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.     

Effects of dietary n-3 PUFA levels in early life on susceptibility to high-fat-diet-induced metabolic syndrome in adult mice

The maternal nutritional status during pregnancy and lactation was closely related to the growth and development of the fetus and infants, which had a profound impact on the health of the offspring. N-3 polyunsaturated fatty acid (PUFA) had been proved to have beneficial effects on glucolipid metabolism. However, the effects of dietary different n-3 PUFA levels for mother during pregnancy and lactation on susceptibility to high-fat-diet-induced metabolic syndrome for offspring in adulthood are still unclear. The maternal mice were fed with control, n-3 PUFA-deficient or fish oil-contained n-3 PUFA-rich diets during pregnancy and lactation, and the weaned offspring were fed with high-fat or low-fat diet for 13 weeks, then were subjected to oral glucose tolerance tests. The results showed that dietary n-3 PUFA-deficiency in early life could aggravate the high-fat-diet-induced glucolipid metabolism disorders, including glucose intolerance, insulin resistance, obesity, and dyslipidemia, thus increased the susceptibility to metabolic syndrome of adult mice. Notably, nutritional supplementation with n-3 PUFA in early life could significantly alleviate the glucose metabolism disorders by increasing insulin sensitivity, inhibiting gluconeogenesis and promoting glycogenesis. In addition, administration with n-3 PUFA in early life remarkably reduced serum and hepatic lipid profiles by mediating the expression of genes related to lipogenesis and β-oxidation of fatty acids. Dietary n-3 PUFA-deficiency in early life increases the susceptibility to metabolic syndrome of adult offspring, and nutritional supplementation with n-3 PUFA enhances the tolerance to a high-fat diet of adult offspring.     

Density‐Dependent Foraging and Interference Competition by Common Gartersnakes are Temperature Dependent

The ideal free distribution (IFD) predicts that optimal foragers will select foraging patches to maximize food rewards and that groups of foragers should thus be distributed between food patches in proportion to the availability of food in those patches. Because many of the underlying mechanisms of foraging are temperature dependent in ectotherms, the distribution of ectothermic foragers between food patches may similarly depend on temperature because the difference in fitness rewards between these patches may change with temperature. We tested the hypothesis that the distribution of Common Gartersnakes (Thamnophis sirtalis) between food patches can be explained by an IFD, but that conformance to an IFD weakens as temperature departs from the optimal temperature because fitness rewards, interference competition and the number of individuals foraging are highest at the optimal temperature. First, we determined the optimal temperature for foraging. Second, we examined group foraging at three temperatures and three density treatments. Search time was optimized at 27°C, handling time at 29°C and digestion time at 32°C. Gartersnakes did not match an IFD at any temperature, but their distribution did change with temperature: snakes at 20°C and at 30°C selected both food patches equally, while snakes at 25°C selected the low food patch more at low density and the high food patch more at high density. Food consumption and competition increased with temperature, and handling time decreased with temperature. Temperature therefore had a strong impact on foraging, but did not affect the IFD. Future work should examine temperature‐dependent foraging in ectotherms that are known to match an IFD.     

Accumulation of polyunsaturated fatty acids by cladocerans: effects of taxonomy,temperature and food

