Disentangling the "many-eyes", "dilution effect", "selfish herd", and "distracted prey" hypotheses in shaping alert and flight initiation distance in a colonial seabird.

Group living is thought to have important antipredator benefits for animals, owing to the mechanisms of shared vigilance ("many-eyes" hypothesis), risk dilution ("dilution effect" hypothesis), and relative safety in the center of the group ("selfish herd" hypothesis). However, it can also incur costs since social stimuli, such as conspecific aggression, may distract individuals from anti-predator behavior ("distracted prey" hypothesis). We simultaneously evaluated how these four different hypotheses shape anti-predator behaviors of breeding king penguins (Aptenodytes patagonicus), which aggregate into large colonies, experience frequent aggressive social interactions, and are regularly exposed to predation by giant petrels (Macronectes sp.) and brown skuas (Catharacta loonbergi) when breeding on land. We approached 200 incubating penguins at four different periods of the breeding season across a range of overall increasing colony densities. We measured the distance at which focal birds detected the approaching threat (alert distance: AD), whether birds decided to flee or not, and the distance of flight initiation (flight initiation distance: FID, viz. the bird attempting to walk away with its egg on its feet). We quantified relative local neighbor density, centrality within the colony (rank), and the number of aggressions the focal bird emitted towards neighbors during the approach. We found that birds engaged in aggressive conflicts with neighbors were less likely to flee, and that increasing relative local neighbor density at low and medium overall colony density resulted in a decrease in bird AD, both supporting the "distracted prey" hypothesis. However, at maximal overall colony density, increasing relative local neighbor density resulted in longer AD, supporting the "many-eyes" hypothesis. We found no support for the "dilution effect" and "selfish herd" hypotheses, and no effects of any hypothesis on FID.

An integrative appraisal of the hormonal and metabolic changes induced by acute stress using king penguins as a model.

A large number of studies have focused on the reactivity of the hypothalamic-pituitaryadrenal (HPA) axis and the consequences of glucocorticoids (GC) in mediating life-history trade-offs. Although short-term increases in GCs are viewed as adaptive, mobilizing energy substrates allowing animals to deal with impending threats (e.g. stimulating hepatic gluconeogenesis, stimulating lipolysis, mobilizing amino acids), few studies have actually measured the exact time-course of substrate mobilisation in response to acute stress in natural conditions. We evaluated the hormonal and metabolic components of the stress response to acute stress in 32 free-living king penguins (Aptenodytes patagonicus). We monitored changes in blood GCs (corticosterone, CORT), glucose, lactate, ketone bodies (ß-hydroxybutyrate), non-esterified fatty acids, and uric acid in response to a standardized capture-restraint protocol lasting for up to 90min. Furthermore, we tested whether the vigilance status of the animal (alert or asleep) affected its perception of the capture, thereby modulating the hormonal and metabolic stress responses. The time course of energy mobilisation followed the characteristic pattern expected from laboratory and theoretical models, with a rapid depletion of those energy stores linked to rapid adrenergic responses (i.e. glucose and ketone bodies), followed by a mobilisation of energy stores associated with the sustained longer-term GC response (i.e. fats and protein stores). HPA reactivity was generally slower than reported in other birds, and there was high inter-individual variability. Sleeping birds had higher GC and glucose responses to acute stress, suggesting a more rapid mobilization of energy stores. Our results highlight the importance of considering HPA and metabolic responses to acute stress against species-specific life history and ecological relevant backgrounds.

Breeding status affects the hormonal and metabolic response to acute stress in a long-lived seabird, the king penguin.

