Body composition changes, metabolic fuel use and energy expenditure during extended fasting in subantarctic fur seal (Arctocephalus tropicalis) pups at Amsterdam Island

The fasting metabolism of 71- to 235-d-old subantarctic fur seal (Arctocephalus tropicalis) pups from Amsterdam Island, southern Indian Ocean, was investigated during the long foraging trips of their mothers. Body lipid reserves were proportionally greater in female than male pups and higher in postmoult (37%) than premoult (10%) animals. The mass-specific rate of mass loss did not differ between the sexes but was lower than observed in other species. Daily mass loss was estimated to 56% fat, 10% protein, and 34% water. The rate of protein catabolism (15 g d&minus;1) was negatively related to the size of initial lipid stores and accounted for 9% (&plusmn;1%) of total energy expenditure. However, body composition changes during the fast were not equal between the sexes, with females relying more on protein catabolism than males (11% and 5% of total energy expenditure, respectively). Energy expenditure (270 kJ kg&minus;1 d&minus;1) and metabolic water production (11.5 mL kg&minus;1 d&minus;1) rates are the lowest reported for an otariid species. These results suggest that subantarctic fur seal pups greatly reduce activity levels to lower energy expenditure in addition to adopting protein-sparing metabolic pathways in order to survive the extreme fasts they must endure on Amsterdam Island.<br /

Ontogeny of body size and shape of Antarctic and subantarctic fur seals

Pre- and post-weaning functional demands on body size and shape of mammals are often in conflict, especially in species where weaning involves a change of habitat. Compared with long lactations, brief lactations are expected to be associated with fast rates of development and attainment of adult traits. We describe allometry and growth for several morphological traits in two closely related fur seal species with large differences in lactation duration at a sympatric site. Longitudinal data were collected from Antarctic (Arctocephalus gazella (Peters, 1875); 120 d lactation) and subantarctic (Arctocephalus tropicalis (Gray, 1872); 300 d lactation) fur seals. Body mass was similar in neonates of both species, but A. gazella neonates were longer, less voluminous, and had larger foreflippers. The species were similar in rate of preweaning growth in body mass, but growth rates of linear variables were faster for A. gazella pups. Consequently, neonatal differences in body shape increased over lactation, and A. gazella pups approached adult body shape faster than did A. tropicalis pups. Our results indicate that preweaning growth is associated with significant changes in body shape, involving the acquisition of a longer, more slender body with larger foreflippers in A. gazella. These differences suggest that A. gazella pups are physically more mature at approximately 100 d of age (close to weaning age) than A. tropicalis pups of the same age<br /

A new method for qualitative multi-scale analysis of bacterial biofilms on filamentous fungal colonies using confocal and electron microscopy

Bacterial biofilms frequently form on fungal surfaces and can be involved in numerous bacterial-fungal interaction processes, such as metabolic cooperation, competition, or predation. The study of biofilms is important in many biological fields, including environmental science, food production, and medicine. However, few studies have focused on such bacterial biofilms, partially due to the difficulty of investigating them. Most of the methods for qualitative and quantitative biofilm analyses described in the literature are only suitable for biofilms forming on abiotic surfaces or on homogeneous and thin biotic surfaces, such as a monolayer of epithelial cells.While laser scanning confocal microscopy (LSCM) is often used to analyze in situ and in vivo biofilms, this technology becomes very challenging when applied to bacterial biofilms on fungal hyphae, due to the thickness and the three dimensions of the hyphal networks. To overcome this shortcoming, we developed a protocol combining microscopy with a method to limit the accumulation of hyphal layers in fungal colonies. Using this method, we were able to investigate the development of bacterial biofilms on fungal hyphae at multiple scales using both LSCM and scanning electron microscopy (SEM). This report describes the protocol, including microorganism cultures, bacterial biofilm formation conditions, biofilm staining, and LSCM and SEM visualizations

Milk isotopic values demonstrate that nursing fur seal pups are a full trophic level higher than their mothers †

RATIONALE: In mammals including humans, mother-to-offspring transfer of nutrients has been the focus of several isotopic studies. Measurement of δ N values of milk, the exclusive food of newborns. Surprisingly, little isotopic information is available on milk and its biochemical components (lipids and proteins). METHODS: Paired blood and milk samples from 10 lactating females and their pups were collected from two otariid species, the Antarctic and subantarctic fur seals. Tissue δ 13 C and δ 15 N values were measured using continuous-flow isotope ratio mass spectrometry (CFIRMS) on maternal and offspring blood, and on whole milk, lipid-free milk and milk lipids, thus allowing the calculation and comparison of apparent (maternal blood to offspring blood) and real (lipid-free milk to offspring blood) Δ 13 C and Δ 15 N values. RESULTS: In both fur seal species, the apparent Δ 13 C values averaged~0.0 ‰. Lipid-free milk was slightly 13 C-depleted compared with both maternal and pup blood and it was strongly 13 C-enriched (~6.3 ‰) compared with milk lipids. In contrast, the apparent and real Δ 15 N values averaged 1.2-1.4 and 2.6-3.0 ‰, respectively, the differences being explained by the~1.5 ‰ lower milk δ 15 N values than those of maternal blood. CONCLUSIONS: In fur seals, the low apparent Δ 15 N translated into a higher real Δ 15 N value, amounting to a full trophic level, which is in agreement with the almost never verified hypothesis that 15 N differences between mothers and their offsprings should reflect one complete trophic level. The study highlights the need to measure milk isotopic values to disentangle the nutritional mother-to-offspring relationships