1. Zooplankton are important in transferring dietary nutrients, including polyunsaturated fatty acids (PUFA), up through aquatic food webs. 2. We tested the hypothesis that the taxonomic composition of zooplankton affects the retention and subsequent transfer of PUFA from upwards through the food web. Using laboratory experiments, we investigated dietary PUFA accumulation and bioconversion capacities of six cladoceran species (Ceriodaphnia sp., Daphnia longispina, Daphnia magna, Daphnia pulex, Scapholeberis mucronata and Simocephalus vetulus) fed on two diets (Scenedesmus obliquus and Cryptomonas sp.) that differed in their PUFA profiles. We performed experiments at two different temperatures (14 and 20 °C) to assess the role of temperature in the trophic transfer of PUFA. 3. There was little variation in the concentrations of PUFA in these cladocerans which were controlled by dietary PUFA supply. Moreover, as expected, the concentrations of PUFA in all cladoceran species were higher at low temperature. 4. However, even if the composition of PUFA in the cladoceran species generally corresponded to that in their diet, preferential accumulation of some PUFA was recorded in all these taxa. When fed on a highly unsaturated fatty acid‐deficient diet, all the cladocerans showed some ability to convert C18‐PUFA into arachidonic acid and eicosapentaenoic acid. Interspecific variation in the ability to accumulate and bioconvert PUFA in cladocerans was more pronounced at low temperature (14 °C) for both diets. 5. Our results strongly suggest that in heterogeneous habitats with food partitioning between co‐existing cladocerans, foraging behaviour may affect the transfer of PUFA more strongly than interspecific variation in accumulating and/or bioconverting dietary PUFA.     

Temperature effects on egg size and their fitness consequences in the yellow dung fly Scathophaga stercoraria

Organisms and parts of an organism like eggs or individual cells developing in colder environments tend to grow bigger. A unifying explanation for this Bergmann's rule extended to ectotherms has not been found, and whether this is an adaptive response or a physiological constraint is debated. The dependence of egg and clutch size on the mother's temperature environment were investigated in the yellow dung fly Scathophaga stercoraria. Smaller eggs were laid at warmer temperatures in the field and the laboratory, where possible confounding variables were controlled for. As clutch size at the same time was unaffected by temperature, this effect was not due to a trade-off between egg size and number. Temperature-dependent egg sizes even persisted within individuals: when females were transferred to a cooler (warmer) environment, they laid third-clutch eggs that were larger (smaller) than their first-clutch eggs. The fitness consequences of these temperature-mediated egg sizes were further investigated in two laboratory experiments. Neither egg and pre-adult survivorship nor larval growth rate were maximized, nor was development time minimized, at the ambient temperature corresponding to the mother's temperature environment. This does not support the beneficial acclimation hypothesis. Instead, this study yielded some, but by no means conclusive indications of best performance by offspring from eggs laid at intermediate temperatures, weakly supporting the optimal temperature hypothesis. In one experiment the smaller eggs laid at 24 °C had reduced survivorship at all ambient temperatures tested. Smaller eggs thus generally performed poorly. The most parsimonious interpretation of these results is that temperature-mediated variation in egg size is a maternal physiological response (perhaps even a constraint) of unclear adaptive value. This revised version was published online in November 2006 with corrections to the Cover Date.     

BERGMANN SIZE CLINES: A SIMPLE EXPLANATION FOR THEIR OCCURRENCE IN ECTOTHERMS

In general ectothermic organisms grow larger at both lower temperatures and higher latitudes. Adult size in the soil nematode Caenorhabditis elegans reared at 10°C was approximately 33% greater than worms grown at 25°C. Nematode egg size and fish red blood cell size showed similar size increases at lower temperatures. These results indicate that body size differences in many ectotherms may simply be a consequence of developmental processes that cause cells to grow larger at lower temperatures. This would provide a general explanation for the increased size of ectotherms at lower temperatures independent of species-specific ecology.     

Gene identification and functional characterization of a Δ12 fatty acid desaturase in Tetrahymena thermophila and its influence in homeoviscous adaptation to low temperature

