species whose data were available and in some case calibrated. We were able to produce reasonable results for individual growth as well as population dynamics under the controlled laboratory conditions. Most of the results were compared with the available laboratory data for population as well as growth. All the simulations have been done under high and low food concentrations. The animals are assumed to be feeding on green algae (Chlamydomonas reinhardtti) under the laboratory conditions of 18–20°C. The continuous growth until the end of the life was observed in smaller B. longirostris, whereas rapid growth in the beginning and slower after the start of the reproduction was observed in Daphnia species. The smaller species matured earlier than larger species. B. longirostris population sustained better than Daphnia species in medium food concentrations.     

Temperature affects the limitation of Daphnia magna by eicosapentaenoic acid,and the fatty acid composition of body tissue and eggs

1. Poikilothermic animals incorporate more polyunsaturated fatty acids (PUFAs) into their cellular membranes as temperature declines, suggesting an increased sensitivity to PUFA limitation in cool conditions. To test this we raised Daphnia magna at different temperatures and investigated the effect of varying dietary PUFA on life history parameters (i.e. growth, reproduction) and the PUFA composition of body tissue and eggs. 2. Upon a PUFA‐rich diet (Cryptomonas sp.) females showed higher concentrations of several ω3 PUFAs in their body tissue at 15 °C than at 20 °C and 25 °C, indicating a greater structural requirement for ω3 PUFAs at low temperature. Their eggs had an equal but higher concentration of ω3 PUFAs than their body tissue. 3. In a life history experiment at 15 and 20 °C we supplemented a diet of a PUFA‐free cyanobacterium with the ω3 PUFA eicosapentaenoic acid (EPA). The growth of D. magna was more strongly EPA limited at low temperature. A greater requirement for structural EPA at 15 °C was indicated by a steeper increase in somatic EPA content with dietary EPA compared to 20 °C. 4. At 20 °C the development of eggs to successful hatching was high when EPA was supplied to the mothers. At 15 °C the hatching success was generally poor, despite of a higher maternal provision of EPA to eggs, compared to that at 20 °C, suggesting that EPA alone was insufficient for proper neonatal development at the low temperature. The growth of offspring from mothers raised at 20 °C without EPA supplementation was very low, indicating that the negative effects of EPA deficiency can be carried on to the next generation. 5. The fatty acid composition of Daphnia sp. in published field studies shows increasing proportions of saturated fatty acids with increasing environmental temperature, whereas ω3 PUFAs and EPA show no clear pattern, suggesting that variations in dietary PUFA may mask temperature‐dependent adjustments in ω3 PUFA concentrations of cladocerans in nature.     

A comparison of the trophic transfer of fatty acids in freshwater plankton by cladocerans and calanoid copepods

1. Analyses of zooplankton fatty acid (FA) composition in laboratory experiments and samples collected from lakes in New Zealand spanning a wide gradient of productivity were used to assess the extent to which FAs might infer their diet. We used the cladocerans, Daphnia and Ceriodaphnia, and the calanoid copepod, Boeckella, as test organisms, and monocultures of cryptophytes, chlorophytes and cyanobacteria as food. Based on reproductive success, cryptophytes were the highest food quality, chlorophytes were intermediate and cyanobacteria the poorest. 2. Several FA groups were highly correlated between zooplankton and their diets. They were monounsaturated fatty acids (MUFAs), and ω3 and ω6 polyunsaturated fatty acids (PUFAs) for cladocerans, and saturated fatty acids (SAFAs) and ω3 PUFAs for copepods. Several FAs varied significantly less in the zooplankton than in their monoculture diets, e.g. MUFAs in Daphnia, and ω3 and ω6 PUFAs in Ceriodaphnia, despite clear dietary dependency for these FAs. 3. Zooplankton collected from lakes in New Zealand had more eicosapentaenoic acid (EPA) (Daphnia), more highly unsaturated ω3 and ω6 FAs (C₂₀, C₂₂; Daphnia, Ceriodaphnia, Boeckella) and less ω3 C₁₈ PUFAs (Daphnia, Ceriodaphnia, Boeckella) and ω6 C₁₈ PUFAs (Daphnia, Ceriodaphnia) than measured in the same species reared on phytoplankton in the laboratory. 4. Analyses of FA composition of seston and freshwater zooplankton globally showed that, in general, zooplankton had a significantly higher proportion of arachidonic acid and EPA than seston, and copepods also had a higher percentage of docosahexaenoic acid than seston. 5. These results suggest that zooplankton selectively incorporate the most physiologically important FAs. This could be a consequence of preferential assimilation, selective feeding on more nutritious cells or locating and feeding within higher food quality food patches.     

