Isotopic homogeneity throughout the skin in small cetaceans

Rationale: Isotope ratios from skin samples have been widely used to study cetacean trophic ecology. Usually, isotopic skin uniformity has been assumed, despite the heterogeneity of this tissue. This study aims to investigate (1) regional isotopic variation within the skin in cetaceans, and (2) isotopic variation among internal tissues.Methods: Stable carbon (delta C-13 values) and nitrogen (delta N-15 values) isotope ratios were measured in 11 skin positions in 10 common dolphins (Delphinus delphis) and 9 striped dolphins (Stenella coeruleoalba). In addition, the isotope ratios in the muscle, liver and kidney of both species were determined and compared with those from the skin and from all tissues combined. The signatures were determined by means of elemental analyser/isotope ratio mass spectrometry (EA/IRMS).Results: In both species, no differences between isotope ratios of the skin positions were found. Moreover, the isotope ratios of skin were similar to those of muscle. In contrast, liver and kidney showed higher isotope ratios than muscle and skin.Conclusions: Isotopic homogeneity within the skin suggests that the isotope ratios of a sample from a specific skin position can be considered representative of the ratios from the entire skin tissue in dolphins. This conclusion validates the results of previous stable isotope analyses in dolphins that used skin samples as representative of the whole skin tissue. Isotopic similarities or dissimilarities among tissues should be considered when analysing different tissues and comparing results from the same or different species

Effects of Forest Fragmentation on Feather Corticosterone Levels in an Amazonian Avian Community

Summary . In the Amazon, the construction of hydroelectric dams is an emergent driver of biodiversity loss, creating numerous land-bridge islands, most of them unable to sustain an assemblage of bird species comparable to the intact forest. Although we understand the effects of forest fragmentation on species richness and distribution, we still need to uncover the physiological mechanisms underlying the success of organisms living in disturbed habitats. In this study, we used feather corticosterone levels as a measurement of physiological indicators of stress, evaluating whether corticosterone levels mirror the effects of habitat fragmentation on species occurrence. Since data suggest that smaller islands can reduce habitat suitability, increasing stress in birds that live within them, we predicted that birds living in smaller islands would present increased feather corticosterone levels. We captured birds in 13 islands of varying size and in two continuous forests and analysed feather corticosterone levels of 265 individuals from eight different species. Overall, our findings did not support the hypothesis that corticosterone varies in relation to island size, except for the Guianan Antwarbler Hypocnemis cantator, which presented the predicted pattern: decreasing feather corticosterone levels with increasing island size. These differences suggest that species respond differently to stressors driven by fragmentation. Further studies are necessary to assess the reliability of corticosterone levels as a physiological measurement of stress and to determine which parameters are useful to understand how insularisation caused by human activities may influence the resistance of avian populations to habitat disturbances. - Bicudo, T., Anciães, M., Arregui, L. & Gil, D. (2020). Effects of forest fragmentation on feather corticosterone levels in an Amazonian avian community. Ardeola, 67: 229-245.We also thank the National Council for Scientific and Technological Development – CNPq, for the Ciência sem Fronteiras scholarship to T.B. DG's research in Brazil was supported by a Ciência sem Fronteiras (CNPq) grant to Regina Macedo. DG was additionally funded by a grant from the Ministerio de Economía y Competitividad (CGL2014-55577R). TB receive a PhD scholarship from CAPES

Myoglobin concentration and oxygen stores in different functional muscle groups from three small cetacean species