Homeoviscous adaptation in poikilotherms is based in the regulation of the level of desaturation of fatty acids, variation in phospholipids head groups and sterol content in the membrane lipids, in order to maintain the membrane fluidity in response to changes in environmental temperature. Increased proportion of unsaturated fatty acids is thought to be the main response to low-temperature acclimation, which is mostly achieved by fatty acid desaturases. Genome analysis of the ciliate Tetrahymena thermophila and a gene knockout approach has allowed us to identify one Δ12 FAD and to study its activity in the original host and in a yeast heterologous expression system. The “PUFA index” -relative content of polyunsaturated fatty acids compared to the sum of saturated and monounsaturated fatty acid content- was ~57% lower at 15 °C and 35 °C in the Δ12 FAD gene knockout strain (KOΔ12) compared to WT strain. We characterized the role of T. thermophila Δ12 FAD on homeoviscous adaptation and analyzed its involvement in cellular growth, cold stress response, and membrane fluidity, as well as its expression pattern during temperature shifts. Although these alterations allowed normal growth in the KOΔ12 strain at 30 °C or higher temperatures, growth was impaired at temperatures of 20 °C or lower, where homeoviscous adaptation is impaired. These results stress the importance of Δ12 FAD in the regulation of cold adaptation processes, as well as the suitability of T. thermophila as a valuable model to investigate the regulation of membrane lipids and evolutionary conservation and divergence of the underlying mechanisms.     

Growth and reproduction of the mosquitofish,Gambusia affinis,in relation to temperature and ration level: consequences for life history

The allocation of energy to growth and reproduction, in relation to temperature and food availability, was investigated in laboratory experiments with the mosquitofish,Gambusia affinis. At constant temperature of 20, 25 and 30°C and ad libitum feeding, specific growth rates increased with increasing temperature at 1.7, 3.1 and 3.4% dry mass day⁻¹, respectively. Growth rates in a cycling temperature regime (20–30°C, ) were faster than in a 25°C constant temperature. As temperature increased from 20 to 30°C, mean age at first reproduction decreased from 191 to 56 days and brood size and mass of offspring increased significantly. Interbrood interval was also temperature dependent; estimates at 25 and 30°C for females >1000 mg were 22.6 and 18.6 days, respectively. Interbrood interval could not be calculated at 20°C. Although fitness was highest at 30°C, females at 25°C invested a greater proportion of surplus energy (growth and reproduction) to reproduction (38%) than at 20 (17%) or 30°C (36%) during the 32-week study. Fish at cooler temperatures began reproduction at a smaller size. Where rations were controlled at low, medium, and ad libitum levels, somatic and gonadal growth increased with increasing temperatures and food availability. The proportion of energy invested in reproduction was highest at 25°C for each comparable ration level. Calculated energy budgets indicated that over the 10-week study, 17–22% of the food energy was invested in growth, 0–7% in reproduction, and 75–83% in respiration and excretory losses, depending on feeding and temperature conditions.     

Combined effects of temperature and food concentration on growth and reproduction of Eodiaptomus japonicus (Copepoda: Calanoida) from Lake Biwa (Japan)

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Leptin promotes the fat preference associated with low-temperature acclimation in mice

ABSTRACT

Although fluctuations in energy metabolism are known to influence intake as well as nutrient selection, there are no definitive reports on how food preferences change with changes in habitat temperature. We investigated the effects of habitat temperature on appetite and food preference and elucidated the underlying mechanism by conducting a feeding experiment and a leptin administration test on mice reared at low temperatures. Our results showed that the increased food intake and HFD preference observed in the 10°C group were induced by decrease in plasma leptin concentration. Then, a leptin administration experiment was conducted to clarify the relationship between leptin and food preference with low-temperature acclimation. The control group reared in 10°C significantly preferred the HFD, but the leptin-administered group did not. These results show that the peripheral system appetite-regulating hormone leptin not only acts to suppress appetite but also might inhibit preference for lipids in low-temperature acclimation.     

