Dysregulation of microRNAs may contribute to neurosensory impairment in Arctic cod (Boreogadus saida) following CO2 exposure

MicroRNAs (miRNAs) are epigenetic markers with a key role in post-transcriptional gene regulation. Several studies have described the dysregulation of miRNAs in temperature and hypoxic stress responses of marine organisms, but their role in the response to acidification conditions has remained relatively underexplored. We investigated the differential expression of miRNAs in whole brain tissue of Arctic cod (Boregogadus saida) exposed to elevated aqueous CO2 levels representative of future climate change predictions. We detected the expression of 17 miRNAs of interest that are either directly or indirectly associated with reduced auditory performance; 12 of the 17 miRNAs showed significant differential expression in high treatment vs. low (control) aqueous CO2 conditions. Target gene predictions indicated that these miRNAs are likely involved with inner ear maintenance, hair cell degradation, age-related hearing loss, neural inflammation, and injury. The highest differential expression was observed in mir-135b, which is linked with increased neural inflammation and injury that may be associated with neurosensory dysfunction. Collectively, these results elucidate the contributions of miRNA mechanisms underlying CO2-induced sensory deficits in fishes facing abiotic environmental change and suggest strong potential for this approach to yield novel insights into the mechanistic effects of climate change on marine organisms

Investigating Behaviour and Population Dynamics of Striped Marlin (Kajikia audax) from the Southwest Pacific Ocean with Satellite Tags

Behaviour and distribution of striped marlin within the southwest Pacific Ocean were investigated using electronic tagging data collected from 2005–2008. A continuous-time correlated random-walk Kalman filter was used to integrate double-tagging data exhibiting variable error structures into movement trajectories composed of regular time-steps. This state-space trajectory integration approach improved longitude and latitude error distributions by 38.5 km and 22.2 km respectively. Using these trajectories as inputs, a behavioural classification model was developed to infer when, and where, ‘transiting’ and ‘area-restricted’ (ARB) pseudo-behavioural states occurred. ARB tended to occur at shallower depths (108±49 m) than did transiting behaviours (127±57 m). A 16 day post-release period of diminished ARB activity suggests that patterns of behaviour were affected by the capture and/or tagging events, implying that tagged animals may exhibit atypical behaviour upon release. The striped marlin in this study dove deeper and spent greater time at ≥200 m depth than those in the central and eastern Pacific Ocean. As marlin reached tropical latitudes (20–21°S) they consistently reversed directions, increased swimming speed and shifted to transiting behaviour. Reversals in the tropics also coincided with increases in swimming depth, including increased time ≥250 m. Our research provides enhanced understanding of the behavioural ecology of striped marlin. This has implications for the effectiveness of spatially explicit population models and we demonstrate the need to consider geographic variation when standardizing CPUE by depth, and provide data to inform natural and recreational fishing mortality parameters

The African Cichlid Fish Astatotilapia burtoni Uses Acoustic Communication for Reproduction: Sound Production, Hearing, and Behavioral Significance

Sexual reproduction in all animals depends on effective communication between signalers and receivers. Many fish species, especially the African cichlids, are well known for their bright coloration and the importance of visual signaling during courtship and mate choice, but little is known about what role acoustic communication plays during mating and how it contributes to sexual selection in this phenotypically diverse group of vertebrates. Here we examined acoustic communication during reproduction in the social cichlid fish, Astatotilapia burtoni. We characterized the sounds and associated behaviors produced by dominant males during courtship, tested for differences in hearing ability associated with female reproductive state and male social status, and then tested the hypothesis that female mate preference is influenced by male sound production. We show that dominant males produce intentional courtship sounds in close proximity to females, and that sounds are spectrally similar to their hearing abilities. Females were 2–5-fold more sensitive to low frequency sounds in the spectral range of male courtship sounds when they were sexually-receptive compared to during the mouthbrooding parental phase. Hearing thresholds were also negatively correlated with circulating sex-steroid levels in females but positively correlated in males, suggesting a potential role for steroids in reproductive-state auditory plasticity. Behavioral experiments showed that receptive females preferred to affiliate with males that were associated with playback of courtship sounds compared to noise controls, indicating that acoustic information is likely important for female mate choice. These data show for the first time in a Tanganyikan cichlid that acoustic communication is important during reproduction as part of a multimodal signaling repertoire, and that perception of auditory information changes depending on the animal's internal physiological state. Our results highlight the importance of examining non-visual sensory modalities as potential substrates for sexual selection contributing to the incredible phenotypic diversity of African cichlid fishes

