Fatty acid profiles of yolk lipids of five species of wild ducks (Anatidae) differing in dietary preference

Japanese rock ptarmigan displays high levels of polyunsaturated fatty acid in egg yolk compared to chicken and quail

Egg yolk from captive and wild Japanese rock ptarmigan were analyzed for fatty acid composition. Compared to commercially reared poultry species, the ptarmigan yolk samples displayed higher level of polyunsaturated fatty acids as opposed to monounsaturated fatty acids. The difference between the commercial controls and ptarmigan were larger than the difference between groups of ptarmigan, indicating that the fatty acid profile of Japanese rock ptarmigan might be partly attributed to genetic factors rather than feed, despite wild and captive birds having vastly different diets, and captive birds having been artificially bred for several generations.

Lipid profiling suggests species specificity and minimal seasonal variation in Pacific Green and Hawksbill Turtle plasma

In this study, we applied multiple reaction monitoring (MRM)-profiling to explore the relative ion intensity of lipid classes in plasma samples from sea turtles in order to profile lipids relevant to sea turtle physiology and investigate how dynamic ocean environments affect these profiles. We collected plasma samples from foraging green (Chelonia mydas, n = 28) and hawksbill (Eretmochelys imbricata, n = 16) turtles live captured in North Pacific Costa Rica in 2017. From these samples, we identified 623 MRMs belonging to 10 lipid classes (sphingomyelin, phosphatidylcholine, free fatty acid, cholesteryl ester, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, phosphatidylethanolamine, ceramide, and triacylglyceride) and one metabolite group (acyl-carnitine) present in sea turtle plasma. The relative ion intensities of most lipids (80%) were consistent between species, across seasons, and were not correlated to body size or estimated sex. Of the differences we observed, the most pronounced was the differences in relative ion intensity between species. We identified 123 lipids that had species-specific relative ion intensities. While some of this variability is likely due to green and hawksbill turtles consuming different food items, we found indications of a phylogenetic component as well. Of these, we identified 47 lipids that varied by season, most belonging to the structural phospholipid classes. Overall, more lipids (n = 39) had higher relative ion intensity in the upwelling (colder) season compared to the non-upwelling season (n = 8). Further, we found more variability in hawksbill turtles than green turtles. Here, we provide the framework in which to apply future lipid profiling in the assessment of health, physiology, and behavior in endangered sea turtles.

Nutrient Profiles of Wild and Captive Attwater's and Greater Prairie-Chicken Eggs

We determined reference levels of minerals, fatty acids, and fat-soluble micronutrients in eggs from wild Attwater's Tympanuchus cupido attwateri and two (Minnesota, Nebraska) greater prairie-chicken T. c. pinnatus populations for comparison with eggs produced by captive Attwater's prairie-chickens to help guide formulation and evaluation of captive diets. Levels of all minerals found in wild Attwater's prairie-chicken eggs were similar to those in at least one of the two greater prairie-chicken populations, but these levels frequently differed between the two greater prairie-chicken populations. Ratios for n-6:n-3 fatty acids were >3 times higher for Minnesota greater prairie-chickens, which had more access to waste grain than Attwater's or Nebraska greater prairie-chickens. Captive eggs had n-6:n-3 ratios 6.7 times the pooled wild samples, while wild eggs had higher levels of anhydrolutein, zeaxanthin, β-carotene, and total carotenoids. More magnesium, zinc, and manganese were observed in wild eggs compared with those produced in captivity. Flaxseed was added to the captive breeder diet in an attempt to lower egg n-6:n-3 ratios, along with additional carotenoids found in marigold extract. These dietary modifications successfully lowered the n-6:n-3 ratio by 46%, but this ratio was still 3.6 times higher in captive eggs, consistent with the grain-based formulation of the breeder diet. Carotenoid additions successfully raised total carotenoids, but increases were primarily for lutein and not zeaxanthin or β-carotene as intended. Variability in egg nutrient composition among the three wild populations suggests that some tolerance exists in maternal diets, but impacts to offspring fitness are unknown. Given the purported importance of maternal nutrition to fitness of embryos and neonate chicks, we suggest additional research is needed to quantify the influence of key nutrient levels on offspring fitness for both captive and wild populations.