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Arregui, M., Singleton, E. M., Saavedra, P., Pabst, D. A., Moore, M. J., Sierra, E., Rivero, M. A., Câmara, N., Niemeyer, M., Fahlman, A., McLellan, W. A., & Bernaldo de Quirós, Y. Myoglobin concentration and oxygen stores in different functional muscle groups from three small cetacean species. Animals, 11(2), (2021): 451, https://doi.org/10.3390/ani11020451.Compared with terrestrial mammals, marine mammals possess increased muscle myoglobin concentrations (Mb concentration, g Mb · 100g−1 muscle), enhancing their onboard oxygen (O2) stores and their aerobic dive limit. Although myoglobin is not homogeneously distributed, cetacean muscle O2 stores have been often determined by measuring Mb concentration from a single muscle sample (longissimus dorsi) and multiplying that value by the animal’s locomotor muscle or total muscle mass. This study serves to determine the accuracy of previous cetacean muscle O2 stores calculations. For that, body muscles from three delphinid species: Delphinus delphis, Stenella coeruleoalba, and Stenella frontalis, were dissected and weighed. Mb concentration was calculated from six muscles/muscle groups (epaxial, hypaxial and rectus abdominis; mastohumeralis; sternohyoideus; and dorsal scalenus), each representative of different functional groups (locomotion powering swimming, pectoral fin movement, feeding and respiration, respectively). Results demonstrated that the Mb concentration was heterogeneously distributed, being significantly higher in locomotor muscles. Locomotor muscles were the major contributors to total muscle O2 stores (mean 92.8%) due to their high Mb concentration and large muscle masses. Compared to this method, previous studies assuming homogenous Mb concentration distribution likely underestimated total muscle O2 stores by 10% when only considering locomotor muscles and overestimated them by 13% when total muscle mass was considered.This research was funded by the US Office of Naval Research N00014-13-1-0773, the Subprograma de Biodiversidad del Ministerio de Economía y Competitividad del Gobierno de España (MINECO CGL 2012-39681 and CGL2015-71498-P) and the Canary Islands Government, which has funded and provided support to the stranding network. M.A. is funded by the University Professor Formation fellowship from the Spanish Ministry of Education, and Y.B.d.Q. is funded by a postdoctoral fellowship from the University of Las Palmas de Gran Canaria

Establishment of a fish model to study gas-bubble lesions

Decompression sickness (DCS) is a clinical syndrome caused by the formation of systemic intravascular and extravascular gas bubbles. The presence of these bubbles in blood vessels is known as gas embolism. DCS has been described in humans and animals such as sea turtles and cetaceans. To delve deeper into DCS, experimental models in terrestrial mammals subjected to compression/decompression in a hyperbaric chamber have been used. Fish can suffer from gas bubble disease (GBD), characterized by the formation of intravascular and extravascular systemic gas bubbles, similarly to that observed in DCS. Given these similarities and the fact that fish develop this disease naturally in supersaturated water, they could be used as an alternative experimental model for the study of the pathophysiological aspect of gas bubbles. The objective of this study was to obtain a reproducible model for GBD in fish by an engineering system and a complete pathological study, validating this model for the study of the physiopathology of gas related lesions in DCS. A massive and severe GBD was achieved by exposing the fish for 18 h to TDG values of 162–163%, characterized by the presence of severe hemorrhages and the visualization of massive quantities of macroscopic and microscopic gas bubbles, systemically distributed, circulating through different large vessels of experimental fish. These pathological findings were the same as those described in small mammals for the study of explosive DCS by hyperbaric chamber, validating the translational usefulness of this first fish model to study the gas-bubbles lesions associated to DCS from a pathological standpoint

Genomics reveals the role of admixture in the evolution of structure among sperm whale populations within the Mediterranean Sea

In oceanic ecosystems, the nature of barriers to gene flow and the processes by which populations may become isolated are different from the terrestrial environment, and less well understood. In this study we investigate a highly mobile species (the sperm whale, Physeter macrocephalus) that is genetically differentiated between an open North Atlantic population and the populations in the Mediterranean Sea. We apply high-resolution single nucleotide polymorphism (SNP) analysis to study the nature of barriers to gene flow in this system, assessing the putative boundary into the Mediterranean (Strait of Gibraltar and Alboran Sea region), and including novel analyses on structuring among sperm whale populations within the Mediterranean basin. Our data support a recent founding of the Mediterranean population, around the time of the last glacial maximum, and show concerted historical demographic profiles in both the Atlantic and the Mediterranean. In each region there is evidence for a population decline around the time of the founder event. The largest decline was seen within the Mediterranean Sea where effective population size is substantially lower (especially in the eastern basin). While differentiation is strongest at the Atlantic/Mediterranean boundary, there is also weaker but significant differentiation between the eastern and western basins of the Mediterranean Sea. We propose, however, that the mechanisms are different. While post-founding gene flow was reduced between the Mediterranean and Atlantic populations, within the Mediterranean an important factor differentiating the basins is probably a greater degree of admixture between the western basin and the North Atlantic and some level of isolation between the western and eastern Mediterranean basins. Subdivision within the Mediterranean Sea exacerbates conservation concerns and will require consideration of what distinct impacts may affect populations in the two basins