Effects of dietary menhaden oil on growth and reproduction in gilts farrowed by sows that consumed diets containing menhaden oil during gestation and lactation

In sows, n-3 fatty acids increase litter sizes, however, effects on gilt reproductive development have not been adequately studied. Moreover, not determined are effects of feeding n-3 fatty acids to sows on reproduction in offspring. The objective here was to determine effects of 4% dietary menhaden oil on growth and puberty in gilts farrowed by sows fed menhaden oil. Sows (n = 44) were assigned to: (1) control gestation and lactation diets, or (2) diets including menhaden oil. For primiparous sows only, total litter size and born alive were greater (P < 0.05) in females fed menhaden oil. Conversely, pigs from primiparous controls were heavier (P < 0.05) than pigs from primiparous sows fed menhaden oil (parity by diet interactions, P < 0.01). Diet did not affect (P > 0.20) other sow and litter characteristics. At weaning, 84 gilts from control- or menhaden oil sows were placed three gilts per pen and provided control diets or diets containing menhaden oil. Nursery and grow-finish feed intake and feed efficiency were similar (P > 0.21) for gilts from the different sows and weight gain was similar (P > 0.24) for gilts fed control or menhaden diets. Gilts fed menhaden oil tended to eat less in the nursery (1.18±0.08 kg v. 0.98±0.08 kg; P = 0.09) and overall (1.83±0.04 kg v. 1.72±0.04 kg; P = 0.06). Thus, overall feed to gain was greater (2.52±0.03 v. 2.33±0.03; P < 0.01) and nursery (2.12±0.04 v. 1.80±0.04; P = 0.10) and grow-finish (3.07±0.19 v. 2.58±0.19; P = 0.08) feed to gain tended to be greater, for control gilts. Age at puberty was greater (P = 0.02) for gilts from menhaden oil-fed sows (205.1±3.2 days) compared to gilts from controls (193.9±3.2 days) and tended to be greater (P = 0.09), for controls (203.5±3.2 days) compared to gilts fed menhaden oil (195.5±3.2 days). A tendency existed (P = 0.09) for greater follicular fluid in gilts fed menhaden oil, however, ovulation rate and ovarian, luteal and uterine weights were not affected by sow diet, gilt diet or the interaction (P > 0.23). Feeding gilts menhaden oil enhanced feed efficiency and hastened puberty onset. Gilts from sows consuming menhaden oil exhibited delayed puberty and retaining females from sows fed this feedstuff may be ill advised.     

Growth and reproduction of fungal feeding Collembola as affected by fungal species,melanin and mixed diets

Fungal feeding soil invertebrates feed on a wide spectrum of fungal species suggesting that mixed diets increase fitness. We investigated relationships between food preferences for seven saprophytic fungal species/forms and fitness parameters (mortality, growth, time to reproduction, reproduction, egg size) in two Collembola species, Folsomia candida and Protaphorura armata. The fungal species/forms studied included the wild type and a melanin-deficient form of Aspergillus fumigatus to investigate the role of melanin in collembolan nutrition. Also, three mixed diets consisting of a preferred fungal species (Cladosporium cladosporioides) and species of intermediate or low food quality were investigated. Both Collembola species preferred similar fungal species/forms as food. Food preference generally matched fitness parameters, i.e. growth and reproduction of Collembola was at a maximum when feeding on preferred fungi. This was not the case for A. fumigatus. The wild type and the melanin-deficient form ranked among the least preferred fungi. Growth and reproduction of Collembola were low when feeding on the wild type but high when feeding on the melanin-deficient form indicating that the Collembola misjudged the food quality of the latter in the preference tests. The results show for the first time that genes driving melanin syntheses (pksP) strongly affect the food quality of fungi for fungal feeding invertebrates. Feeding on mixed diets generally increased growth and reproduction of Collembola except when the diets included toxic species (Penicillium sp.). The results support the nutrient balance hypothesis and also show that the detection of toxic species in the diet is important. They indicate that the widespread generalist feeding mode of Collembola maximizes fitness if toxic fungal species are avoided. The fitness parameters growth, reproduction and time until onset of reproduction were correlated closely but egg volume, which also varied with fungal diet, correlated poorly with the other fitness parameters. Variation in egg size with fungal diet shows that the diet of Collembola may have transgenerational effects.     