Mechanisms of reproductive allocation as drivers of developmental plasticity in reptiles

Developmental plasticity in offspring phenotype occurs as a result of the environmental conditions embryos experience during development. The nutritional environment provided to a fetus is an important source of developmental plasticity. Reptiles are a particularly interesting system to study this plasticity because of their varied routes of maternal nutrient allocation to reproduction. Most reptiles provide their offspring with all or most of the nutrients they require in egg yolk (lecithotrophy) while viviparous reptiles also provide their offspring with nutrients via a placenta (placentotrophy). We review the ways in which both lecithotrophy and placentotrophy can lead to differences in the nutrients embryonic reptiles receive, and discuss how these differences lead to developmental plasticity in offspring phenotype. We finish by reviewing the ecological and conservation consequences of nutritional-driven developmental plasticity in reptiles. If nutritional-driven developmental plasticity has fitness consequences, then understanding the basis of this plasticity has exciting potential to identify how reptile recruitment is affected by environmental changes in food supply. Such knowledge is critical to our ability to protect taxa threatened by environmental change.

Geographical Area and Life History Traits Influence Diet in an Arctic Marine Predator

Global changes are thought to affect most Arctic species, yet some populations are more at risk. Today, the Barents Sea ecoregion is suffering the strongest sea ice retreat ever measured; and these changes are suspected to modify food access and thus diet of several species. Biochemical diet tracers enable investigation of diet in species such as polar bears (Ursus maritimus). We examined individual diet variation of female polar bears in Svalbard, Norway, and related it to year, season (spring and autumn), sampling area and breeding status (solitary, with cubs of the year or yearlings). Sampling areas were split according to their ice cover: North-West (less sea ice cover), South-East (larger amplitude in sea ice extent) and North-East/South-West (NESW) as bears from that zone are more mobile among all regions of Svalbard. We measured fatty acid (FA) composition in adipose tissue and carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes in plasma and red blood cells. Females feeding in the North-West area had lower δ¹⁵N values than those from the NESW. In South-East females, δ¹³C values were lower in autumn compared to spring and females seemed less selective in their diet as depicted by large variances in stable isotope values. Considering the differences in FA composition and stable isotope values, we suggest that females from the North-West and South-East could ingest a higher proportion of avian prey. With regard to breeding status, solitary females had higher δ¹⁵N values and smaller variance in their stable isotopic values than females with cubs, suggesting that solitary females were more selective and prey on higher trophic level species (i.e. seals). Overall, our results indicate that prey availability for Svalbard polar bears varies according to geographical area and prey selectivity differs according to breeding status. Our findings suggest that complex changes in sea ice and prey availability will interact to affect Svalbard polar bear feeding patterns and associated nutrition.

Influence of in ovo mercury exposure, lake acidity, and other factors on common loon egg and chick quality in Wisconsin

A field study was conducted in Wisconsin (USA) to characterize in ovo mercury (Hg) exposure in common loons (Gavia immer). Total Hg mass fractions ranged from 0.17 µg/g to 1.23 µg/g wet weight in eggs collected from nests on lakes representing a wide range of pH (5.0-8.1) and were modeled as a function of maternal loon Hg exposure and egg laying order. Blood total Hg mass fractions in a sample of loon chicks ranged from 0.84 µg/g to 3.86 µg/g wet weight at hatch. Factors other than mercury exposure that may have persistent consequences on development of chicks from eggs collected on low-pH lakes (i.e., egg selenium, calcium, and fatty acid mass fractions) do not seem to be contributing to reported differences in loon chick quality as a function of lake pH. However, it was observed that adult male loons holding territories on neutral-pH lakes were larger on average than those occupying territories on low-pH lakes. Differences in adult body size of common loons holding territories on neutral-versus low-pH lakes may have genetic implications for differences in lake-source-related quality (i.e., size) in chicks. The tendency for high in ovo Hg exposure and smaller adult male size to co-occur in low-pH lakes complicates the interpretation of the relative contributions of each to resulting chick quality.