Comparative metabolic rates of common western North Atlantic Ocean sciaenid fishes

The resting metabolic rates (RR) of western North Atlantic Ocean sciaenids, such as Atlantic croaker Micropogonias undulatus, spot Leiostomus xanthurus and kingfishes Menticirrhus spp., as well as the active metabolic rates (RA) of M. undulatus and L. xanthurus were investigated to facilitate inter and intraspecific comparisons of their energetic ecology. The RR of M. undulatus and L. xanthurus were typical for fishes with similar lifestyles. The RR of Menticirrhus spp. were elevated relative to those of M. undulatus and L. xanthurus, but below those of high-energy-demand species such as tunas Thunnus spp. and dolphinfish Coryphaena hippurus. Repeated-measures non-linear mixed-effects models were applied to account for within-individual autocorrelation and corrected for non-constant variance typical of noisy RA data sets. Repeated-measures models incorporating autoregressive first-order [AR(1)] and autoregressive moving average (ARMA) covariances provided significantly superior fits, more precise parameter estimates (i.e. reduced s.e.) and y-intercept estimates that more closely approximated measured RR for M. undulatus and L. xanthurus than standard least-squares regression procedures

Investigation of the origin of deep levels in CdTe doped with Bi

Combining optical (low temperature photoluminescence), electrical (thermoelectric effect spectroscopy), and structural (synchrotron X-ray powder diffraction) methods, the defect structure of CdTe doped with Bi was studied in crystals with dopant concentration in the range of 1017–1019 at./cm3. The semi-insulating state observed in crystals with low Bi concentration is assigned to the formation of a shallow donor level and a deep donor recombination center. Studying the evolution of lattice parameter with temperature, we postulate that the deep center is formed by a Te–Te dimer and their formation is explained by a tetrahedral to octahedral distortion, due to the introduction of Bi in the CdTe lattice. We also shows that this model agrees with the electrical, optical, and transport charge properties of the samples.This work has been partly supported by the projects CAM SENSORCDT S-0505/MAT/0209, CAM FOTOFLEX S-0505/ENE-123, and EU FP6 PHOLOGIC 017158. The authors are grateful to the European Synchrotron Radiation Facility (ESRF) for the experiments HS-3183 and HS-3184 and to Dr. German Castro. E.S. also thanks to the MEC of Spain for the fellowship FPU 2003-1388.Peer reviewe

Characterization of optical and electrical properties of CdTe:Yb co-doped with Ge

The defect structure of CdTe doped with Yb and co-doped with Ge was investigated by a set of optical (photoluminescence, absorption, photoconductivity), galvanomagnetic and thermoelectric methods. The results can be explained by a model, in which Yb acts as a deep donor with the energy level at EV+0.3 eV corresponding to the Yb2+/Yb3+ electronic transition. Introduction of Yb with concentration 1019 cm-3 in the melt results in a decrease of electrically and optically active acceptor defects in the as-grown crystals and causes a decrease of electrical resistivity of CdTe:Ge. A line at 1.585 eV related to an exciton bound to a complex of Yb and Cd vacancy was observed both in photoluminescence and photoconductivity spectra. © 2005 Elsevier B.V. Al l rights reserved.Peer Reviewe

Energy resolution studies of Ce- and Pr-doped aluminum and multicomponent garnets: The escape and photo-peaks

The photopeak and escape peak processes were studied in heavy $Ce^{3+}$ -doped LuAG and GGAG, $Pr^{3+}$ -doped LuAG and undoped BGO scintillating crystals. Energy resolution measurements were performed with 511 keV photons of $^{22}$Na radioisotope. In the pulse-height spectra the escape peaks were resolved clearly on thin samples (up to 3 mm). If sample thickness increases the escape peak cannot be resolved anymore (for thicknesses approx. above 5 mm, especially). Consequently, energy resolution increases by about 40% compared with that measured at 1 mm thick samples