Stress responses are suggested to physiologically underlie parental decisions promoting the redirection of behaviour away from offspring care when survival is jeopardized (e.g., when facing a predator). Besides this classical view, the "brood-value hypothesis" suggests that parents' stress responses may be adaptively attenuated to increase fitness, ensuring continued breeding when the relative value of the brood is high. Here, we test the brood-value hypothesis in breeding king penguins (Aptenodytes patagonicus), long-lived seabirds for which the energy commitment to reproduction is high. We subjected birds at different breeding stages (courtship, incubation and chick brooding) to an acute 30-min capture stress and measured their hormonal (corticosterone, CORT) and metabolic (non-esterified fatty acid, NEFA) responses to stress. We found that CORT responses were markedly attenuated in chick-brooding birds when compared to earlier stages of breeding (courtship and incubation). In addition, NEFA responses appeared to be rapidly attenuated in incubating and brooding birds, but a progressive increase in NEFA plasma levels in courting birds suggested energy mobilization to deal with the threat. Our results support the idea that stress responses may constitute an important life-history mechanism mediating parental reproductive decisions in relation to their expected fitness outcome.

Modulation of heart rate response to acute stressors throughout the breeding season in the king penguin Aptenodytes patagonicus.

'Fight-or-flight' stress responses allow animals to cope adaptively to sudden threats by mobilizing energy resources and priming the body for action. Because such responses can be costly and redirect behavior and energy from reproduction to survival, they are likely to be shaped by specific life-history stages, depending on the available energy resources and the commitment to reproduction. Here, we consider how heart rate (HR) responses to acute stressors are affected by the advancing breeding season in a colonial seabird, the king penguin (Aptenodytes patagonicus). We subjected 77 birds (44 males, 33 females) at various stages of incubation and chick-rearing to three experimental stressors (metal sound, distant approach and capture) known to vary both in their intensity and associated risk, and monitored their HR responses. Our results show that HR increase in response to acute stressors was progressively attenuated with the stage of breeding from incubation to chick-rearing. Stress responses did not vary according to nutritional status or seasonal timing (whether breeding was initiated early or late in the season), but were markedly lower during chick-rearing than during incubation. This pattern was obvious for all three stressors. We discuss how 'fight-or-flight' responses may be modulated by considering the energy commitment to breeding, nutritional status and reproductive value of the brood in breeding seabirds.

Rovers minimize human disturbance in research on wild animals.

Investigating wild animals while minimizing human disturbance remains an important methodological challenge. When approached by a remote-operated vehicle (rover) which can be equipped to make radio-frequency identifications, wild penguins had significantly lower and shorter stress responses (determined by heart rate and behavior) than when approached by humans. Upon immobilization, the rover-unlike humans-did not disorganize colony structure, and stress rapidly ceased. Thus, rovers can reduce human disturbance of wild animals and the resulting scientific bias.

Stress hormones in relation to breeding status and territory location in colonial king penguin: a role for social density?

Because glucocorticoid (stress) hormones fundamentally affect various aspects of the behaviour, life history and fitness of free-living vertebrates, there is a need to understand the environmental factors shaping their variation in natural populations. Here, we examined whether spatial heterogeneity in breeding territory quality affected the stress of colonial king penguin (Aptenodytes patagonicus). We assessed the effects of local climate (wind, sun and ambient temperature) and social conditions (number of neighbours, distance to neighbours) on the baseline levels of plasma total corticosterone (CORT) in 77 incubating and 42 chick-brooding birds, breeding on territories of central or peripheral colony location. We also assessed the oxidative stress status of a sub-sample of central vs. peripheral chick-brooders to determine whether chronic stress arose from breeding on specific territories. On average, we found that brooders had 55% higher CORT levels than incubators. Regardless of breeding status, central birds experienced greater social density (higher number of neighbours, shorter distance between territories) and had higher CORT levels than peripheral birds. Increasing social density positively explained 40% of the variation in CORT levels of both incubators and brooders, but the effect was more pronounced in brooders. In contrast, climate was similar among breeding territories and did not significantly affect the CORT levels of breeding birds. In brooders, oxidative stress status was not affected by local density or weather conditions. These results highlight that local heterogeneity in breeding (including social) conditions may strongly affect the stress levels of breeding seabirds. The fitness consequences of such variation remain to be investigated.

Interspecific variations in the gastrointestinal microbiota in penguins.