Egg yolk fatty acids as a proxy to quantify diets of female Spectacled Eiders (Somateria fischeri)

Determining the diets of threatened Spectacled Eiders (Somateria fischeri (Brandt, 1847)) in relation to life-history stages will provide information to help identify and characterize their critical habitats. Quantitative fatty acid signature analysis (QFASA) is a novel tool that estimates the proportion of diet items in consumers from their fat depots. We conducted feeding experiments to validate the use of QFASA to estimate the mixed diets of captive female Spectacled Eiders using egg yolk fatty acids (FA) collected in 2008 and 2009. Calibration coefficients (CCs) for individual FA were developed to account for FA modification (due to eider lipid metabolism) from diets of eiders into egg yolk. We also compared the FA profiles between fertile and infertile eggs. Egg yolk FA profiles did not differ significantly between infertile and fertile eggs collected in either year. Using the CCs developed from eggs collected in 2008, QFASA closely estimated the 2009 diet composition of eiders. We conclude that using infertile eggs has the potential to provide a noninvasive method to elucidate diets of breeding female Spectacled Eiders and possibly other avian species, and to provide insight into understanding the sources (i.e., marine wintering or freshwater breeding habitat) and timing (i.e., prebreeding or breeding) of nutrient acquisition during reproduction.

Between-population differences in egg composition in Blue Tits (Cyanistes caeruleus)

Egg production may be influenced by environmental conditions such as local climate or food availability, which may impose physiological constraints on the acquisition and mobilization of egg constituents. We analyzed egg composition of free-ranging female Blue Tits ( Cyanistes caeruleus (L., 1758)) in both deciduous and evergreen oak habitats, which showed large differences in temperature and food availability. We found marked interhabitat differences in yolk mass, shell mass, protein content, and the abundance of linolenic (18:3) and palmitoleic (16:1) fatty acids. A weak but significant decline in total lipid content, as well as 14:0, 16:0, and 18:0 fatty acids, through the laying sequence was also detected. To our knowledge, this is the first evidence of between-population differences in nutrient allocation in eggs for a wild passerine. These differences in egg composition could be viewed as evidence of habitat-specific physiological and nutritional constraints, which in turn may contribute to the contrasting differences in timing of breeding and clutch size that we observed between both habitats. Our results point out the importance of habitat differences in our understanding of the causes and consequences of interhabitat phenotypic variation in breeding traits (timing of egg laying, clutch size) and variation in nestling traits such as growth and development.

Timing of incorporation of docosahexaenoic acid into brain and muscle phospholipids during precocial and altricial modes of avian development

We investigated the possibilities that the proportion of docosahexaenoic acid (DHA) in phospholipids of brain and skeletal muscle at hatch, and the ontogenetic timing of the DHA accretion spurt in these tissues, might serve as indices of neonatal functional maturity that discriminate between precocial and altricial avian developmental modes. Comparison of the fatty acid profiles of the initial and residual yolks of two free-living altricial species, the swallow (Hirundo rustica) and the sparrow (Passer domesticus), reveals that, in contrast to precocial birds, there is no preferential uptake of DHA from the yolk during embryonic development. At hatch, the proportions of DHA in brain phospholipid (wt.% of fatty acids) of the swallow and sparrow, at 8.1% and 5.0%, respectively, are far lower than the values (16.9-19.6%) reported for non-altricial species. This reflects a marked difference in the timing of the brain DHA accretion spurt, which occurs during the first half of the embryonic period of precocial birds, but is largely delayed until after hatching in the altricial species. By the time of fledging, the proportion of DHA in the swallow brain phospholipid has increased to 14.3%. For non-altricial birds, the brain DHA concentration at hatch shows little interspecies variation, despite major differences in yolk DHA content. The proportions of DHA in leg muscle phospholipid of the newly hatched swallow and sparrow, at 2.9% and 2.5%, respectively, are far lower than the value (6.7%) for the precocial chicken. Again, this relates to differences in developmental timing, with muscle DHA accretion occurring in the first half of the chicken's embryonic period, whereas, in the swallow, this increase is delayed until after hatching. By the time of fledging in the swallow, DHA forms 9.3% of muscle phospholipid fatty acids, equivalent to the level attained in chicken muscle at the mid-embryo stage. The results indicate a clear distinction between altricial and non-altricial avian species in the timing of tissue DHA accretion during development, presumably reflecting differences in neonatal functional maturity.

