Acquisition of gliding skills by Weddell seal (Leptonychotes weddellii) pups during lactation

Pinnipeds give birth to their pups ashore or on ice and forage in water. Therefore, neonates initially lack the adaptations to sustain prolonged underwater diving activity. Although the physiological development for breath-holding during diving has been investigated in seal pups, little is known about the concurrent development of behavioral adaptations during lactation. In this study, multisensor data loggers were used to record diving behavior and swimming gaits of pre-weaned Weddell seal (Leptonychotes weddellii) pups. Experiments were conducted in 16 pups at the Syowa Station, Antarctica, from November to December 1999 and 2004. Swimming speeds, dive depths and flipper stroking rates were recorded for each individual for about 24 h. We found that the glide index during ascending was increased with body length, whereas the dominant stroke cycle frequency were not affected by body length, dive depth and descent or ascent phase. All pups had significantly higher stroke rates in descent than in ascent, but there was no difference between swimming speed. As we found a positive relationship between the body length and age, we considered body length as an index of growth. Therefore, we conclude that pups gradually acquire the ability to glide with utilizing positive buoyancy during ascending toward the end of lactation.     

Renal responses to plasma volume expansion and hyperosmolality in fasting seal pups

Renal responses were quantified in northern elephant seal (Mirounga angustirostris) pups during their postweaning fast to examine their excretory capabilities. Pups were infused with either isotonic (0.9%; n = 8; Iso) or hypertonic (16.7%; n = 7; Hyper) saline via an indwelling catheter such that each pup received 3 mmol NaCl/kg. Diuresis after the infusions was similar in magnitude between the two treatments. Osmotic clearance increased by 37% in Iso and 252% in Hyper. Free water clearance was reduced 3.4-fold in Hyper but was not significantly altered in Iso. Glomerular filtration rate increased 71% in the 24-h period after Hyper, but no net change occurred during the same time after Iso. Natriuresis increased 3.6-fold in Iso and 5.3-fold in Hyper. Iso decreased plasma arginine vasopressin (AVP) and cortisol acutely, whereas Hyper increased plasma and excreted AVP and cortisol. Iso was accompanied by the retention of water and electrolytes, whereas the Hyper load was excreted within 24 h. Natriuresis is attributed to increased filtration and is independent of an increase in atrial natriuretic peptide and decreases in ANG II and aldosterone. Fasting pups appear to have well-developed kidneys capable of both extreme conservation and excretion of Na(+).     

Acyl CoA profiles of transgenic plants that accumulate medium-chain fatty acids indicate inefficient storage lipid synthesis in developing oilseeds

Several Brassica napus lines transformed with genes responsible for the synthesis of medium- or long-chain fatty acids were examined to determine limiting factor(s) for the subsequent accumulation of these fatty acids in seed lipids. Examination of a decanoic acid (10:0) accumulating line revealed a disproportionately high concentration of 10:0 CoA during seed development compared to long-chain acyl CoAs isolated from the same tissues, suggesting that poor incorporation of 10:0 CoA into seed lipids limits 10:0 fatty acid accumulation. This relationship was also seen for dodecanoyl (12:0) CoA and fatty acid in a high 12:0 line, but not for octadecanoic (18:0) CoA and fatty acid in a high 18:0 line. Comparison of 10:0 CoA and fatty acid proportions from seeds at different developmental stages for transgenic B. napus and Cuphea hookeriana, the source plant for the medium-chain thioesterase and 3-ketoacyl-ACP synthase transgenes, revealed that C. hookeriana incorporates 10:0 CoA into seed lipids more efficiently than transgenic B. napus. Furthermore, beta-oxidation and glyoxylate cycle activities were not increased above wild type levels during seed development in the 8:0/10:0 line, suggesting that lipid catabolism was not being induced in response to the elevated 10:0 CoA concentrations. Taken together, these data suggest that transgenic plants that are engineered to synthesize medium-chain fatty acids may lack the necessary mechanisms, such as specific acyltransferases, to incorporate these fatty acids efficiently into seed lipids.     