Despite the enormous amount of data available on the importance of the gastrointestinal (GI) microbiota in vertebrate (especially mammals), information on the GI microbiota of seabirds remains incomplete. As with many seabirds, penguins have a unique digestive physiology that enables them to store large reserves of adipose tissue, protein, and lipids. This study used quantitative real-time polymerase chain reaction (qPCR) and 16S rRNA gene pyrosequencing to characterize the interspecific variations of the GI microbiota of four penguin species: the king, gentoo, macaroni, and little penguin. The qPCR results indicated that there were significant differences in the abundance of the major phyla Firmicutes, Bacteroides, Actinobacteria, and Proteobacteria. A total of 132,340, 18,336, 6324, and 4826 near full-length 16S rRNA gene sequences were amplified from fecal samples collected from king, gentoo, macaroni, and little penguins, respectively. A total of 13 phyla were identified with Firmicutes, Bacteroidetes, Proteobacteria, and Fusobacteria dominating the composition; however, there were major differences in the relative abundance of the phyla. In addition, this study documented the presence of known human pathogens, such as Campylobacter, Helicobacter, Prevotella, Veillonella, Erysipelotrichaceae, Neisseria, and Mycoplasma. However, their role in disease in penguins remains unknown. To our knowledge, this is the first study to provide an in-depth investigation of the GI microbiota of penguins.

Body girth as an alternative to body mass for establishing condition indexes in field studies: a validation in the king penguin.

Body mass and body condition are often tightly linked to animal health and fitness in the wild and thus are key measures for ecophysiologists and behavioral ecologists. In some animals, such as large seabird species, obtaining indexes of structural size is relatively easy, whereas measuring body mass under specific field circumstances may be more of a challenge. Here, we suggest an alternative, easily measurable, and reliable surrogate of body mass in field studies, that is, body girth. Using 234 free-living king penguins (Aptenodytes patagonicus) at various stages of molt and breeding, we measured body girth under the flippers, body mass, and bill and flipper length. We found that body girth was strongly and positively related to body mass in both molting (R(2) = 0.91) and breeding (R(2) = 0.73) birds, with the mean error around our predictions being 6.4%. Body girth appeared to be a reliable proxy measure of body mass because the relationship did not vary according to year and experimenter, bird sex, or stage within breeding groups. Body girth was, however, a weak proxy of body mass in birds at the end of molt, probably because most of those birds had reached a critical depletion of energy stores. Body condition indexes established from ordinary least squares regressions of either body girth or body mass on structural size were highly correlated (r(s) = 0.91), suggesting that body girth was as good as body mass in establishing body condition indexes in king penguins. Body girth may prove a useful proxy to body mass for estimating body condition in field investigations and could likely provide similar information in other penguins and large animals that may be complicated to weigh in the wild.

Coping with continuous human disturbance in the wild: insights from penguin heart rate response to various stressors.

BACKGROUND: A central question for ecologists is the extent to which anthropogenic disturbances (e.g. tourism) might impact wildlife and affect the systems under study. From a research perspective, identifying the effects of human disturbance caused by research-related activities is crucial in order to understand and account for potential biases and derive appropriate conclusions from the data. RESULTS: Here, we document a case of biological adjustment to chronic human disturbance in a colonial seabird, the king penguin (Aptenodytes patagonicus), breeding on remote and protected islands of the Southern ocean. Using heart rate (HR) as a measure of the stress response, we show that, in a colony with areas exposed to the continuous presence of humans (including scientists) for over 50 years, penguins have adjusted to human disturbance and habituated to certain, but not all, types of stressors. When compared to birds breeding in relatively undisturbed areas, birds in areas of high chronic human disturbance were found to exhibit attenuated HR responses to acute anthropogenic stressors of low-intensity (i.e. sounds or human approaches) to which they had been subjected intensely over the years. However, such attenuation was not apparent for high-intensity stressors (i.e. captures for scientific research) which only a few individuals experience each year. CONCLUSIONS: Habituation to anthropogenic sounds/approaches could be an adaptation to deal with chronic innocuous stressors, and beneficial from a research perspective. Alternately, whether penguins have actually habituated to anthropogenic disturbances over time or whether human presence has driven the directional selection of human-tolerant phenotypes, remains an open question with profound ecological and conservation implications, and emphasizes the need for more knowledge on the effects of human disturbance on long-term studied populations.