Influence of feeding a fish oil-containing diet to young,lean, adult dogs: effects on lipid metabolites,postprandial glycaemia and body weight

The aim of this study was to determine the effect of feeding a fish oil (FO)-containing diet on lipid and protein metabolism, postprandial glycaemia and body weight in young, lean, adult dogs. Eight female Beagles were randomly assigned to one of two isonitrogenous and isoenergetic diets, Control or FO, in a crossover design. At the beginning of the experiment and at 30 and 60 d, a baseline blood sample was collected and the dogs then were fed their daily ration. Nitrogen balance began at 07:00 h on day 63 of each experimental period and ended at 07:00 h on day 69. On day 66 of each period, a single dose (7.5 mg/kg) of ¹⁵N-glycine was administered orally to each dog via gelatin capsule. Postprandial glycaemia did not differ between treatments or among sampling days within treatment. Cholesterol concentration was increased (p < 0.05) on the Control treatment throughout the experiment when compared to values of day 0. Dogs fed the FO treatment had higher plasma triglyceride and ghrelin concentrations than those fed the Control treatment. Body weight and food intake did not differ between dietary treatments. Faecal excretion was increased (p < 0.05) in the FO treatment. Dry matter digestibility was decreased (p < 0.05) and fat digestibility tended (p < 0.10) to decrease in the FO treatment. Overall, feeding a FO-containing diet showed a protective effect against the rise of plasma cholesterol and it increased plasma ghrelin concentration. However, FO supplementation did not appear to affect protein metabolism or postprandial glycaemia in adult lean dogs.     

Effects of Dietary Fatty Acids and Exercise on Body‐Weight Regulation and Metabolism in Rats

Objective: To assess the interaction of high‐fat diets (HF) made with different dietary fatty acids and exercise on body‐weight regulation, adiposity, and metabolism. Research Methods and Procedures: Male Wistar rats born to dams fed HF diets (40% w/w) made with either fish oil (FO), soybean oil (SO), or palm oil (PO) were fed diets similar to their dams and divided randomly into exercise (EX, swimming) or sedentary control (SD) groups when they were 9 weeks old. EX lasted for 6 weeks. Twenty‐four hours after the last EX bout, fasted rats were killed by decapitation. Chemical analyses and body composition analysis were conducted. Results: The results demonstrated that different fatty acids had different effects on body weight, composition, and metabolism. SO‐fed rats gained the most weight and fat. EX reduced body weight of FO‐ and PO‐fed rats, but SO‐fed rats were still heavier and fatter than other rats. Data from SO‐ and PO‐fed rats suggested that they are insulin resistant and that EX normalized this abnormality. Of the three HF diets used, FO produced the least adverse effects compared with PO and SO. Discussion: Not only the quantity of dietary fat, but also the type of fat used, will produce different effects on body weight and metabolism. EX ameliorates the suggested insulin resistance induced in rats fed either highly saturated or n‐6 polyunsaturated fatty acids. Long‐chain n‐3 polyunsaturated fatty acids, as found in fish oil, are more beneficial than n‐6 polyunsaturated fatty acids when fed in high amounts to rats.     

