Aplicación de técnicas moleculares y químicas al estudio de la dieta, migración y estructura poblacional del rorcual común de Islandia

[spa] El objetivo global de esta tesis es ampliar el conocimiento sobre la biología y ecología del rorcual común, con foco principal en la población de rorcual común de Islandia. Dadas las numerosas incógnitas que siguen existiendo alrededor de esta especie, se establecen una serie de objetivos concretos que serán respondidos en los distintos capítulos. La presente tesis se divide en dos bloques principales. En el primer bloque, se aplicarán análisis de isótopos estables para responder preguntas principalmente relacionadas con la ecología trófica de la población de rorcual común de Islandia. Este bloque incluye los Capítulos 1 y 2. En el segundo bloque, se utilizarán los análisis de isótopos estables junto con los análisis de la metilación del ADN para analizar principalmente la estructura migratoria y poblacional del rorcual común de Islandia, comparándola en algunos estudios con la población de rorcual común de España. En este bloque también se analizará el uso de la metilación de ADN para determinar la edad de los rorcuales comunes. Este bloque incluye los Capítulos 3, 4 y 5. Los objetivos concretos establecidos en la presente tesis son: a. Determinar la repartición de los recursos ecológicos entre las especies de misticetos que se alimentan en aguas islandesas. En el Capítulo 1, se analizarán muestras de pieles de las cinco especies de misticetos (ballena azul, rorcual común, ballena jorobada, rorcual aliblanco y rorcual boreal), que se alimentan en aguas islandesas. Se determinarán los valores isotópicos del nitrógeno, carbono y azufre para inferir la dieta de cada especie y la posible competencia entre ellas. b. Explorar el uso de las barbas de ballena para estudiar los potenciales movimientos migratorios y cambios en la dieta, analizando el efecto que puede tener el tamaño de la barba y su posición en la boca del animal en los resultados obtenidos. En la primera parte del Capítulo 2, se examinará si los isótopos estables analizados en muestras de barbas procedentes de una misma ballena nos proporcionan la misma información, indistintamente de su tamaño y posición dentro de la boca del animal. Este estudio preliminar es de gran importancia de cara a los estudios posteriores en los cuales se utiliza esta metodología, y en los que no siempre se sabe la posición que ocupaba la barba analizada. c. Explorar la aplicabilidad de los isótopos de azufre en el estudio de los movimientos a escala oceánica del rorcual común Como se ha expuesto en la Introducción, los isótopos de azufre han sido utilizados principalmente para diferenciar comportamientos costeros de comportamientos pelágicos. Sin embargo, cuando han sido aplicados para analizar barbas de ballenas, han surgido dudas durante su interpretación. Nuevamente en el Capítulo 2, se analizarán los isótopos de azufre (junto con isótopos de nitrógeno y carbono) para estudiar su potencial aplicación a escala oceánica, concretamente para el estudio de las migraciones y los cambios de dieta del rorcual común. d. Determinar si existe algún tipo de estructuración en las migraciones del rorcual común de la población islandesa. Las migraciones y el comportamiento del rorcual común fuera de las zonas de alimentación son ampliamente desconocidas. En el Capítulo 3, a través de los análisis de isótopos del nitrógeno en barbas, se comprobará si existe estructura en las migraciones efectuadas por los individuos de la población islandesa. Además, se realizarán análisis genéticos para determinar el grado de parentesco de los individuos analizados. e. Comprobar la efectividad de la metilación en la determinación de la edad de los rorcuales comunes Determinar la edad de los individuos es un paso esencial para poder comprender la estructura poblacional. En el Capítulo 4, se realizará un modelo predictor de la edad para el rorcual común a partir de marcadores epigenéticos. Así mismo, se estudiará el posible efecto del ambiente en estos predictores. f. Determinar la existencia de diferencias epigenéticas entre dos poblaciones de rorcual común genéticamente homogéneas. En el Capítulo 5 se estudiarán las diferencias epigenéticas a nivel genómico que existen entre la población de Islandia y la población de España. A pesar de que existen multitud de evidencias sobre su aislamiento, hasta la fecha los marcadores moleculares no han permitido una correcta discriminación.[eng] The fin whale is one of the most common mysticetes inhabiting the North Atlantic and, as most baleen whales, undertakes annual migrations alternating high‐latitude summer feeding grounds with low‐latitude winter breeding grounds. Most of the information about the fin whale is collected during summer periods, when this species aggregates to feed. However, once the fin whale starts its migration and departs from the feeding grounds, there is an important gap of knowledge involving its migratory strategy, diet, and population structure. The main objective of this thesis is to expand the knowledge about the fin whale biology and ecology, focusing on the Icelandic fin whale population. To this aim, δ15N, δ13C and δ34S values were determined in skin and baleen plate samples, to obtain information about fin whale trophic ecology and migratory patterns. Also, DNA methylation was analyzed in skin samples of Icelandic and Spanish fin whales, to better understand the differentiation between both populations, and to also test the use of methylation levels to determine age of individuals. Results highlight that Icelandic fin whales strongly rely on krill during summer. In addition, a significant overlap of isotopic niches was detected between fin and blue whales. This interspecific competition may be mitigated by some degree of spatio-temporal segregation in the Icelandic waters, reflected in the δ34S values of both species. The information provided by the stable isotopes analyzed in baleen plates showed that most fin whales perform annual migrations, which were also reflected in their δ34S values. δ15N values showed high inter- individual variability, suggesting that fin whales disperse during winter. However, we found some pairs of individuals with no kinship showing nearly identical isotopic patterns for two consecutive years, indicating of long-term association. Finally, methylation analyses showed that three genes presented age-related variation, but these results did not allow to perform accurate epigenetic age estimations. In addition, fin whale populations from Iceland and Spain exhibited differentially methylated regions throughout their epigenomes. A considerable number of the genes associated to these regions were related to the circadian clock or other characteristics related to migration, probably reflecting differential migrations between individuals of both populations. Overall, results of this thesis contribute to better understand the behavior, ecology and population structure of the North Atlantic fin whale