Hormonal responses to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups.

Surviving prolonged fasting implies closely regulated alterations in fuel provisioning to meet metabolic requirements, while preserving homeostasis. Little is known, however, of the endocrine regulations governing such metabolic adaptations in naturally fasting free-ranging animals. The hormonal responses to natural prolonged fasting and how they correlate to the metabolic adaptations observed, were investigated in subantarctic fur seal (Arctocephalus tropicalis) pups, which, because of the intermittent pattern of maternal attendance, repeatedly endure exceptionally long fasting episodes throughout their development (1-3 mo). Phase I fasting was characterized by a dramatic decrease in plasma insulin, glucagon, leptin, and total l-thyroxine (T(4)) associated with reductions in mass-specific resting metabolic rate (RMR), plasma triglycerides, glycerol, and urea-to-creatine ratio, while nonesterified fatty acids (NEFA) and ß-OHB increased. In contrast, the metabolic steady-state of phase II fasting reached within 6 days was associated with minimal concentrations of insulin, glucagon, and leptin; unchanged cortisol and triiodothyronine (T(3)); and moderately increased T(4). The early fall in insulin and leptin may mediate the shift to the strategy of energy conservation, protein sparing, and primary reliance on body lipids observed in response to the cessation of feeding. In contrast to the typical mammalian starvation response, nonelevated cortisol and minimal glucagon levels may contribute to body protein preservation and downregulation of catabolic pathways, in general. Furthermore, thyroid hormones may be involved in a process of energy conservation, independent of pups' nutritional state. These original hormonal settings might reflect an adaptation to the otariid repeated fasting pattern and emphasize the crucial importance of a tight physiological control over metabolism to survive extreme energetic constraints.

It costs to be clean and fit: energetics of comfort behavior in breeding-fasting penguins.

BACKGROUND: Birds may allocate a significant part of time to comfort behavior (e.g., preening, stretching, shaking, etc.) in order to eliminate parasites, maintain plumage integrity, and possibly reduce muscular ankylosis. Understanding the adaptive value of comfort behavior would benefit from knowledge on the energy costs animals are willing to pay to maintain it, particularly under situations of energy constraints, e.g., during fasting. We determined time and energy devoted to comfort activities in freely breeding king penguins (Aptenodytes patagonicus), seabirds known to fast for up to one month during incubation shifts ashore. METHODOLOGY/PRINCIPAL FINDINGS: A time budget was estimated from focal and scan sampling field observations and the energy cost of comfort activities was calculated from the associated increase in heart rate (HR) during comfort episodes, using previously determined equations relating HR to energy expenditure. We show that incubating birds spent 22% of their daily time budget in comfort behavior (with no differences between day and night) mainly devoted to preening (73%) and head/body shaking (16%). During comfort behavior, energy expenditure averaged 1.24 times resting metabolic rate (RMR) and the corresponding energy cost (i.e., energy expended in excess to RMR) was 58 kJ/hr. Energy expenditure varied greatly among various types of comfort behavior, ranging from 1.03 (yawning) to 1.78 (stretching) times RMR. Comfort behavior contributed 8.8-9.3% to total daily energy expenditure and 69.4-73.5% to energy expended daily for activity. About half of this energy was expended caring for plumage. CONCLUSION/SIGNIFICANCE: This study is the first to estimate the contribution of comfort behavior to overall energy budget in a free-living animal. It shows that although breeding on a tight energy budget, king penguins devote a substantial amount of time and energy to comfort behavior. Such findings underline the importance of comfort behavior for the fitness of colonial seabirds.

Heterothermy in growing king penguins.

