Posts Tagged 'fish'

The effects of constant and fluctuating elevated pCO2 levels on oxygen uptake rates of coral reef fishes

Highlights

• Coral reefs exhibit natural, diel pCO2 fluctuations that are expected to increase.

• Few studies have examined effects of fluctuating pCO2 on adult coral reef fishes.

• We measured swimming, O2 uptake rates, aerobic scope, and various blood parameters.

• Performing under fluctuating pCO2 conditions may be less energetically-costly.

• Studies should use ecologically-relevant CO2 when predicting climate change impacts.

Abstract

Ocean acidification, resulting from increasing atmospheric carbon dioxide (CO2) emissions, can affect the physiological performance of some fishes. Most studies investigating ocean acidification have used stable pCO2 treatments based on open ocean predictions. However, nearshore systems can experience substantial spatial and temporal variations in pCO2. Notably, coral reefs are known to experience diel fluctuations in pCO2, which are expected to increase on average and in magnitude in the future. Though we know these variations exist, relatively few studies have included fluctuating treatments when examining the effects of ocean acidification conditions on coral reef species. To address this, we exposed two species of damselfishes, Amblyglyphidodon curacao and Acanthochromis polyacanthus, to ambient pCO2, a stable elevated pCO2 treatment, and two fluctuating pCO2 treatments (increasing and decreasing) over an 8 h period. Oxygen uptake rates were measured both while fish were swimming and resting at low-speed. These 8 h periods were followed by an exhaustive swimming test (Ucrit) and blood draw examining swimming metrics and haematological parameters contributing to oxygen transport. When A. polyacanthus were exposed to stable pCO2 conditions (ambient or elevated), they required more energy during the 8 h trial regardless of swimming type than fish exposed to either of the fluctuating pCO2 treatments (increasing or decreasing). These results were reflected in the oxygen uptake rates during the Ucrit tests, where fish exposed to fluctuating pCO2 treatments had a higher factorial aerobic scope than fish exposed to stable pCO2 treatments. By contrast, A. curacao showed no effect of pCO2 treatment on swimming or oxygen uptake metrics. Our results show that responses to stable versus fluctuating pCO2 differ between species – what is stressful for one species many not be stressful for another. Such asymmetries may have population- and community-level impacts under higher more variable pCO2 conditions in the future.

Continue reading ‘The effects of constant and fluctuating elevated pCO2 levels on oxygen uptake rates of coral reef fishes’

Transcriptional analysis reveals physiological response to acute acidification stress of barramundi Lates calcarifer (Bloch) in coastal areas

To understand the physiological response of estuarine fish to acidification, barramundi (Lates calcarifer) juveniles were exposed to acidified seawater in experimental conditions. The molecular response of barramundi to acidification stress was assessed by RNA-seq analysis. A total of 2188 genes were identified as differential expression genes. The gene ontology classification system and Kyoto Encyclopedia of Genes and Genomes database analysis showed that acidification caused differential expressions of genes and pathways in the gills of barramundi. Acidification had a great influence on the signal transduction pathway in cell process. Furthermore, we detected that numerous unigenes involved in the pathways associated with lipid metabolism, carbohydrate metabolism, amino acid metabolism, glycan biosynthesis and metabolism specific and non-specific immunity were changed. This study indicates that the physiological responses in barramundi especially the immune system and energy allocation correspond to the variation of environmental pH. This study reveals the necessity for assessment of the potential of estuarine fishes to cope with acidification of the environment and the need to develop strategies for fish conservation in coastal areas.

Continue reading ‘Transcriptional analysis reveals physiological response to acute acidification stress of barramundi Lates calcarifer (Bloch) in coastal areas’

The effect of environmental stressors on the development and behaviour of larval Oryzias latipes

Elevated water temperature and dissolved carbon dioxide (CO2) are two environmental stressors that freshwater organisms face in the Anthropocene. Larval fishes are particularly susceptible to elevation in water parameters, as they are often confined to rearing habitats where temperature and CO2 are nearing species-specific maxima. In this study, 240 freshwater Japanese medaka (Oryzias latipes) eggs were exposed to either control conditions (27˚C, ~ 500 µatm pCO2), elevated water temperature (36˚C), elevated CO2 (~1500 µatm pCO2) or both elevated temperature and CO2 (36˚C, ~1500 µatm pCO2). Exposures were applied either during the early, middle or late developmental stages and the morphological and behavioural data was collected ten days post-hatch. I predicted that elevated temperature and CO2 would decrease hatching success, and produce abnormalities in the swim bladder, spine or heart. In addition, I predicted that fish exposed to the stressors would show a change in swimming behaviour. Of the behavioural parameters observed, a significant difference was found in the distance travelled among the larval fish exposed to the treatments. There was no significant change between treatments or time intervals for hatching success, length or morphology. As rising CO2 and warming are likely to have a consequential impact on freshwater species, further research dedicated to understanding the ramification of climate-induced stressors is imperative.

