A comparative analysis of the fatty acid composition of sexual and asexual eggs ofDaphnia magnaand its plasticity as a function of food quality (original) (raw)
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Allocation of essential lipids in Daphnia magna during exposure to poor food quality
Functional Ecology, 2007
In nature, food conditions change temporally and force consumers into trade-offs during resource allocation. In particular, under poor food conditions, for example during cyanobacterial blooms, herbivores have to optimize their resource allocation to maximize fitness, and face two decisions: (i) an individual might attempt to allocate acquired essential resources to reproductive tissues or use them for its own maintenance; and (ii) an individual might decide to optimize the chemical quality of its eggs. 2. As cyanobacteria feature a deficiency in some essential lipids that leads to a decline in the growth and fecundity of Daphnia , an important freshwater herbivore, we investigated Daphnia magna 's Strauss allocation of lipids such as polyunsaturated fatty acids (PUFAs) and cholesterol during an experimental non-toxic cyanobacterial bloom. 3. Generally, we found a substantial maternal investment of the particularly important omega-3 (n-3) PUFAs, in particular eicosapentaenoic acid (EPA), into the eggs. The concentration of EPA was 2·4-fold higher in eggs than in somatic tissue, a cumulative effect, which was not significantly changed under cyanobacterial food conditions. 4. Under poor conditions, D. magna not only decreased the number of eggs produced but, in principle, reduced the previously high concentrations of EPA in both eggs and somatic tissues to a similar degree. In contrast to EPA, the concentrations of α -linolenic acid and cholesterol, although lower than EPA, were more homeostatic in eggs than in somatic tissues, in which concentrations decreased. 5. When food quality was improved, D. magna were able to recover completely the fatty acid concentrations in their somatic tissues and eggs. 6. This study shows that the content of particular lipids in its food clearly affects resource allocation in D. magna , and suggests that cholesterol is important for somatic growth, while PUFAs are primarily needed for reproduction. As a decreasing investment of essential lipids into eggs implies a reduced fitness of the animals' progeny under poor food conditions, this could have a strong impact on population dynamics, which might also be valid for other species.
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.
Environmental Pollution, 2018
Analysis of the disruptive effects of chemicals on lipids in invertebrates is limited by our poor knowledge of the lipid metabolic pathways and the complete lipidome. Recent studies shown that juvenoids and bisphenol A disrupted the dynamics of lipid droplets in the crustacean Daphnia magna. This study used ultra-high performance liquid chromatography/time-of-flight mass spectrometry (UHPLC/TOFMS) to study how juvenoids (pyriproxyfen and methyl farnesoate) and bisphenol A disrupt the dynamics of glycerophospholipids and glycerolipids in Daphnia adults and their allocation to eggs. Lipidomic analysis identified 234 individual lipids corresponding to three classes of glycerolipids, seven of glycerophospholipids, and one of sphingolipids, of which 194 changed according to the chemical treatments and time. Adult females in the control and bisphenol A treatment groups had low levels of triacylglycerols but high levels of glycerophospholipids, whereas those in the juvenoid treatment groups had high levels of triacylglycerols and low levels of glycerophospholipids. The opposite trend was observed for the lipid contents in the eggs produced. Because the juvenoids reduced reproduction dramatically, the females allocated less triacylglycerols to their eggs than the controls did. Interestingly, females exposed to bisphenol A allocated less triacylglycerols to their eggs despite producing a similar number of eggs as that of the controls. Thin-layer chromatography analyses confirmed the UHPLC/TOFMS results and allowed qualitative determination of cholesterol, which was also accumulated in females exposed to the juvenoids.
Marine Biology, 2003
The impact of supplementing lipid emulsions rich in eicosapentaenoic acid (EmEPA), docosahexaenoic acid (EmDHA) or saturated fatty acids (EmCOCO) to a standard algal diet [3:1 mixture of Isochrysis galbana (T-iso) and Chaetoceros neogracile, St-diet] on Argopecten purpuratus broodstock was evaluated. Broodstock fecundity was compared as well as the egg quality in terms of lipid content, fatty acid composition and lipid class distribution. Fecundity was defined as the number of eggs released in the spawning process, since spawning was virtually complete. Results indicated that the total lipid content of the eggs of A. purpuratus was diet independent. A greater energy reserve was spent on a larger number of oocytes and not on bigger sized oocytes with a higher lipid content. The lipids supplied through the emulsions were at least partially allocated to the eggs, demonstrating that the fatty acid composition of the eggs could be manipulated, especially the neutral lipid fraction. Levels of EPA changed more rapidly than DHA levels, supporting the observation that they fulfilled an energetic and structural role, respectively. The St-diet supplemented with 50%EmCOCO resulted in a significantly higher fecundity compared to the algal diet supplemented with 25%EmEPA+25%EmDHA and the non-supplemented algal diet. It would seem that saturated fatty acids (SAFA) were more easily or preferentially incorporated in the female gonads of A. purpuratus. The relative content of SAFA and 18:2(n-6) in these eggs rose significantly. The relative content of the highly unsaturated fatty acids, EPA and DHA, on the other hand was substantially lower in the neutral lipid fraction, but hardly affected in the polar lipid fraction. It appeared that the maintenance of an adequate DHA/EPA ratio (approximately 1.2) was more important than the absolute levels of the two fatty acids, as long as a threshold value was reached.