A drop in body temperature allows significant energy savings in endotherms, but facultative heterothermy is usually restricted to small animals. Here we report that king penguin chicks (Aptenodytes patagonicus), which are able to fast for up to 5 months in winter, undergo marked seasonal heterothermy during this period of general food scarcity and slow-down of growth. They also experience short-term heterothermy below 20 °C in the lower abdomen during the intense (re)feeding period in spring, induced by cold meals and adverse weather. The heterothermic response involves reductions in peripheral temperature, reductions in thermal core volume and temporal abandonment of high core temperature. Among climate variables, air temperature and wind speed show the strongest effect on body temperature, but their effect size depends on physiological state. The observed heterothermy is remarkable for such a large bird (10 kg before fasting), which may account for its unrivalled fasting capacity among birds.

Differential muscular myosin heavy chain expression of the pectoral and pelvic girdles during early growth in the king penguin (Aptenodytes patagonicus) chick.

Continuous growth, associated with a steady parental food supply, is a general pattern in offspring development. So that young chicks can acquire their locomotor independence, this period is usually marked by a fast maturation of muscles, during which different myosin heavy chain (MyHC) isoforms are expressed. However, parental food provisioning may fluctuate seasonally, and offspring therefore face a challenge to ensure the necessary maturation of their tissues when energy is limited. To address this trade-off we investigated muscle maturation in both the pectoral and pelvic girdles of king penguin chicks. This species has an exceptionally long rearing period (1 year), which is prolonged when parental food provisioning is drastically reduced during the sub-Antarctic winter. Approximately 1 month post hatching, chicks acquire a functional pedestrian locomotion, which uses pelvic muscles, whereas swimming, which uses the pectoral muscles, only occurs 1 year later. We therefore tested the hypothesis that the MyHC content of the leg muscles reaches a mature state before those of the pectoral muscles. We found that leg muscle MyHC composition changed with the progressive acquisition of pedestrian locomotion, whereas pectoral muscle fibres reached their mature MyHC profile as early as hatching. Contrary to our predictions, the acquisition of the adult profile in pectoral muscles could be related to an early maturation of the contractile muscular proteins, presumably associated with early thermoregulatory capacities of chicks, necessary for survival in their cold environment. This differential maturation appears to reconcile both the locomotor and environmental constraints of king penguin chicks during growth.

Physiological response to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups: metabolic rates, energy reserve utilization, and water fluxes.

Surviving prolonged fasting requires various metabolic adaptations, such as energy and protein sparing, notably when animals are simultaneously engaged in energy-demanding processes such as growth. Due to the intermittent pattern of maternal attendance, subantarctic fur seal pups have to repeatedly endure exceptionally long fasting episodes throughout the 10-mo rearing period while preparing for nutritional independence. Their metabolic responses to natural prolonged fasting (33.4 +/- 3.3 days) were investigated at 7 mo of age. Within 4-6 fasting days, pups shifted into a stage of metabolic economy characterized by a minimal rate of body mass loss (0.7%/day) and decreased resting metabolic rate (5.9 +/- 0.1 ml O(2)xkg(-1)xday(-1)) that was only 10% above the level predicted for adult terrestrial mammals. Field metabolic rate (289 +/- 10 kJxkg(-1)xday(-1)) and water influx (7.9 +/- 0.9 mlxkg(-1)xday(-1)) were also among the lowest reported for any young otariid, suggesting minimized energy allocation to behavioral activity and thermoregulation. Furthermore, lean tissue degradation was dramatically reduced. High initial adiposity (>48%) and predominant reliance on lipid catabolism likely contributed to the exceptional degree of protein sparing attained. Blood chemistry supported these findings and suggested utilization of alternative fuels, such as beta-hydroxybutyrate and de novo synthesized glucose from fat-released glycerol. Regardless of sex and body condition, pups tended to adopt a convergent strategy of extreme energy and lean body mass conservation that appears highly adaptive for it allows some tissue growth during the repeated episodes of prolonged fasting they experience throughout their development.

Restoration of body energy reserves during refeeding in rats is dependent on both the intensity of energy restriction and the metabolic status at the onset of refeeding [corrected].

