Rapid increase in Adelie penguin populations in the Lutzow-Holm Bay area since the mid 1990s

The Adelie penguin, Pygoscelis adeliae, an important component of the Antarctic marine ecosystem, is closely associated with sea ice. Ten breeding populations along the Soya Coast of Lutzow-Holm Bay have been monitored since the 1960s by the Japanese Antarctic Research Expedition and shown to be increasing. In most colonies, small peaks of population increase were observed in the late 1980s with a rapid increase from the mid 1990s. Frequent sea ice break-ups in Lutzow-Holm Bay in the mid 1980s and since the late 1990s are thought to have induced the population increase through increased subadult survival and preferred prey availability. Population monitoring therefore needs to be continued carefully in relation to the environmental changes

Are stomach temperature recorders a useful tool for determining feeding activity?

Despite a number of limitations, stomach temperature recorders are still commonly used to determine feeding activity in free-ranging marine predators. In this regard, it is important to improve the detection rate of these systems by, for instance, increasing the probability that a cold prey touches the sensors. In the present study, we compared the detection rates and mass estimations of water and fish prey ingested by captive king penguins using a two-point temperature recorder (STL) and a single, but large, point recorder (SICUP). Prey items were of different masses (5-45 g) and delivered at different frequencies (high vs. low). Ingestions were recorded as precipitous drop followed by an exponential rise (PDER). Overall, 57.9, 56.0 and 70.0% of the ingestions were detected by the SICUP and the upper and lower sensors of the STL, respectively. Our study confirmed that employing two sensors improves the detection of prey ingestion, but the detection of very small prey items remains insufficient and prey items swallowed at short intervals are detected as cumulative ingestion events. Nonetheless, the total mass of food ingested can be estimated with more than 70% confidence

Diving angle of great cormorants

Seabirds can maximize the relative time spent at depths where prey occur by minimizing the commuting time taken to reach these depths. One way to achieve this goal is to modify dive angle, but there are few measures of dive-angle in free-foraging seabirds. In 2003, we monitored simultaneously the swimming speeds and diving depths of great cormorants (Phalacrocorax carbo) foraging off the Greenland coast, and used these data to reconstruct their descent angle. Both males and females dived on average 12 m. We suggest that birds are able to reduce their descent time for dives beyond this depth by performing pre-dive leaps that allow them to use the momentum of the fall to descend almost vertically and at great speeds. Such pre-dive leaps in shallower dives would be unsuitable because of the proximity of the seabed and the risk of startling prey. Finally, in contrast with deeper divers, descent angles were not steeper when undulations were observed in the depth profile of the previous dive, probably because birds feed on dispersed prey

Stress responsive miR-23a attenuates skeletal muscle atrophy by targeting MAFbx /atrogin-1

Muscle atrophy occurs in many pathological states and results primarily from accelerated protein degradation by the ubiquitin-proteasome pathway. We used dexamethasone to induce muscle wasting and investigated the role of a microRNA (miRNA) in the control of muscle-specific E3 ubiquitin ligase MAFbx/atrogin-1. Here we show that miR-23a suppresses MAFbx/atrogin-1 translation by binding to 3'UTR of the mRNA. Furthermore, ectopic expression of miR-23a is sufficient to protect myocytes from atrophy in vitro and in vivo in response to dexamethasone treatment, and heat stress-induced miR-23a protects muscle from dexamethasone-induced muscle atrophy. Our surprising discovery of the physiological role of miR-23a in preventing the atrophy program should lay the basis not only for further understanding of the mechanisms of muscle wasting in diverse diseases, but also for developing novel therapies for these debilitating conditions

Bio-logging science: sensing beyond the boundaries

Bio-logging has emerged as a tool in animal biology much as genomics has emerged as a tool in the study of cellular and organ function. Bio-logging is certain to increase in its importance and to influence the way we study events and processes that are beyond the usual boundaries of perception and that are remote from the observer. It is providing insights into the behaviour and function of organisms in environments that are hostile to the observer and in natural situations. In terms of the way that data are collected it has much in common with remote sensing and Earth observation. This includes post hoc analysis and interpretation of extensive data sets involving a low diversity of measured variables. Owing to the sparseness of data sets, practitioners need to develop better methods of applying the data to models of the organisms being studied. Although increasing technological sophistication is leading to collection of a greater diversity of variables, this also brings complications of interpreting multi-dimension data sets. Although it appears that technology currently constrains the type of biological questions that can be addressed, there is a danger that technological advancement could result in a loss of focus on hypothesis testing. There is evidence that the discipline of bio-logging is developing a substructure within which specialist teams of modellers, theoretical and field biologists, and engineers collaborate to address complex biological questions

Evolution of gaseous disk viscosity driven by supernova explosion in star-forming galaxies at high redshift

Motivated by Genzel et al.'s observations of high-redshift star-forming galaxies, containing clumpy and turbulent rings or disks, we build a set of equations describing the dynamical evolution of gaseous disks with inclusion of star formation and its feedback. Transport of angular momentum is due to "turbulent" viscosity induced by supernova explosions in the star formation region. Analytical solutions of the equations are found for the initial cases of a gaseous ring and the integrated form for a gaseous disk, respectively. For a ring with enough low viscosity, it evolves in a slow processes of gaseous diffusion and star formation near the initial radius. For a high viscosity, the ring rapidly diffuses in the early phase. The diffusion drives the ring into a region with a low viscosity and start the second phase undergoing pile-up of gas at a radius following the decreased viscosity torque. The third is a sharply deceasing phase because of star formation consumption of gas and efficient transportation of gas inward forming a stellar disk. We apply the model to two $z\sim 2$ galaxies BX 482 and BzK 6004, and find that they are undergoing a decline in their star formation activity.Comment: To appear in ApJ, 5 figure

Buoyancy under Control: Underwater Locomotor Performance in a Deep Diving Seabird Suggests Respiratory Strategies for Reducing Foraging Effort

BACKGROUND: Because they have air stored in many body compartments, diving seabirds are expected to exhibit efficient behavioural strategies for reducing costs related to buoyancy control. We study the underwater locomotor activity of a deep-diving species from the Cormorant family (Kerguelen shag) and report locomotor adjustments to the change of buoyancy with depth. METHODOLOGY/PRINCIPAL FINDINGS: Using accelerometers, we show that during both the descent and ascent phases of dives, shags modelled their acceleration and stroking activity on the natural variation of buoyancy with depth. For example, during the descent phase, birds increased swim speed with depth. But in parallel, and with a decay constant similar to the one in the equation explaining the decrease of buoyancy with depth, they decreased foot-stroke frequency exponentially, a behaviour that enables birds to reduce oxygen consumption. During ascent, birds also reduced locomotor cost by ascending passively. We considered the depth at which they started gliding as a proxy to their depth of neutral buoyancy. This depth increased with maximum dive depth. As an explanation for this, we propose that shags adjust their buoyancy to depth by varying the amount of respiratory air they dive with. CONCLUSIONS/SIGNIFICANCE: Calculations based on known values of stored body oxygen volumes and on deep-diving metabolic rates in avian divers suggest that the variations of volume of respiratory oxygen associated with a respiration mediated buoyancy control only influence aerobic dive duration moderately. Therefore, we propose that an advantage in cormorants--as in other families of diving seabirds--of respiratory air volume adjustment upon diving could be related less to increasing time of submergence, through an increased volume of body oxygen stores, than to reducing the locomotor costs of buoyancy control