Fatty acid composition in the white muscle of Cottoidei fishes of Lake Baikal reflects their habitat depth

Lake Baikal is a unique freshwater environment with maximum depths over 1600 m. The high water pressure at the lakebed strengthens the solidifying effect of low water temperature on animal tissue lipids, and thus the effective temperatures in the depths of the lake equal subzero temperatures in shallow waters. Cottoidei species has colonized the different water layers of the lake, and developed different ecology and physiology reflected in their tissue biochemistry. We studied by gas chromatography the composition of fatty acids (FAs), largely responsible for tissue lipid physical properties, in the white muscle tissue of 13 species of the Cottoidei fish; five benthic abyssal, six benthic eurybathic and two benthopelagic species. The FA profiles reflected habitat depth. The muscles of the deepest living species contained little polyunsaturated FAs (PUFAs) and were instead rich in monounsaturated FAs (MUFAs), which may be due to occasional weak food web links to the PUFA-rich primary producers of the photic water layer, high MUFA supply from their benthic diet, and conversion of saturated FAs (SFAs) to MUFAs in the tissues of the fish. Despite the MUFA percentage among the abyssal species reached even 50% (by weight) of total FAs, the PUFA percentage still remained above 20% in every species. The muscle MUFA/SFA ratio correlated negatively with the PUFA content of the fish muscle, suggesting viscosity control integrating the fluidity contributions from the dietary PUFAs and potentially endogenous MUFAs.     

Life history responses of the cabbage beetle Colaphellus bowringi to temperature change

Temperature is considered one of the most important mediators of phenotypic plasticity in ectotherms. Here, we investigated life history traits of the cabbage beetle, Colaphellus bowringi Baly (Coleoptera: Chrysomelidae), at a wide range of temperatures (16, 19, 22, 24, 26 and 28°C). The larval and pupal times were significantly decreased with increasing rearing temperature and growth rate was positively correlated with temperature. However, the relationship between body size and rearing temperature in C. bowringi did not follow the temperature–size rule; both males and females reached the highest body weight at 19°C. Females were significantly larger than males at all temperatures. Male pupae lost significantly more weight at metamorphosis compared to females. However, diapausing males gained significantly higher weight after feeding compared to diapausing females at higher temperatures of 22, 24, 26 and 28°C. Body weight tended to decrease with increasing rearing temperature, whereas sexual size dimorphism (SSD) tended to increase with increasing rearing temperature; thus, Rensch's rule is upheld. The degree to which SSD changed with temperature varied with different development stages. SSD was lowest in pupae, highest in newly emerged adults and intermediate in diapausing adults.     

Sterol and Fatty Acid Metabolism in Fusarium oxysporum

The effects of temperatures ranging from 10°C to 35°C on sterol and fatty acid production and hydroxymethylglutaryl CoA reductase (EC 1.1,1.34, HMGCoA reductase) activity have been examined. Growth, based on dry weight, was maximal at 25°C to 30°C. Sterol production and the reductase activity were highest at 15°C after 28~32 hr incubation when the total fatty acids were minimal. Fatty acid unsaturation generally increased with decrease in temperature.     

Breaking the temperature-size rule: Thermal effects on growth,development and fecundity of a crustacean from temporary waters

The temperature-size rule (TSR) is a well-established phenomenon to describe the growth response of ectotherms to temperature by which individuals maintained at low temperatures grow more slowly, but attain a larger size upon maturity. Although there are adaptive and non-adaptive theories about the plasticity of body size in response to temperature, these cannot be applied to all ectotherms, and little is known about the changes in growth and development rates through ontogeny. The ostracod species Heterocypris bosniaca, an inhabitant of freshwater temporary ponds, was used to examine the growth and development rates of its nine growth stages and female fecundity at four different temperatures (15 °C, 20 °C, 25 °C and 30 °C). The development rate of this species accelerates with increasing temperature, reaching a maximum value at 25 °C. The growth factor has a reverse-TSR in younger instars, and the typical TSR is followed only in the last two moults, resulting in non-monotonic response of adult size to temperature. Fecundity (total offspring per female) was not directly related to adult size and was generally higher at lower temperatures. Our results agree with recent research showing that the TSR may vary during ontogeny, and may not be a general trend in ostracod species from temporary waters. Indeed, adult carapace size seems to follow the pattern of a thermal reaction norm, probably influenced by the reduction of oxygen bioavailability at low temperature and the drastic increase in metabolic demand at the upper extreme of the thermal gradient.     