An evaluation of whale skin differences and its suitability as a tissue for stable isotope analysis

Stable isotope analysis of whale skin has been recurrently used to assess diet and movement patterns. Such studies rely on the untested assumption that the stable isotope ratios in the small skin biopsies analysed are representative of those throughout the skin. In balaenopterids, the ventral skin looks notably different from that of the dorsal region, which is smoother and darker. To investigate possible differences in isotopic ratios throughout the skin, we collected and analysed samples from dorsal and ventral positions in 28 fin whales (Balaenoptera physalus). No significant differences were found between these two skin positions, which might suggest that whale skin is likely a homogeneous tissue. Thus, the isotopic ratios determined at a specific point may be representative of the whole skin in whales

Are stable isotope ratios and oscillations consistent in all baleen plates along the filtering apparatus? Validation of an increasingly used methodology

Rationale Baleen plates are anatomical structures composed of inert tissue that hang from the upper jaw in mysticetes. Baleen plates may differ in size and in coloration between different segments of the filtering row or between sides of the mouth. Concern has been raised that variation in baleen plate characteristics may reflect dissimilar structural composition and growth rates liable to affect stable isotope ratios and their oscillation patterns. Methods We measured stable carbon (δ13C values) and nitrogen (δ15N values) isotope ratios at intervals of 1 cm along the longitudinal axis of six baleen plates collected from different positions along the mouth of a fin whale. All samples were analysed using a continuous flow isotope ratio mass spectrometer. Generalized additive models were fitted to the data from each baleen plate and the results of the models were compared visually. Results A total of 206 samples were analysed. Visually, all baleen plates presented nearly identical oscillations, independent of the position or the coloration of the baleen plate. However, the variation in δ13C and δ15N values occurring between the different baleen plates was higher in the segments of oscillations exhibiting steeper slopes. Conclusions Differences in size between plates in an individual are due to differential erosion rates according to their position in the mouth. Therefore, the position of sampling along the baleen plate row should not be a reason for concern when conducting stable isotope studies

Ecological niche partitioning between baleen whales inhabiting Icelandic waters

The highly productive waters off Iceland are an important feeding ground for baleen whales. Five balaenopterid species coexist there during the summer feeding season: the blue whale, the fin whale, the sei whale, the humpback whale and the common minke whale. For capital breeders such as baleen whales, niche partitioning and reduced interspecific competition during their stay in the feeding grounds may be critical for the completion of their annual cycles and the long-term stability of populations. Coexistence often entails spatio-temporal or trophic segregation to avoid competitive exclusion. With the aim of studying how these species share habitat and trophic resources, we analyzed the δ13C, δ15N and δ34S values in skin samples. Bayesian stable isotope mixing models to calculate compositional mixture of food sources showed that most species segregate by consuming different prey. Segregation was further enhanced by some degree of spatio-temporal exclusion. Overall, clear ecological niche partitioning was apparent between all species except between blue and fin whales. All the species consumed krill and, except for the common minke whale, this was the dominant prey. Among baleen whales, common minke whales and humpback whales were the major predators of sand eel, capelin and herring. In humpback whales, a strong reliance on krill may explain the apparently low rates of local entanglement in fishing nets as compared to other areas. Except for the blue whale, all species have shown evidence of adapting to shifts in prey availability and thus suggested capacity to cope with variability. However, in a scenario of increasing environmental variability associated to global warming, the overlap between ecological niches may have to decrease to allow long-term coexistence

Niche partitioning amongst northwestern Mediterranean cetaceans using stable isotopes