Trophic position of dolphins tracks recent changes in the pelagic ecosystem of the Macaronesian region (NE Atlantic)

14 pages, 6 figures, 1 table.-- Open accessDolphins play a key role in marine food webs as predators of mid-trophic-level consumers. Because of their mobility and relatively long life span, they can be used as indicators oflarge-scale changes in the ecosystem. In this study, we calculated the trophic position (TP) of 5 dolphin species from the Canary, Madeira and Azores Islands using bulk and compound-specific stable isotope ratios from muscle tissue to assess trophic adaptations to recent changes in the availability of feeding resources. Dolphin TP values were then compared with those of 7 other species of cetaceans from this region. Analysis of stable nitrogen isotopes in amino acids of the common dolphin indicated non-significant effects of changes in the basal resources of the food web and thus supported the use of bulk samples for TP estimations. Dolphins occupied an intermediate TP (mean: 3.91 to 4.20) between fin (3.25) and sperm whales (4.95). Species-specific TP were equivalent among islands. However, TP increased for the common dolphin and decreased for the bottlenose dolphin (the latter also becoming more oceanic) between 2000 and 2018 in the Canary Islands. These results suggest different impacts of recent changes in the oceanography and in the pelagic food web of the Macaronesian region on the trophic ecology of dolphin speciesThis study was supported in part by the projects QLOCKS (PID2020-115620RB-I00), funded by MCIN/AEI/10.13039/501100011033 (Spain), MISTIC SEAS 2 (‘Applyinga subregional coherent and coordinated approach to the monitoring and assessment of marine biodiversity in Macaronesia for the second cycle of the MSFD’), funded by the Directorate General Environment of the European Commission (Grant Agreement No. 11.0661/2017/750679/SUB/ENV.C2), MISTIC SEAS 3 (‘Developing a coordinated approach for assessing Descriptor 4 via its linkages with D1 and other relevant descriptors in the Macaronesian subregion’), funded by the Directorate General Environment of the European Commission (Grant Agreement No. 110661/2018/794676/SUB/ENV.C2), RACAM (Rede de Arrojamentos de Cetáceos do Arquipélago da Madeira), implemented by the Madeira Whale Museum and funded by the Machico Municipality and projects MARCET (MAC/1.1b/149) and MARCET II (MAC/2.6c/392), both co-financed by EU Programme INTERREG MAC 2014−2020, and through the Commission (28-5307) for ‘Technical scientific advice for the protection of the marine environment: assessment and monitoring of marine strategies, monitoring of marine protected areas of state competence (2018−2021)’ of the Spanish Ministry of Economy and Competitiveness Demographic Challenge (MITECO). Data collection in the Azores was supported by FCT and FRCT through TRACE-PTDC/MAR/74071/2006, MAPCET-M2.1.2/F/012/2011, IF/00943/2013/CP1199/CT0001 (FEDER, COMPETE, QREN, POPH, ESF, Portuguese Ministry for Science and Education, Azores 2020 Operational Programme). M.A.S. was funded by SUMMEREU-H2020 GA 817806. M.A.S. and R.P. were funded by OP AZORES 2020, through the EU Fund 01-0145-FEDER-000140. Okeanos is funded by FCT (UIDB/05634/2020) and by the Regional Government of the Azores (M1.1.A/REEQ.CIENTÍFICO UI&D/2021/010). J.G. was supported by the Spanish National Programme Juan de la Cierva-Formación (MCIN/AEI/10.13039/501100011033 FJC2019-040016-I). This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S) to the Institute of Marine Science (ICM-CSIC)Peer reviewe