Continue reading ‘The effect of environmental stressors on the development and behaviour of larval Oryzias latipes’

Fish embryo vulnerability to combined acidification and warming coincides with a low capacity for homeostatic regulation

The vulnerability of fish embryos and larvae to environmental factors is often attributed to a lack of adult-like organ systems (gills) and thus insufficient homeostatic capacity. However, experimental data supporting this hypothesis are scarce. Here, by using Atlantic cod (Gadus morhua) as a model, the relationship between embryo vulnerability (to projected ocean acidification and warming) and homeostatic capacity was explored through parallel analyses of stage-specific mortality and in vitro activity and expression of major ion pumps (ATP-synthase, Na+/K+-ATPase, H+-ATPase) and co-transporters (NBC1, NKCC1). Immunolocalization of these transporters was used to study ionocyte morphology in newly hatched larvae. Treatment-related embryo mortality until hatching (+20% due to acidification and warming) occurred primarily during an early period (gastrulation) characterized by extremely low ion transport capacity. Thereafter, embryo mortality decreased in parallel with an exponential increase in activity and expression of all investigated ion transporters. Significant changes in transporter activity and expression in response to acidification (+15% activity) and warming (−30% expression) indicate some potential for short-term acclimatization, although this is probably associated with energetic trade-offs. Interestingly, whole-larvae enzyme activity (supported by abundant epidermal ionocytes) reached levels similar to those previously measured in gill tissue of adult cod, suggesting that early-life stages without functional gills are better equipped in terms of ion homeostasis than previously thought. This study implies that the gastrulation period represents a critical transition from inherited (maternal) defenses to active homeostatic regulation, which facilitates enhanced resilience of later stages to environmental factors.

Continue reading ‘Fish embryo vulnerability to combined acidification and warming coincides with a low capacity for homeostatic regulation’

Anthropogenic stressors influence reproduction and development in elasmobranch fishes

The consequences of human influence can arise in vertebrates as primary, secondary, or even tertiary stressors and may be especially detrimental for slow growing species with long generation times (i.e., K-selected species). Here, we review the impacts of both direct and indirect human interactions on the reproductive biology of elasmobranchs. Within direct human influence, capture-induced stress from fisheries bycatch and poor coastal management practices leading to habitat destruction and pollution are among the most impactful on elasmobranch reproduction. Capture-induced stress has been shown to negatively influence offspring and reproductive capacity via capture-induced parturition as well as by disrupting the reproductive physiology of adults. Habitat degradation impacts essential ecosystems that are necessary for the development of young elasmobranchs. Pollutants such as heavy metals, legacy pesticides, and flame retardants have been traced through elasmobranch reproduction; however, the long-term effects of these exogenous chemicals are yet to be determined. Furthermore, within indirect human impacts, climate change-mediated influences (e.g., ocean warming and acidification) can impact development, physiological processes, and behavioral patterns necessary for essential tasks such as foraging, growth, reproduction, and ultimately survival. Here, we also present a case study, where data regarding temperature and incubation time from 28 egg-laying elasmobranch species were examined to show relevance of such data in predicting how suitable (e.g., via maximum threshold temperatures) habitats will be for skate and shark development in the coming century. Concomitantly, this information highlights areas for future research that will help inform better management as well as climate change forecasting for this threatened group of aquatic vertebrates.

Continue reading ‘Anthropogenic stressors influence reproduction and development in elasmobranch fishes’

Evolutionary links between intra‐ and extracellular acid–base regulation in fish and other aquatic animals

The acid–base relevant molecules carbon dioxide (CO2), protons (H+), and bicarbonate (HCO3) are substrates and end products of some of the most essential physiological functions including aerobic and anaerobic respiration, ATP hydrolysis, photosynthesis, and calcification. The structure and function of many enzymes and other macromolecules are highly sensitive to changes in pH, and thus maintaining acid–base homeostasis in the face of metabolic and environmental disturbances is essential for proper cellular function. On the other hand, CO2, H+, and HCO3 have regulatory effects on various proteins and processes, both directly through allosteric modulation and indirectly through signal transduction pathways. Life in aquatic environments presents organisms with distinct acid–base challenges that are not found in terrestrial environments. These include a relatively high CO2 relative to O2 solubility that prevents internal CO2/HCO3 accumulation to buffer pH, a lower O2 content that may favor anaerobic metabolism, and variable environmental CO2, pH and O2 levels that require dynamic adjustments in acid–base homeostatic mechanisms. Additionally, some aquatic animals purposely create acidic or alkaline microenvironments that drive specialized physiological functions. For example, acidifying mechanisms can enhance O2 delivery by red blood cells, lead to ammonia trapping for excretion or buoyancy purposes, or lead to CO2 accumulation to promote photosynthesis by endosymbiotic algae. On the other hand, alkalinizing mechanisms can serve to promote calcium carbonate skeletal formation. This nonexhaustive review summarizes some of the distinct acid–base homeostatic mechanisms that have evolved in aquatic organisms to meet the particular challenges of this environment.