Engineering oilseeds to produce nutritional fatty acids

There is a growing body of evidence suggesting that regular consumption of foods rich in omega-3 long chain polyunsaturated fatty acids has multiple positive health benefits. The fats and oils from marine fish contain high contents of these beneficial fatty acids but increased consumer demand has also increased strain on the ability of the world's fisheries to meet demand from wild capture. Many consumers are choosing fish oil supplements or are eating foods that have been complemented with fish oils instead of consuming fish directly. However, removing undesirable odors, flavors and contaminants is expensive. In contrast, oils derived from land plants such as soybean are inexpensive and contaminant free. Recent strides in plant molecular biology now allow the engineering of oilseeds for the production of novel fats and oils, including those synthesized by complex, multigene biosynthetic pathways such as the omega-3 long chain polyunsaturated fatty acids. Given the potential benefits to the environment with regards to overfishing and the health prospects of increased consumption of these healthy fatty acids, producing these fatty acids in oilseeds is a desirable and worthy goal. In this review, we will describe the recent advances in this field along with some of the technical hurdles encountered thus far.     

Changes in triacylglycerol, diacylglycerol and free fatty acids after fertilization in developing toad embryos

The content and fatty-acid composition of triacylglycerols, diacylglycerols and free fatty acids were analyzed from the unfertilized oocyte stage to the gastrula stage in the toad Bufo arenarum Hensel. Fertilization triggered a 30% and a 40% decrease in triacylglycerol and diacylglycerol, respectively. In contrast, free fatty acid increased continuously from oocyte to gastrula stage with an accumulation of palmitate predominating. However, the observed increase in free fatty acid was too small to account for the decreases in both neutral glycerides. The decrease in triacylglycerol might be a reflection of the activation of lipolytic enzymes and the subsequent oxidation of fatty acids to meet the increased metabolic energy requirements brought on by fertilization. The diminished diacylglycerol content due to fertilization may be accounted for, at least in part, by the utilization of diacylglycerol in the synthesis of membrane phospholipids, inasmuch as their decrease occurred simultaneously with an increase in phosphatidic acid. When cell-free homogenates taken from the three stages of development (unfertilized, fertilized and gastrula) were incubated in Tris-Ringer buffer for 90 min, free fatty acid accumulated. Triacylglycerol and diacylglycerol did not change substantially during this incubation period. This fact indicates that the free fatty acid released during incubation was not derived from neutral glycerides, but probably from membrane phospholipids. The release of free fatty acid was significantly greater in samples from the fertilized oocyte stage. The results described in this paper suggest that the synthesis of membrane phospholipids, including an enhanced turnover of the acyl moiety, plays a significant role in the metabolic events activated by fertilization.     

Sleep and wakefulness in Greenland seal pups

ECoG of both hemispheres, EOG, neck EMG and EKG were recorded in 2 white (age 10 days) and 2 gray pups (age 1 month) of harp seal. The active wakefulness occupied 23.4 +/- 3.8% of total recording time, the relaxed wakefulness--32.6 +/- 3.6%, drowsiness--4.8 +/- 1.1%, slow wave sleep--31.5 +/- 3.0%, paradoxical sleep--7.7 +/- 0.8%. The sleep cycle averaged 18.2 +/- 1.4 min. Interhemispheric asymmetry of the ECoG was not seen in all 4 pups. The respiration was fast and regular in the relaxed wakefulness, then long respiration pauses were alternated with episodes of hyperventilation during slow wave sleep and there was rare and irregular respiration in the paradoxical sleep. The heart rate was lowest during the paradoxical sleep. It is suggested that this pattern of sleep, allowing seals to delay their breathing during sleep for a long time may be considered as an adaptation to existence in freezing seas.     

Suburban development and change in vegetation nutritional status

In a study of species presence/absence and soil properties in bushland around northern Sydney, Clements (1983) found that species groupings were related to total soil phosphorus. This report presents analysis of foliage nutrient concentrations in species within these groupings. The highest concentrations of phosphorus, calcium, magnesium and potassium occurred in the suburban/disturbed group. The lowest overall concentrations were found in foliage from species in the dry sclerophyll communities. Mean foliage phosphorus was 0.099%, 0.125% and 0.042% for wet sclerophyll, disturbed and dry sclerophyll groups, respectively. Exotic species, particularly in disturbed environments, had the highest foliage nutrient concentrations. Results presented here showed that foliage nutrient concentrations are consistent with definitions of these groups on the basis of total soil phosphorus. These changes are considered to be important for management and conservation of bushland areas around Sydney.     

Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups

Northern elephant seal (Mirounga angustirostris) pups rely on the oxidation of fat stores as their primary source of energy during their 8- to 12-wk postweaning fast; however, potential endocrine mechanisms involved with this increased fat metabolism have yet to be examined. Therefore, 15 pups were serially blood sampled in the field during the first 7 wk of their postweaning fast to examine the changes in plasma concentrations of cortisol and thyroid hormones (TH), which are involved in fat metabolism in other mammals. Cortisol increased, indicating that it contributed to an increase in lipolysis. Increased total triiodothyronine (tT(3)) and thyroxine (tT(4)) may not reflect increased thyroid gland activity, but rather alterations in hormone metabolism. tT(3)-to-tT(4) ratio decreased, suggesting a decrease in thyroxine (T(4)) deiodination, whereas the negative correlation between total proteins and free T(4) suggests that the increase in free hormone is attributed to a decrease in binding globulins. Changes in TH are most similar to those observed during hibernation than starvation in mammals, suggesting that the metabolic adaptations to natural fasting are more similar to hibernation despite the fact these animals remain active throughout the fasting period.     

Fatty acid metabolism in fasting elephant seal pups

Summary The turnover of two plasma free fatty acids (FFA) were measured in 5 northern elephant seal pups (Mirounga angustirostris) after approximately 2 months of post-weaning fasting. Turnover was determined using simultaneous bolus injections of¹⁴C-palmitate,³H-oleate and Evans blue (EB) administered via an indwelling extradural intravertebral catheter. At this time in their natural fast, the seals exhibited plasma FFA levels and turnover values higher than reported for other marine mammals and most terrestrial carnivores. There was no consistent difference between plasma FFA turnover measured by palmitate or oleate tracers. The results imply that FFA metabolism is the primary source of energy during fasting. This is interesting in light of previous observations of minimal ketoacid accumulation and low levels of glucose and protein energy production during fasting in these juvenile seals.     

Long-chain polyunsaturated fatty acids in breast milk in La Plata, Argentina: relationship with maternal nutritional status

Milk fat is the major source of energy for breastfed infants; it also supplies polyunsaturated fatty acids (PUFAs) essential for the development of brain, retina, and other organs. Maternal nutritional status is critical for the newborn, and little information exists regarding the PUFA status of vulnerable populations living in Southern regions. We studied the relationship between maternal nourishment and milk fatty acid composition. Mother nutritional status (normal, overweight or obese) was estimated on the body mass index. Milk protein, total lipid, and fatty acid composition were determined. Milk protein was not affected by mother's nutritional status. In obese mothers an increase in lipid content, linoleic acid, total n-6 and total PUFAs was observed comparing to the other groups. Disregarding the nutritional status, the ratio n-6/n-3 fatty acids was very high and the 22:6n-3 content was very low, when compared with those of mothers from other countries. This finding led us to urge Public Health officers to promote changes in the dietary habits of nursing women.     

Molecular approach of gossypol-induced reproductive toxicity in male rabbits. Changes in seminal plasma amino acids and fatty acids

This study was done to evaluate the effects of two sublethal doses of gossypol (4 and 20 mg/kg of BW, every other day) on some amino and fatty acid concentrations in male rabbit seminal plasma. Rabbits were chosen as an experimental animal owing to the fact that they are excellent model for reproductive toxicological effects. The experiment lasted 16 weeks and included two periods: a treatment period (first 8 weeks) where the animals were given the tested product, and a recovery period (second 8 weeks) where all drugs were withdrawn. Results showed that total amino acids (TAA), total essential amino acids (EAA), total non-essential amino acids (non-EAA) and EAA/non-EAA ratio were decreased in a dose-dependent manner during gossypol treatment. The deleterious effect on TAA concentrations was mainly due to the reduction in total EAA. However, these concentrations regained their normal values after gossypol cessation. Basic, acidic, neutral amino acids and basic/acidic amino acids ratio decreased in a dose-dependent manner by gossypol treatment. Additionally, gossypol administration caused decreases in total unsaturated fatty acids (USFA) and increases in total saturated fatty acids (SFA) and the SFA/USFA ratio in a dose-dependent manner. During the recovery period, total SFA and USFA showed significant reduction and significant increase, respectively, after gossypol withdrawal. In conclusion, gossypol administration affected rabbit seminal plasma concentrations of amino and fatty acids in a dose-dependant manner. Gossypol reduced TAA, total EAA and total non-EAA. Additionally, gossypol caused decreases in total USFA and increases in total SFA. These deleterious effects were associated with poor-quality semen observed in our previous studies.     