Identification of candidate Parkinson disease genes by integrating genome-wide association study, expression, and epigenetic data sets

Importance Substantial genome-wide association study (GWAS) work in Parkinson disease (PD) has led to the discovery of an increasing number of loci shown reliably to be associated with increased risk of disease. Improved understanding of the underlying genes and mechanisms at these loci will be key to understanding the pathogenesis of PD. Objective To investigate what genes and genomic processes underlie the risk of sporadic PD. Design and Setting This genetic association study used the bioinformatic tools Coloc and transcriptome-wide association study (TWAS) to integrate PD case-control GWAS data published in 2017 with expression data (from Braineac, the Genotype-Tissue Expression [GTEx], and CommonMind) and methylation data (derived from UK Parkinson brain samples) to uncover putative gene expression and splicing mechanisms associated with PD GWAS signals. Candidate genes were further characterized using cell-type specificity, weighted gene coexpression networks, and weighted protein-protein interaction networks. Main Outcomes and Measures It was hypothesized a priori that some genes underlying PD loci would alter PD risk through changes to expression, splicing, or methylation. Candidate genes are presented whose change in expression, splicing, or methylation are associated with risk of PD as well as the functional pathways and cell types in which these genes have an important role. Results Gene-level analysis of expression revealed 5 genes (WDR6 [OMIM 606031], CD38 [OMIM 107270], GPNMB [OMIM 604368], RAB29 [OMIM 603949], and TMEM163 [OMIM 618978]) that replicated using both Coloc and TWAS analyses in both the GTEx and Braineac expression data sets. A further 6 genes (ZRANB3 [OMIM 615655], PCGF3 [OMIM 617543], NEK1 [OMIM 604588], NUPL2 [NCBI 11097], GALC [OMIM 606890], and CTSB [OMIM 116810]) showed evidence of disease-associated splicing effects. Cell-type specificity analysis revealed that gene expression was overall more prevalent in glial cell types compared with neurons. The weighted gene coexpression performed on the GTEx data set showed that NUPL2 is a key gene in 3 modules implicated in catabolic processes associated with protein ubiquitination and in the ubiquitin-dependent protein catabolic process in the nucleus accumbens, caudate, and putamen. TMEM163 and ZRANB3 were both important in modules in the frontal cortex and caudate, respectively, indicating regulation of signaling and cell communication. Protein interactor analysis and simulations using random networks demonstrated that the candidate genes interact significantly more with known mendelian PD and parkinsonism proteins than would be expected by chance. Conclusions and Relevance Together, these results suggest that several candidate genes and pathways are associated with the findings observed in PD GWAS studies

Myoglobin Concentration and Oxygen Stores in Different Functional Muscle Groups from Three Small Cetacean Species

Compared with terrestrial mammals, marine mammals possess increased muscle myoglobin concentrations (Mb concentration, g Mb · 100g−1 muscle), enhancing their onboard oxygen (O2) stores and their aerobic dive limit. Although myoglobin is not homogeneously distributed, cetacean muscle O2 stores have been often determined by measuring Mb concentration from a single muscle sample (longissimus dorsi) and multiplying that value by the animal’s locomotor muscle or total muscle mass. This study serves to determine the accuracy of previous cetacean muscle O2 stores calculations. For that, body muscles from three delphinid species: Delphinus delphis, Stenella coeruleoalba, and Stenella frontalis, were dissected and weighed. Mb concentration was calculated from six muscles/muscle groups (epaxial, hypaxial and rectus abdominis; mastohumeralis; sternohyoideus; and dorsal scalenus), each representative of different functional groups (locomotion powering swimming, pectoral fin movement, feeding and respiration, respectively). Results demonstrated that the Mb concentration was heterogeneously distributed, being significantly higher in locomotor muscles. Locomotor muscles were the major contributors to total muscle O2 stores (mean 92.8%) due to their high Mb concentration and large muscle masses. Compared to this method, previous studies assuming homogenous Mb concentration distribution likely underestimated total muscle O2 stores by 10% when only considering locomotor muscles and overestimated them by 13% when total muscle mass was considered