Thematic review series: patient-oriented research. Dietary fat, carbohydrate, and protein: effects on plasma lipoprotein patterns

In general, under isoweight conditions, different types of dietary protein or individual amino acids have little effect on lipoprotein patterns. Dietary carbohydrate tends to increase plasma triglyceride when it displaces fat, accompanied by a decrease in HDL cholesterol concentrations. Potential differential effects of types of carbohydrate are difficult to assess because of differences in rates of absorption and confounding of dietary fiber. Saturated fatty acids increase LDL and HDL cholesterol, whereas trans fatty acids increase LDL but not HDL cholesterol. Unsaturated fatty acids decrease LDL and HDL cholesterol, polyunsaturated more so than monounsaturated. There has been considerable interest in the potential benefit of major shifts in dietary macronutrients on weight loss and lipoprotein patterns. Short-term data favor substituting protein and fat for carbohydrate, whereas long-term data have failed to show a benefit for weight loss. During an active weight loss period low-carbohydrate diets more favorably affect triglyceride and HDL and less favorably affect LDL cholesterol concentrations. Additional efforts need to be focused on gaining a better understanding of the effect of dietary macronutrient profiles on established and emerging cardiovascular disease risk factors, mechanisms for changes observed and contributors to individual variability. Such data are needed to allow reassessment and, if necessary, modification of current recommendations.     

Effect of n-3 and n-6 polyunsaturated fatty acids on hare reproductive performances

The study was carried out on 42 breeder couples (42 males and 42 females) of European brown hare (Lepus europaeus), divided into three groups fed three different experimental diets (14 couples/treatment). Two diets were supplemented with n-3 and n-6 polyunsaturated fatty acids (PUFAs; 2% of linseed oil and soybean oil, respectively) and were compared with a control diet supplemented with a monounsaturated fatty acids (2% of olive oil). During the experimental period (from 15 April to 30 September), the following parameters were recorded: days from the beginning of trial to the first parturition, parturition interval, number of parturitions, number of leverets born (alive and dead), dead during suckling, the total number of leverets weaned and feed intake per cage (of males, females and leverets until weaning). Feed intake was not influenced by treatments. In hares fed n-3 and n-6 diets, the days from the beginning of the trial to the first parturition and the parturition interval were similar and were lower compared with control group (63.1 v. 70.6 days, and 37.8 v. 40.9 days, respectively; P < 0.05). Hares from n-6 group had a higher (P < 0.05) number of parturitions per cage during the experimental period than the n-3 and control group that showed a similar value (3.00 v. 2.36, respectively). The total number of leverets born per cage and parturition in n-6 and n-3 groups increased with respect to those fed control diet (P < 0.05). The leverets' mortality rate at birth was higher in n-6 than in n-3 and control group (3.50 v. 2.17, respectively; P < 0.05). In control group, leverets' mortality rate during suckling was lower with respect to n-3 (P < 0.05) and n-6 (P < 0.05), showing the highest value for the latter (P < 0.05). In spite of this higher mortality, the number of leverets weaned per cage and parturition was higher (P < 0.05) in n-6 compared with n-3 group, being the latter higher than the control group (3.12, 2.79 and 2.43, respectively). Our results show that the dietary PUFAs, particularly n-6 supplementation, have a positive influence on the reproductive performances of the European brown hare.     

The sterol and fatty acid compositions of seven tropical seagrasses from North Queensland,Australia

The sterol and fatty acid compositions of fresh leaves of the seagrasses Cymodocea serrulata, Enhalus acoroides, Halodule uninervis, Halophila ovalis, H. ovata, H. spinulosa and Thalassia hemprichii are reported. The major fatty acids were palmitic acid, linoleic acid and linolenic acid as expected. H. ovalis and H. ovata were characterized by the relatively high abundance (ca 5%) of the acid hexadeca-7,10,13-trienoic acid (16:3<7 > ). The sterol compositions were typical of higher plants, with sitosterol and stigmasterol accounting for 60–90% of the observed sterols. 28-Isofucosterol was a major sterol (20–30%) only in the Halophila spp. Cluster analysis of the sterol composition data clearly separated the Halophila spp. from the other seagrasses and enabled the distinction of Enhalus sp. from Cymodocea, Halodule and Thalassia spp. The seagrass species were clearly separated into five chemical groups using the combined fatty acid and sterol composition data and the need for a reappraisal of the taxonomic position of Halophila was indicated.     