Evolution of alternative foraging tactics driven by water temperature and physiological constraints in an amphibious snake

Amphibious predatory ectotherms live and forage in two environments (aquatic and terrestrial) that can drastically differ in temperature means and variance across space and time. The locomotor performance of ectotherms is known to be strongly affected by temperature. However, how differences in water temperature may drive the evolution of alternative foraging tactics in amphibious animals remains poorly understood. Fish‐eating Viperine snakes Natrix maura occur from high altitude cold water streams to warm shallow lakes, and employ two main feeding strategies: sentinel foraging (underwater sit‐and‐wait behaviour) and active foraging (fish chasing). Using 272 juvenile snakes we measured: the performance kinetics of diving and swimming in a wide range of water temperatures; basal metabolic levels in relation to body temperature; and the type of foraging mode expressed in water‐temperature‐acclimated snakes. Individual swimming performances increased with testing temperature (10, 15, 20, 25 or 30 °C). Apnoea time followed an opposite trend however, plausibly reflecting the fact that oxygen demands are related to the metabolic rate of ectotherms. That is, snake heart rates increased with body temperature. Snakes acclimated to 10 °C water mostly displayed sentinel foraging. By contrast, 20 °C and 30 °C water‐acclimated snakes were extremely active fish chasers. Individual apnoea times at the various testing temperatures were all correlated; as were individual swimming speeds. There was however no clear relationship between an individual's ability to hold its breath and its ability to swim, suggesting that both performance traits may be the target of different selective pressures. Fast swimming speed and long breath holding abilities are likely key determinants of both foraging success and predatory evasion, although in a context dependent manner. Active swimming foraging is likely to be advantageous in warm water (> 20 °C), while sentinel foraging appears better suited to cold water (< 14 °C). The physiological aspects of foraging tactics of amphibious snakes combined with field and laboratory observations support the idea that physiological and environmental constraints may generate shifts in habitat use and associated foraging tactics in amphibious ectotherms. Avenues for further research are discussed. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 411–422.     

Effects of temperature on food ingestion rate and absorption,retention, and equilibrium burden of phosphorus in an aquatic snail,Goniobasis clavaeformis Lea *

The effects of sublethal temperatures on feeding rates and phosphorus dynamics of a freshwater snail, Goniobasis clavaeformis Lea, were determined and feeding rates were measured at four temperatures. The food source was aufwuchs labelled with radioactive phosphorus. A model was developed to elucidate the results of this type of study. Food ingestion rate increased with increasing temperature up to 14°C and then decreased at temperatures above 14°C. The elimination rate of absorbed phosphorus increased with increasing temperature throughout the entire range of experimental temperatures, 10-19.3°C. Mean retention times of absorbed phosphorus i n Goniobasis were estimated to be 34, 24, 10, and 6 days at 10, 13.8, 15, and 193°C, respectively. Mean retention time of unabsorbed ³²P in the gut of this species as a function of temperature followed the same temperature relationship as that of ingestion rate. The absorption efficiency of phosphorus was estimated to be constant at about 39% for ail experimental temperatures, although the data suggest that the absorption ePRciency may have been related inversely to the rate of gut clearance or directly to the residence time of food in the gut. The equilibrium body load of phosphorus at each experimental temperature was estimated based on concentrations of stable phosphorus in the food source and the kinetics of ³²P in Goniobasis. The equilibrium body burden of phosphorus in Goniobasis increased with increasing temperatures up to a maximum at 11–12°C and then decreased at temperatures above 12°C.     