Ten species of cetaceans coexist in the Mediterranean Sea, one of the richest seas in biodiversity and endemisms worldwide. The conservation status of Mediterranean cetaceans has been a concern for many years, particularly due to increasing anthropogenic threats such as global warming and overfishing. We established the stable isotopic niches of carbon, nitrogen, and sulphur for five species of cetaceans inhabiting the northwestern Mediterranean Sea to elucidate the mechanisms of coexistence. The fin whale exploited epipelagic habitats with a low trophic level; the bottlenose dolphin was mostly neritic and had a high trophic level; the Risso's dolphin was oceanic and fed bathypelagically and at a high trophic level; finally, the common and striped dolphins displayed epipelagic distributions and similarly intermediate trophic levels. The isotopic niches of all species were exclusive except the common and striped dolphins, whose niches overlapped by 25%. These results suggest that the majority of species avoid competitive exclusion by trophic or spatial segregation with the exception of striped and common dolphins, in which interspecific competition is apparent. It is suggested that this competition brought the striped dolphin to displace the common dolphin from part of its distribution range, restricting it to the southern fringe of the western Mediterranean and, particularly, to the Alboran Sea. In this area, coexistence of the two species would be permitted by some degree of spatial segregation between them and a remarkably high productivity, all which mitigate competition

CpG methylation frequency of TET2, GRIA2, and CDKN2A genes in the North Atlantic fin whale varies with age and between populations.

Recovery rates for baleen whales that were decimated by exploitation vary between species and populations. Age determination is critical for the understanding of recovery trends and population structure, but determining age in free-ranging individuals remains challenging. Recent research has suggested that the methylation level of some genes in skin samples may provide age determinations with accuracy. We selected nine CpG sites from three genes (TET2, CDKN2A, and GRIA2) and analyzed them in 40 skin samples from known-age individuals pertaining to two different populations of fin whales from the North Atlantic. We observed significant correlations with age in five CpG sites. We used three of these CpG sites to perform an epigenetic age estimation. Predictions had a standard deviation of 2.94, but regression between observed and predicted ages showed a clear underestimation for older fin whales. For further development, we suggest: (1) screening for new CpG sites associated with age that exhibit higher variability between individuals, and (2) including older animals whenever the sampling allows it. We also observed subtle, but significant differences between the two populations studied in one of the CpG sites (TET2_CpG + 21). We attributed these differences to genetic differences or to the dissimilar environments that affect both populations

Jet-hadron correlations measured relative to the second order event plane in Pb–Pb collisions at √sNN = 2.76 TeV

The Quark Gluon Plasma (QGP) produced in ultra relativistic heavy-ion collisions at the Large Hadron Collider (LHC) can be studied by measuring the modifications of jets formed by hard scattered partons which interact with the medium. We studied these modifications via angular correlations of jets with charged hadrons for jets with momenta 20 < pjetT < 40 GeV/c as a function of the associated particle momentum. The reaction plane fit (RPF) method is used in this analysis to remove the flow modulated background. The analysis of angular correlations for different orientations of the jet relative to the second order event plane allows for the study of the path length dependence of medium modifications to jets. We present the dependence of azimuthal angular correlations of charged hadrons with respect to the angle of the axis of a reconstructed jet relative to the event plane in Pb-Pb collisions at sNN−−−√ = 2.76 TeV. The dependence of particle yields associated with jets on the angle of the jet with respect to the event plane is presented. Correlations at different angles relative to the event plane are compared through ratios and differences of the yield. No dependence of the results on the angle of the jet with respect to the event plane is observed within uncertainties, which is consistent with no significant path length dependence of the medium modifications for this observable

Publisher Correction: Unveiling the strong interaction among hadrons at the LHC

Correction to: Nature https://doi.org/10.1038/s41586-020-3001-6Published online 09 December 2020 In Fig. 1c of this Article, owing to an error during the production process, the equation incorrectly began ‘C(k*, r*) = …’ instead of ‘C(k*) = …’. In addition, in affiliation 71 ‘Dipartimento di Fisica dell’Università degli studi di Bari Aldo Moro’ has been corrected to read ‘Dipartimento di Fisica dell’Università degli studi di Cagliari’. The original Article has been corrected online

Multiplicity dependence of π, K, and p production in pp collisions at √s = 13 TeV

This paper presents the measurements of π±, K±, p and p¯ transverse momentum (pT) spectra as a function of charged-particle multiplicity density in proton-proton (pp) collisions at s√ = 13 TeV with the ALICE detector at the LHC. Such study allows us to isolate the center-of-mass energy dependence of light-flavour particle production. The measurements reported here cover a pT range from 0.1 GeV/c to 20 GeV/c and are done in the rapidity interval |y|<0.5. The pT-differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at s√ = 7 TeV, which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the pT-integrated hadron-to-pion yield ratios measured in pp collisions at two different center-of-mass energies are consistent when compared at similar multiplicities. This also extends to strange and multi-strange hadrons, suggesting that, at LHC energies, particle hadrochemistry scales with particle multiplicity the same way under different collision energies and colliding systems