Flash and grab : deep-diving southern elephant seals trigger anti-predator flashes in bioluminescent prey

Funding: Fondation BNP Paribas; Centre National d'Etudes Spatiales; Institut Polaire Français Paul Emile Victor; Natural Environment Research Council; H2020 Marie Skłodowska-Curie Actions.Bioluminescence, which occurs in approximately 80% of the world's mesopelagic fauna, can take the form of a low-intensity continuous glow (e.g. for counter-illumination or signalling) or fast repetitions of brighter anti-predatory flashes. The southern elephant seal (SES) is a major consumer of mesopelagic organisms, in particular the abundant myctophid fish, yet the fine-scale relationship between this predator's foraging behaviour and bioluminescent prey remains poorly understood. We hypothesised that brief, intense light emissions should be closely connected with prey strikes when the seal is targeting bioluminescent prey that reacts by emitting anti-predator flashes. To test this, we developed a biologging device containing a fast-sampling light sensor together with location and movement sensors to measure simultaneously anti-predator bioluminescent emissions and the predator's attack motions with a 20 ms resolution. Tags were deployed on female SES breeding at Kerguelen Islands and Península Valdés, Argentina. In situ light levels in combination with duration of prey capture attempts indicated that seals were targeting a variety of prey types. For some individuals, bioluminescent flashes occurred in a large proportion of prey strikes, with the timing of flashes closely connected with the predator's attack motion, suggestive of anti-predator emissions. Marked differences across individuals and location indicate that SES do exploit bioluminescent organisms but the proportion of these in the diet varies widely with location. The combination of wideband light and acceleration data provides new insight into where and when different prey types are encountered and how effectively they might be captured.Publisher PDFPeer reviewe

Absolute frequency measurement of an SF6 two-photon line using a femtosecond optical comb and sum-frequency generation

International audienceWe demonstrate a new simple technique to measure IR frequencies near 30 THz using a femtosecond (fs) laser optical comb and sum-frequency generation. The optical frequency is directly compared to the distance between two modes of the fs laser, and the resulting beat note is used to control this distance which depends only on the repetition rate fr of the fs laser. The absolute frequency of a CO2 laser stabilized onto an SF6 two-photon line has been measured for the first time. This line is an attractive alternative to the usual saturated absorption OsO4 resonances used for the stabilization of CO2 lasers. First results demonstrate a fractional Allan deviation of 3.10-14 at 1 s

First direct determination of the Boltzmann constant by an optical method

International audienceWe have recorded the Doppler profile of a well-isolated rovibrational line in the ν2 band of 14NH3. Ammonia gas was placed in an absorption cell thermalized by a water-ice bath. By extrapolating to zero pressure, we have deduced the Doppler width which gives a first measurement of the Boltzmann constant, kB, by laser spectroscopy. A relative uncertainty of 2x10-4 has been obtained. The present determination should be significantly improved in the near future and contribute to a new definition of the kelvin

Autumn movements of fin whales (Balaenoptera physalus) from Svalbard, Norway, revealed by satellite tracking

Insight into animal movements is essential for understanding habitat use by individuals as well as population processes and species life-history strategies. In this study, we instrumented 25 fin whales with ARGOS satellite-transmitters in Svalbard, Norway, to study their movement patterns and behaviour (Area Restricted Search (ARS), transiting or unknown) during boreal autumn/early winter. Ten of the whales stayed in the tagging area (most northerly location: 81.68°N) for their entire tracking periods (max 45 days). The other 15 whales moved in a south-westerly direction; the longest track ended off the coast of northern Africa (> 5000 km from the tagging location) after 96 days. The whales engaged in ARS behaviour intermittently throughout their southward migrations. During transit phases the whales moved quickly; one individual maintained an average horizontal speed of 9.3 km/h (travelling 223 km per day) for a period of a week. This study documents that: (1) some fin whales might remain at high latitudes during winter; (2) the whales that do migrate probably feed along the way; (3) they can maintain high transiting speed for long periods and; (4) one breeding area for this species is likely located in deep, warm water some 100 km west of Morocco.publishedVersio

Regulation of the mTOR signaling pathway: from laboratory bench to bedside and back again

Recent publications have moved us significantly closer to a complete understanding of the mammalian target of rapamycin (mTOR) signaling pathway, which plays a central role in the control of growth and metabolism and is dysregulated in a broad spectrum of human diseases, including cancer, tuberous sclerosis, diabetes, and cardiovascular and neurodegenerative diseases. Rapamycin-related mTOR inhibitors have shown clinical efficacy in several of these diseases, and novel inhibitors currently in development will be valuable tools for further dissections of the mTOR signaling network in human health and disease