Differential mobilization of blubber fatty acids in lactating Weddell seals: evidence for selective use

A major source of energy during lactation in mammals is provided through the mobilization of blubber fatty acids (FAs). We investigated the extent to which FAs were mobilized to support both maternal metabolic requirements and milk production in the Weddell seal and how this was reflected in the FA composition of the pup's blubber at the end of lactation (EL). FA composition of postpartum female blubber was similar in the 2 yr of study (2002 and 2003) but differed markedly by EL. Pup blubber FAs (at EL) were also different between years and did not match that of the mother's milk or blubber. Milk FA composition changed during lactation, which may have been a reflection of an increase in pup energy demands at different stages of development. In addition, there was evidence of feeding by some females during lactation, with higher levels of some FAs in the milk than in the blubber. Our results indicate that differential mobilization of FAs occurred in lactating Weddell seals and that this was related to total body lipid stores at postpartum. Furthermore, growing pups did not store FAs unmodified, providing evidence that selective use does occur and also that using FA composition to elucidate dietary sources may be problematic in growing individuals.     

Mortality in Grey seal pups: incidence and causes

Pup production and mortality of beach breeding Grey seals was studied at two contrasting types of rookery, the cliff-bound island of Ramsey, Dyfed, and the low, grassy island of Auskerry, Orkney. Thirty-five per cent of pups died on Ramsey compared with 14 % on Auskerry. Almost half of the Ramsey mortality was accounted for by animals being lost from the beaches so that they were not available for analysis. The main proximate causes of death revealed by post-mortem examination were starvation and infections. The other conditions which accounted for a small proportion of deaths were drowning, trauma, non-viability, stillbirths, atelectasis, dystokia and heart abnormality. Certain pathogens associated with disease were common to both sites, while others were specific to Ramsey or Auskerry.
The most important ultimate cause of pup deaths appeared to be failure of the mother/pup bond. The differences in levels of mortality between the sites is thought to be due to differences in the topography of the beaches. Pup survival on the narrow cliff-bound beaches, or in caves, on Ramsey was reduced either directly through pups being washed off, or indirectly by overcrowding of animals at high tide.     

Prevalence of allosuckling behaviour in Subantarctic fur seal pups

Non-offspring maternal care should be rare due to the high costs of raising offspring, particularly lactation, but nonetheless occurs in a variety of taxa. Misguided parental care, associated with recognition errors and/or inattentiveness by lactating females, has been hypothesized as an explanation for allolactation in mammals. In an extension of this hypothesis, we suggest that milk-stealing is parasitism instigated by non-filial offspring, and that maternal behaviour is of secondary interest in an evolutionary context if she is unaware of the interaction. We provide evidence for frequent milk-stealing attempts by Subantarctic fur seal (Arctocephalus tropicalis) pups, including an example of sustained non-maternal care (> three months) for one pup during the confirmed absence of his mother, leading to a weaning mass equal to the population mean. We also present only the second account of fostering/twins in the species at this locality. We suggest that rather than the hitherto suggested rare and anomalous behaviour, milk-stealing behaviour (while not always successful) is common.     

Revisiting delta-6 desaturase regulation by C18 unsaturated fatty acids,depending on the nutritional status

Dietary polyunsaturated fatty acids (PUFA) play a key role in regulating delta-6 desaturase (D6D), the key enzyme for long-chain PUFA biosynthesis. Nevertheless, the extent of their effects on this enzyme remains controversial and difficult to assess. It has been generally admitted that C18 unsaturated fatty acids (UFAs) regulate negatively delta-6 desaturase (D6D). This inhibition has been evidenced in regard to a high glucose/fat free (HG/FF) diet used in reference. However, several nutritional investigations did not evidence any inhibition of desaturases when feeding fatty acids.Because the choice of the basal diet appeared to be of primary importance in such experiments, our goal was to reconsider the specific role of dietary UFAs on D6D regulation, depending on nutritional conditions. For that, sixteen adult Wistar rats were fed purified linoleic acid, α-linolenic acid or oleic acid, included in one of two diets at 4% by weight: an HG/FF or a high starch base (HS) where the pure UFAs replaced a mixed vegetable oil. Our results showed first that D6D specific activity was significantly greater when measured in presence of an HG/FF than with an HS/4% vegetable oil diet. Secondly, we found that linoleic and alpha-linolenic acids added to HG/FF reduced the specific activity of D6D. In contrast, when pure UFAs were added to an HS base, D6D specific activities remained unchanged or increased. Concordant results were obtained on D6D mRNA expression.Altogether, this study evidenced the importance of the nutritional status in D6D regulation by C18 UFAs: when used as control, HG/FF diet stimulates D6D compared with a standard control diet containing starch and 4% fats, leading to an overestimation of the D6D regulation by UFAs. Then, UFAs should be considered as repressors for unsaturated fatty acid biosynthesis only in very specific nutritional conditions.