Effects of endosulfan on survival,growth and reproduction of Daphnia magna

1. Acute and chronic toxicity tests with endosulfan were conducted on Daphnia magna. The 24-hr static lc₅₀ was 0.62 mg/l with a coefficient of variation of 14.2%.2. The sublethal effects of 0.12, 0.15, 0.20, 0.25 and 0.31 mg/l endosulfan on the survival, reproduction and growth of D. magna were monitored for 21 days.3. The parameters used to determined the effect of the pesticide on reproduction were: mean total young per female, maximum number of broods, mean brood size, mean number of broods, mean time to first reproduction and intrinsic rate of natural increase (r).4. Growth, as measured by body length, was depressed significantly at all endosulfan concentrations tested. The highest concentrations used (0.20, 0.25 and 0.31 mg/l) caused a decrease in survival and mean total young per female, and an increase in the time to first reproduction. The intrinsic rate of natural increase (r) and the mean number of broods were decreased significantly at all the sublethal concentrations of endosulfan tested.     

Effects of fluoride on growth, reproduction and survival in Daphnia magna

The effects of waterborne fluoride (NaF) on growth, reproduction and survival in Daphnia magna were studied from subnormal to toxic concentrations in hard reconstituted water. The 24- and 48-hr EC50S for immobilization were 205 and 98 mg F (fluoride) 1(-1). Median survival times for fed and unfed Daphnia were reduced at concentrations of F above 8.9 and 10 mg F1(-1), respectively. Growth, determined as body length after 7 and 21 days, was partially inhibited at all concentrations above 3.7 mg F1(-1). Parthenogenetic reproduction was stimulated by all concentrations (dilution factor 0.5) between 0.45 X 10(-3) mg F1(-1) and 3.7 mg F1(-1) and inhibited by all concentrations above 3.7 mg F1(-1), compared to the control with no waterborne fluoride. The highest concentration with a reproduction (number of live progeny/live female) equivalent to the control after 21 days was 4.4 mg F1(-1). However, a progressive decline in reproduction between 14 and 21 days indicates a slight long-term inhibition above 0.58 mg F1(-1). The "safe" concentration equivalent to the geometric mean of NOEC or MATC for D. magna in hard water is 4.4 mg F1(-1), derived as ZEP, the Zero Equivalent Point, for reproduction after 21 days.     

Suitability of monotypic and mixed diets for Anopheles hermsi larval development

The developmental time and survival to eclosion of Anopheles hermsi Barr & Guptavanij fed monotypic and mixed diets of ten food types were examined in laboratory studies. Larvae fed monotypic diets containing animal detritus (freeze‐dried rotifers, freeze‐dried Daphnia pulicaria, and TetraMin® fish food flakes) and the mixotrophic protistan Cryptomonas ovata developed faster and survived better than larvae that were fed other monotypic diets. Survival to adulthood of larvae fed several concentrations of the diatom Planothidium (=Achnanthes) lanceolatum was poor (<13%) and larval development time was approximately twice that of larvae fed TetraMin® fish food flakes, the standard laboratory diet. Larvae fed monotypic diets containing prokaryotes (bacteria [Bacillus cereus] and cyanobacteria [Oscillatoria prolifera]) and brewer's yeast (Saccharomyces cerevisiae) failed to survive beyond the 1^st and 2^nd instar, respectively. Larvae fed only chlorophytes, single‐celled Chlamydomonas reinhardtii and filamentous Spirogyra communis, failed to complete larval development, regardless of the concentration tested. Cohorts fed a combination of food types (mixed diets) usually developed better than cohorts fed monotypic diets. Food types that failed to support complete development when fed alone often facilitated development to adulthood when fed in combination with food types containing >1% C₂₀ polyunsaturated fatty acids as total fat, but regardless of essential fatty acid content, algae that produced mucilage and filaments that sank out of the feeding zone were poor quality diets.