During starvation, after a short dynamic period of adaptation (phase I), a metabolic steady state is reached in which proteins are spared and lipids provide most of the energy expended [phase II (P2)]. However, protein breakdown increases dramatically once a lower threshold of body lipids is reached [phase III (P3)]. Body composition, energy intake, energy expenditure, and energy efficiency were determined in 8 groups of rats (fed, food-deprived up to P2 or P3 of starvation and refed for 3 d, 7 d, or until body mass restoration) to determine whether the kinetics of lipid and/or protein reserve recovery may be slowed down when refeeding occurs after the lipid threshold has been reached. Despite larger losses, P3 refed rats restored their body reserves as efficiently as those refed in P2. Whatever the nutritional status at the onset of refeeding, rehydration occurred first and hyperphagia played a more important role than hypometabolism in the restoration of the lost reserves. However, the pattern of body component gains was different during early refeeding. In P3 refed rats, body lipids were restored preferentially by significant contribution from endogenous lipid production. Thus, the extent of lipid depletion has important consequences for the restoration pattern of the body reserves. It depends not only on the intensity of the energy restriction (partial or total) as already demonstrated but also on the metabolic status at the onset of refeeding. These results may have significant implications on the way refeeding should be conducted after severe energy depletion.

A role for corticosterone and food restriction in the fledging of nestling White storks.

Fledging is a critical period in the life of a bird, notably because at this stage under-development and lack of experience in searching for food may impair survival. The behavioral changes that accompany nest departure are therefore expected to be finely tuned to body condition and growth by endocrine processes. This study examines the possible involvement of corticosterone (CORT) in the stimulation of fledging in White storks through measurement of the changes in its plasma levels in relation to growth, nutritional status and the hatching rank of nestlings. For the first time in nest-bound chicks, we show that fledging is preceded by a marked and progressive 4 fold increase in baseline plasma CORT levels concomitant with an increase in locomotor activity (wing flapping) at the nest. Data on changes in body size, body mass, plasma metabolites and feeding frequency support the view that the increase in plasma CORT was induced by food restriction rather than being endogenously programmed. The timing and intensity of plasma CORT increase was dependent on the hatching rank within a brood, this increase being blunted in the less developed chicks possibly to avoid the impairment of final wing growth. These results show that an increase in plasma CORT as a result of food restriction and through the stimulation of locomotor activity is involved in the control of fledging in White storks. Moreover the CORT increase is adjusted to the hatching rank-related growth status of nestlings.

Is fledging in king penguin chicks related to changes in metabolic or endocrinal status?

This study examines the possibility that metabolic or endocrinal factors initiate fledging in the king penguin, a semi-altricial seabird species breeding a single chick on the ground. Chick fledging (departure to sea) occurred 5d after completion of the molt. It was preceded by a 16d fasting period and by a 7-fold increase in locomotor activity. From the measurement of the plasma concentration of metabolites and of glucagon and insulin, pre-fledging king penguin chicks were found to adapt to fasting in a classical way, i.e. by sparing body protein and mobilizing fat stores. At fledging, chicks were in phase II of fasting and their departure to sea was not stimulated by reaching critical energy depletion (phase III), in contrast to that which has been reported in breeding-fasting adults. The plasma level of corticosterone remained unchanged throughout the whole pre-fledging period, providing no support for a role of this stress-hormone in the facilitation of fledging. Thus, king penguin fledglings did not appear to be environmentally or nutritionally stressed. The plasma levels of thyroid hormones were elevated during the pre-fledging molt, in accordance with their key role in molt control in adult penguins. These levels declined by the time of the molt end, the plasma level of T4 thereafter being directly related to the time left before fledging. These results do not support the view that chronically elevated levels of thyroid hormones are required for the energy-demanding transition between being ashore and in cold water, but they suggest that the maintenance of high T4 levels may delay fledging.

Spontaneous egg or chick abandonment in energy-depleted king penguins: a role for corticosterone and prolactin?