Biosynthesis of oleic, arachidonic and docosahexaenoic acids from their C18 precursors in the yolk sac membrane of the avian embryo

The yolk sac membrane (YSM) of the chicken embryo is known to express delta-9 and delta-6 desaturase activities, suggesting that biosynthesis of the unsaturated fatty acids 18:1n-9, 20:4n-6 and 22:6n-3 might occur during the transfer of yolk lipids across the YSM. If so, this biosynthesis could help to satisfy the demands of the embryonic tissues for these unsaturates. To assess the ability of the YSM to perform these conversions, pieces of the tissue were incubated in vitro with the precursor fatty acids, 14C-18:0, 14C-18:2n-6 or 14C-18:3n-3, and the recovery of radioactivity in the respective products, 18:1n-9, 20:4n-6 and 22:6n-3, was determined. After 4 h of continuous incubation, radioactivity from these precursors was incorporated primarily into triacylglycerol and phospholipid of the tissue pieces. Only small proportions (0.3-4.7%) of this incorporated radioactivity were, however, recovered as 18:1n-9, 20:4n-6 or 22:6n-3. The majority of the incorporated label was retained in the form of the precursor fatty acids. After a 1-h pulse incubation with the 14C precursors, followed by a 3-h chase incubation in the absence of exogenous label, the conversion of incorporated radioactivity to the end product unsaturates was again relatively low (0.5-8.1%). Thus, although conversions of the precursors to the end product fatty acids were detectable in this system, the biosynthesis of these unsaturates is apparently a quantitatively minor pathway in the YSM. Nevertheless, since the amount of 18:2n-6 in the yolk lipids far exceeds that of 20:4n-6, the conversion of even a small proportion of the former to the latter fatty acid could significantly increase the supply of 20:4n-6 to the embryonic tissues.

Thyroid rhythm phenotypes and hominid evolution: a new paradigm implicates pulsatile hormone secretion in speciation and adaptation changes

Thyroid hormones (THs, T(3)/T(4)) are essential central regulators that link many biological tasks, including embryonic and post-natal growth, reproductive function, and the behavioral and physiological responses to stress. Recently I proposed a novel theory to explain the role of THs in vertebrate evolution. Here I review the concept and discuss its ability to explain changes over time in hominid morphology, behavior and life history. THs are produced in a distinctly pulsatile manner and appear to generate species-specific TH rhythms with distinct ontogenic shifts. Individual variations in genetically controlled TH rhythms (TR phenotypes) must generate coordinated individual variation in morphology, reproduction and behavior within populations. Selection for any manifestation of a particular TR phenotype in an ancestral population selects all traits under thyroid control, resulting in rapid and well-coordinated changes in descendants. The concept provides the first really plausible explanation for a number of phenomena, including the convergent evolution of bipedalism in early hominids, species-specific sexual dimorphism, coordinated changes in morphology, brain function and gut length over time in hominids, cold adaptation in Homo neanderthalensis, the possible independent evolution of H. sapiens in Asia, and regional adaptation of hominid populations. This new paradigm provides a unique theoretical framework for explaining human origins that has important implications for human health.