Recent advances in telemetry for estimating the energy metabolism of wild fishes

Metabolic rate is a critical factor in animal biology and ecology, providing an objective measure that can be used in attributing a cost to different activities and to assessing what animals do against some optimal behaviour. Ideally, metabolic rate would be estimated directly by measuring heat output but, until recently, this has not been easily tractable with shes so instead metabolic rate is usually esti- mated using indirect methods. In the laboratory, oxygen consumption rate is the indirect method most frequently used for estimating metabolic rate, but technical requirements preclude the measurement of either heat output or oxygen consumption rate in free-ranging shes. There are other eld methods for estimating metabolic rate that can be used with mammals and birds but, again, these cannot be used with shes. Here, the use of electronic devices that record body acceleration in three dimensions (accelerometry) is considered. Accelerometry is a comparatively new telemetric method for assessing energy metabolism in animals. Correlations between dynamic body acceleration (DBA) and oxygen consumption rate demonstrate that this will be a useful proxy for estimating activity-speci c energy expenditure from shes in mesocosm or eld studies over extended periods where other methods (e.g. oxygen consumption rate) are not feasible. DBA therefore has potential as a valuable tool for attribut- ing cost to different activities. This could help in gaining a full picture of how shes make energy-based trade-offs between different levels of activity when faced with con icting or competing demands aris- ing from increased and combined environmental stressors

Preliminary study of kaonic deuterium X-rays by the SIDDHARTA experiment at DAFNE

The study of the KbarN system at very low energies plays a key role for the understanding of the strong interaction between hadrons in the strangeness sector. At the DAFNE electron-positron collider of Laboratori Nazionali di Frascati we studied kaonic atoms with Z=1 and Z=2, taking advantage of the low-energy charged kaons from Phi-mesons decaying nearly at rest. The SIDDHARTA experiment used X-ray spectroscopy of the kaonic atoms to determine the transition yields and the strong interaction induced shift and width of the lowest experimentally accessible level (1s for H and D and 2p for He). Shift and width are connected to the real and imaginary part of the scattering length. To disentangle the isospin dependent scattering lengths of the antikaon-nucleon interaction, measurements of Kp and of Kd are needed. We report here on an exploratory deuterium measurement, from which a limit for the yield of the K-series transitions was derived: Y(K_tot)<0.0143 and Y(K_alpha)<0.0039 (CL 90%). Also, the upcoming SIDDHARTA-2 kaonic deuterium experiment is introduced.Comment: Accepted by Nuclear Physics

X-ray transition yields of low-Z kaonic atoms produced in Kapton

The X-ray transition yields of kaonic atoms produced in Kapton polyimide (C22H10N2O5) were measured for the first time in the SIDDHARTA experiment. X-ray yields of the kaonic atoms with low atomic numbers (Z = 6, 7, and 8) and transitions with high principal quantum numbers (n = 5-8) were determined. The relative yield ratios of the successive transitions and those of carbon-to-nitrogen (C:N) and carbon-to-oxygen (C:O) were also determined. These X-ray yields provide important information for understanding the capture ratios and cascade mechanisms of kaonic atoms produced in a compound material, such as Kapton.Comment: Accepted in Nucl. Phys. A (2013

First measurement of kaonic helium-3 X-rays

The first observation of the kaonic 3He 3d - 2p transition was made using slow K- mesons stopped in a gaseous 3He target. The kaonic atom X-rays were detected with large-area silicon drift detectors using the timing information of the K+K- pairs of phi-meson decays produced by the DAFNE e+e- collider. The strong interaction shift of the kaonic 3He 2p state was determined to be -2+-2 (stat)+-4 (syst) eV.Comment: Accepted for publication in Phys. Lett.

Detailed analysis of zebrafish larval behaviour in the light dark challenge assay shows that diel hatching time determines individual variation

Research on stress coping style, i.e., the response of an organism to adverse conditions, which is constant over time and context, gained momentum in recent years, to better understand behavioural patterns in animal welfare. However, knowledge about the ontogeny of stress coping style is still limited. Here, we performed a detailed analysis of the light dark challenge behavioural assay in zebrafish larvae, where after acclimation in ambient light sudden alternating dark and light phases elicit an anxiety-like response. A principal component analysis on parameters related to locomotion (distance moved, swimming velocity, acceleration, mobility) and directionality (angular velocity, meandering of swimming path) revealed independence between the parameters determined in the light and the dark phases of the assay, indicating unrelated generalised behaviours per phase. However, high collinearity was observed between behavioural parameters within the same phase, indicating a robust response to the stimulus within behavioural phenotypes. Subsequently, this assay was used to determine the correlation between individual hatching time and the behavioural phenotype. The results show that fish that had hatched during daytime have a stronger behavioural response to the dark phase at 5 days post-fertilisation in locomotion related parameters and a weaker response in directionality related parameters, than fish that had hatched during nighttime. These results show that behavioural responses to the light dark challenge assay are robust and can be generalised for the light and the dark phase, and that diel hatching time may determine the behavioural phenotype of an individual.Animal science

Polystyrene nanoplastics disrupt glucose metabolism and cortisol levels with a possible link to behavioural changes in larval zebrafish

Plastic nanoparticles originating from weathering plastic waste are emerging contaminants in aquatic environments, with unknown modes of action in aquatic organisms. Recent studies suggest that internalised nanoplastics may disrupt processes related to energy metabolism. Such disruption can be crucial for organisms during development and may ultimately lead to changes in behaviour. Here, we investigated the link between polystyrene nanoplastic (PSNP)-induced signalling events and behavioural changes. Larval zebrafish exhibited PSNP accumulation in the pancreas, which coincided with a decreased glucose level. By using hyperglycemic and glucocorticoid receptor (Gr) mutant larvae, we demonstrate that the PSNP-induced disruption in glucose homoeostasis coincided with increased cortisol secretion and hyperactivity in challenge phases. Our work sheds new light on a potential mechanism underlying nanoplastics toxicity in fish, suggesting that the adverse effect of PSNPs are at least in part mediated by Gr activation in response to disrupted glucose homeostasis, ultimately leading to aberrant locomotor activity

A New Measurement of Kaonic Hydrogen X rays

The $\bar{K}N$ system at threshold is a sensitive testing ground for low energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we have measured the $K$-series x rays of kaonic hydrogen atoms at the DA$\Phi$NE electron-positron collider of Laboratori Nazionali di Frascati, and have determined the most precise values of the strong-interaction energy-level shift and width of the $1s$ atomic state. As x-ray detectors, we used large-area silicon drift detectors having excellent energy and timing resolution, which were developed especially for the SIDDHARTA experiment. The shift and width were determined to be $\epsilon_{1s} = -283 \pm 36 \pm 6 {(syst)}$ eV and $\Gamma_{1s} = 541 \pm 89 {(stat)} \pm 22 {(syst)}$ eV, respectively. The new values will provide vital constraints on the theoretical description of the low-energy $\bar{K}N$ interaction.Comment: 5 figures, submitted to Physics Letters

The role of the glucocorticoid receptor in the regulation of diel rhythmicity

Microbial Biotechnolog