Various exogenous or endogenous factors may induce an emergency response in birds, redirecting current activity towards survival. In fasting, breeding penguins, the achievement of a critical energy depletion was suggested to induce egg abandonment and departure to sea for re-feeding. How such a behavioral shift is hormonally controlled remains unknown. The possible involvement of corticosterone and prolactin was examined by characterizing the nutritional and hormonal states of king penguins at egg abandonment. Further, we tested if these states differ according to whether an egg or a chick is abandoned, and according to the timing of breeding. In every case of abandonment, birds were in phase III fasting characterized by accelerated protein catabolism. However, body condition at egg abandonment was lower in early than in late breeders, suggesting that king penguins are willing to tolerate a larger energy depletion when their potential breeding success is high. At egg and chick abandonment, plasma corticosterone levels were, respectively, increased by 2- and 4-fold, whereas plasma prolactin levels were, respectively, depressed by 3- and 1.4-fold. The increase in plasma corticosterone and the decrease in plasma prolactin could be involved in the control of abandonment by, respectively, stimulating the drive to re-feed and diminishing the drive to incubate or brood. The smaller decrease in prolactin levels and the greater increase in corticosterone levels observed at chick vs egg abandonment suggest that, in addition to nutritionally-related stimuli, tactile or audible stimuli from the egg or chick could intervene in the endocrine control of abandonment.

Metabolic fate of yolk fatty acids in the developing king penguin embryo.

This study examines the metabolic fate of total and individual yolk fatty acids (FA) during the embryonic development of the king penguin, a seabird characterized by prolonged incubation (53 days) and hatching (3 days) periods, and a high n-3/n-6 polyunsaturated FA ratio in the egg. Of the approximately 15 g of total FA initially present in the egg lipid, 87% was transferred to the embryo by the time of hatching, the remaining 13% being present in the internalized yolk sac of the chick. During the whole incubation, 83% of the transferred FA was oxidized for energy, with only 17% incorporated into embryo lipids. Prehatching (days 0-49), the fat stores (triacylglycerol) accounted for 58% of the total FA incorporated into embryo lipid. During hatching (days 49-53), 40% of the FA of the fat stores was mobilized, the mobilization of individual FA being nonselective. At hatch, 53% of the arachidonic acid (20:4n-6) of the initial yolk had been incorporated into embryo lipid compared with only 15% of the total FA and 17-24% of the various n-3 polyunsaturated FA. Similarly, only 32% of the yolk's initial content of 20:4n-6 was oxidized for energy during development compared with 72% of the total FA and 58-66% of the n-3 polyunsaturated FA. The high partitioning of yolk FA toward oxidization and the intense mobilization of fat store FA during hatching most likely reflect the high energy cost of the long incubation and hatching periods of the king penguin. The preferential partitioning of 20:4n-6 into the structural lipid of the embryo in the face of its low content in the yolk may reflect the important roles of this FA in tissue function.

Establishment of the fatty acid profile of the brain of the king penguin (Aptenodytes patagonicus) at hatch: effects of a yolk that is naturally rich in n-3 polyunsaturates.

Because the yolk lipids of the king penguin (Aptenodytes patagonicus) contain the highest concentrations of long-chain n-3 polyunsaturated fatty acids yet reported for an avian species, the consequences for the establishment of the brain's fatty acid profile in the embryo were investigated. To place the results in context, the fatty acid compositions of yolk lipid and brain phospholipid of the king penguin were compared with those from three other species of free-living birds. The proportions of docosahexaenoic acid (22:6n-3; DHA) in the total lipid of the initial yolks for the Canada goose (Branta canadensis), mallard (Anas platyrhynchos), moorhen (Gallinula chloropus), and king penguin were (% w/w of fatty acids) 1.0+/-0.1, 1.9+/-0.2, 3.3+/-0.1, and 5.9+/-0.2, respectively. The respective concentrations of DHA (% w/w of phospholipid fatty acids) in brains of the newly hatched chicks of these same species were 18.5+/-0.2, 19.6+/-0.7, 16.9+/-0.4, and 17.6+/-0.1. Thus, the natural interspecies diversity in yolk fatty acid profiles does not necessarily produce major differences in the DHA content of the developing brain. Only about 1% of the amount of DHA initially present in the yolk was recovered in the brain of the penguin at hatch. There was no preferential uptake of DHA from the yolk during development of the king penguin.