WITHIN- AND BETWEEN-GENERATION EFFECTS OF TEMPERATURE ON THE MORPHOLOGY AND PHYSIOLOGY OF DROSOPHILA MELANOGASTER

We investigated the effects of developmental and parental temperatures on several physiological and morphological traits of adult Drosophila melanogaster. Flies for the parental generation were raised at either low or moderate temperature (18°C or 25°C) and then mated in the four possible sex-by-parental temperature crosses. Their offspring were raised at either 18°C or 25°C and then scored as adults for morphological (dry body mass, wing size, and abdominal melanization [females only]), physiological (knock-down temperature, and thermal dependence of walking speed), and life history (egg size) traits. The experiment was replicated, and the factorial design allows us to determine whether and how paternal, maternal, and developmental temperatures (as well as offspring sex) influence the various traits. Sex and developmental temperature had major effects on all traits. Females had larger bodies and wings, higher knock-down temperatures, and slower speeds (but similar shaped performance curves) than males. Development at 25°C (versus at 18°C) increased knock-down temperature, increased maximal speed and thermal performance breadth, decreased the optimal temperature for walking, decreased body mass and wing size, reduced abdominal melanization, and reduced egg size. Parental temperatures influenced a few traits, but the effects were generally small relative to those of sex or developmental temperature. Flies whose mother had been raised at 25°C (versus at 18°C) had slightly higher knock-down temperature and smaller body mass. Flies whose father had been raised at 25°C had relatively longer wings. The effects of paternal, maternal, and developmental temperatures sometimes differed in direction. The existence of significant within- and between-generation effects suggests that comparative studies need to standardize thermal environments for at least two generations, that attempts to estimate “field” heritabilities may be unreliable for some traits, and that predictions of short-term evolutionary responses to selection will be difficult.     

Phytoplankton sterol contents vary with temperature,phosphorus and silicate supply: a study on three freshwater species

The understanding of environmentally induced changes in the biochemical composition of phytoplankton species is of great importance in both physiological studies and ecological food web research. In extensive laboratory experiments we tested the influence of two different temperatures (10°C and 25°C) and a phosphorus supply gradient on the sterol concentrations of the three freshwater phytoplankton species Scenedesmus quadricauda, Cryptomonas ovata and Cyclotella meneghiniana. The diatom C. meneghiniana was additionally exposed to a silicate gradient. In two separate experiments we analysed (1) possible interactive effects of temperature and phosphorus supply and (2) the effect of four phosphorus levels and three silicate levels on algal sterol concentrations. We observed that sterol concentrations were higher at 25°C than at 10°C in S. quadricauda and C. meneghiniana, but were not affected by temperature in C. ovata. Interactive effects of temperature and phosphorus supply on sterol concentrations were found in C. meneghiniana. This presumably was due to the bioconversion of one sterol (24-methylenecholesterol) into another (22-dihydrobrassicasterol). Increasing phosphorus supply resulted in species-specific effects on sterol concentrations, viz. an optimum curve response in S. quadricauda, a saturation curve response in C. meneghiniana and no change in sterol concentration in C. ovata. Effects of silicate supply on the sterols of C. meneghiniana equalled the effects of phosphorus supply. Albeit we did not observe a general trend in the three phytoplankton species tested, we conclude that sterol concentrations of phytoplankton are strongly affected by temperature and nutrient supply. Interactive effects point out the importance of taking into account more than just one environmental factor when assessing the effects of environmentally induced changes on phytoplankton sterol concentrations.     

Temperature-dependent effect of food size on the reproductive performances of the small-sized cladoceran Moina micrura

To determine the combined effects of temperature and minimal change in food size on small-sized cladocerans, we fed Moina micrura with unicells and small colonies of Scenedesmus obliquus at different temperatures (20, 25, and 30 °C) and evaluated the parameters related to development and reproduction. Results showed that development to maturity was not affected by food sizes but significantly promoted by increasing temperature. The number of broods and total offspring significantly increased at 30 °C when M. micrura fed on unicellular S. obliquus but was not significantly different among the three temperatures when fed on colonial S. obliquus, i.e. only at 30 °C, the reproductive performance of M. micrura fed on unicellular S. obliquus was significantly higher than those fed on colonial S. obliquus, indicating that the effect of food size on the reproductive performances of M. micrura is dependent on temperature.