Egg size and egg mass of Daphnia magna: response to food availability
Hydrobiologia, 1995
The influence of different food availability on egg size and egg mass in Daphnia magna Straus was studied in long-term experiments using a flow-through system . Daphnia were either kept at constant high or low food levels or subjected to alternating periods of high food and starvation . Some animals were starved continuously after they had deposited their first clutch of eggs . Eggs were measured and weighed and their density (dry mass per volume) was determined. The results support the model of Glazier (1992), which defines a region of `reproductive constraint' at very low food concentrations and a region of `adaptive response' as food concentrations increase . Egg sizes were largest under continuously low food concentrations (0 .1 mg C 1 -1 ), which indicates that the maximum of Glazier's non-linear response curve is at very low food levels . Eggs produced during starvation were small, probably as a result of reproductive constraints . Egg density was about 0 .37 mg dry weight mm -3 and did not differ between treatments .
Previous studies examining the effects of food quality on zooplankton often controlled for maternal effects of resource provisioning using standardized maternal diets. However, varying nutritional history of mothers may change resource provisioning to their progeny, especially regarding polyunsaturated fatty acids (PUFAs), which may change the interpretation of previously observed fitness responses of offspring. To assess PUFA-mediated maternal provisioning effects on offspring, we raised females of the cladoceran Daphnia magna on diets differing considerably in PUFA composition and raised their offspring on a PUFA-lacking diet supplemented with the ω3 PUFAs α-linolenic acid (ALA) and/or eicosapentaenoic acid (EPA). The mass-specific growth responses of offspring to their own diets were affected by the maternal diet regime, probably due to varying maternal PUFA provisioning. A low maternal provisioning of EPA or ALA was sufficient to prevent growth limitation of offspring by these PUFAs until reaching maturity. A comparison with results of published ALA and EPA supplementation experiments suggests that the previously observed limitation effects depended on the usage of a single algae genus as maternal diet. Therefore, we suggest that maternal diets should be deliberately varied in future studies assessing ecological relevant food quality effects on zooplankton, especially regarding PUFAs.
Journal of Plankton Research
Nutrition bioassays in which polyunsaturated fatty acids (PUFA)-deficient diets were supplemented with free longchain PUFA (≥C20) consistently revealed positive effects on somatic growth and fecundity of Daphnia. However, free PUFA are hardly available in natural diets. In general, PUFA are bound to other lipids, especially to phospholipids and triglycerides. Here, we evaluate the potential of free and phospholipid-bound dietary eicosapentaenoic acid (EPA) to support somatic growth and fecundity of Daphnia magna. In a growth experiment, supplementation of a C20 PUFA-deficient diet with free or phospholipid-bound EPA improved somatic growth rates of D. magna equally. However, the increase in fecundity was significantly more pronounced when phospholipid-bound EPA was provided. Free and phospholipid-bound EPA were provided in the same concentrations in our experiment, suggesting that the allocation to reproduction-related processes is affected differently by phospholipid-bound PUFA and free PUFA. Our finding stresses the need to consider the distribution of dietary PUFA in different lipid classes to gain a better understanding of how PUFA influence life history traits of Daphnids in the field.
Inland Waters, 2012
Knowing when, where, and why food quality limits herbivore growth and reproduction is the core question in nutritional ecology. We investigated dietary threshold concentrations of polyunsaturated fatty acids (PUFAs) for the herbivorous zooplankter Daphnia pulex when fed the cyanobacterium Microcystis aeruginosa or the green algae Scenedesmus obliquus. Phosphatidylcholine liposomes were used to supplement diets with arachidonic acid (ARA, 20:4ω6), stearidonic acid (SDA, 18:4ω3), or eicosapentaenoic acid (EPA, 20:5ω3) at concentrations (per mg carbon) ranging from 0.04 to 10 µg (mg C) −1. ARA supplementation had no effect on Daphnia somatic growth or reproduction. SDA supplementation did not affect Daphnia growth, however egg production dropped below a 50% saturation threshold when dietary SDA concentrations were <0.34-0.39 µg SDA (mg C) −1. Daphnia egg production dropped below a 50% saturation threshold when EPA concentrations for the Microcystis and Scenedesmus treatments were <0.25 and 0.17 µg EPA (mg C) −1 , respectively. Growth declined below the 50% threshold when EPA concentrations for the 2 diets were <0.14 and 0.04 µg EPA (mg C) −1 , respectively. These results show the demands for EPA are more intense for reproduction than for somatic growth. We used the EPA results to develop an overall model between Daphnia production and dietary EPA: normalized production = (EPA/C)/(0.15 + EPA/C), R 2 = 0.72, n = 40. The bootstrapped 50% saturation threshold for this model was 0.15 ± 0.03 (± SE) µg EPA (mg C) −1. Our results suggest Daphnia pulex dietary EPA limitation may be common in eutrophic lakes.
Aquaculture Research, 2011
The present study examines the total lipid (TL) and fatty acid (FA) composition in eggs of brill Scophthalmus rhombus L. and the possible relationships with their quality parameters. Wild broodstocks were caught and maintained in captivity until eggs were collected. A lipid characterization of each egg batch was conducted in TL, lipid classes (LC) and FA of TL. The TL content was lower than the values reported for other £at¢sh species, showing high levels of sterol esters (SE). High viability rates were related to higher lipid reserves. Higher cholesterol (CHO) was linked to higher egg viability, whereas SE could have an opposite e¡ect. Comparison of female quality showed that lipid composition was more related to egg batches than to individual females. However, multivariate analysis did not show a clear correlation between lipid composition and brill egg quality, neither as individual components nor as a whole pro¢le of LC or FA. Our results suggest that some lipid components (phosphatidylcholine, CHO, SE, monounsaturated, eicosapentaenoic acid) could be related to di¡erences in spawning quality, although these were not the only factors involved in these di¡erences. Thus, these lipid components could be considered to be descriptors of the di¡erences found in the rates of brill quality.