Continue reading ‘Evolutionary links between intra‐ and extracellular acid–base regulation in fish and other aquatic animals’

Toward a mechanistic understanding of marine invertebrate behavior at elevated CO2

Elevated carbon dioxide (CO2) levels can alter ecologically important behaviors in a range of marine invertebrate taxa; however, a clear mechanistic understanding of these behavioral changes is lacking. The majority of mechanistic research on the behavioral effects of elevated CO2 has been done in fish, focusing on disrupted functioning of the GABAA receptor (a ligand-gated ion channel, LGIC). Yet, elevated CO2 could induce behavioral alterations through a range of mechanisms that disturb different components of the neurobiological pathway that produces behavior, including disrupted sensation, altered behavioral choices and disturbed LGIC-mediated neurotransmission. Here, we review the potential mechanisms by which elevated CO2 may affect marine invertebrate behaviors. Marine invertebrate acid–base physiology and pharmacology is discussed in relation to altered GABAA receptor functioning. Alternative mechanisms for behavioral change at elevated CO2 are considered and important topics for future research have been identified. A mechanistic understanding will be important to determine why there is variability in elevated CO2-induced behavioral alterations across marine invertebrate taxa, why some, but not other, behaviors are affected within a species and to identify which marine invertebrates will be most vulnerable to rising CO2 levels.

Continue reading ‘Toward a mechanistic understanding of marine invertebrate behavior at elevated CO2’

Proteomic responses to ocean acidification in the brain of juvenile coral reef fish

Elevated CO2 levels predicted to occur by the end of the century can affect the physiology and behaviour of marine fishes. For one important survival mechanism, the response to chemical alarm cues from conspecifics, substantial among-individual variation in the extent of behavioural impairment when exposed to elevated CO2 has been observed in previous studies. Whole brain transcriptomic data has further emphasized the importance of parental phenotypic variation in the response of juvenile fish to elevated CO2. In this study, we investigate the genome-wide proteomic responses of this variation in the brain of 5-week old spiny damselfish, Acanthochromis polyacanthus. We compared the expression of proteins in the brains of juvenile A. polyacanthus from two different parental behavioural phenotypes (sensitive and tolerant) that had been experimentally exposed to short-term, long-term and inter-generational elevated CO2. Our results show differential expression of key proteins related to stress response and epigenetic markers with elevated CO2 exposure. Proteins related to neurological development were also differentially expressed particularly in the long-term developmental treatment, which might be critical for juvenile development. By contrast, exposure to elevated CO2 in the parental generation resulted in only three differentially expressed proteins in the offspring, revealing potential for inter-generational acclimation. Lastly, we found a distinct proteomic pattern in juveniles due to the behavioural sensitivity of parents to elevated CO2, even though the behaviour of the juvenile fish was impaired regardless of parental phenotype. Our data shows that developing juveniles are affected in their brain protein expression by elevated CO2, but the effect varies with the length of exposure as well as due to variation of parental phenotypes in the population.

Continue reading ‘Proteomic responses to ocean acidification in the brain of juvenile coral reef fish’

Transgenerational regulation of cbln11 gene expression in the olfactory rosette of the European sea bass (Dicentrarchus labrax) exposed to ocean acidification

Highlights

Cbln11 mRNA is mainly expressed in the olfactory rosettes and in the gills of European sea bass.

Cbln11 mRNA expression is localized in the non-sensory epithelium of the olfactory rosettes.

•Long term exposure to ocean acidification induces a stimulation of cbln11 mRNA expression in the olfactory rosette of European sea bass.

•Ocean acidification-induced stimulation of cbln11 mRNA expression suggests a regulation of innate immune function.

Abstract

Elevated amounts of atmospheric CO2 are causing ocean acidification (OA) that may affect marine organisms including fish species. While several studies carried out in fish revealed that OA induces short term dysfunction in sensory systems including regulation of neurons activity in olfactory epithelium, information on the effects of OA on other physiological processes and actors is scarcer. In the present study we focused our attention on a European sea bass (Dicentrarchus labrax) sghC1q gene, a member of the C1q-domain-containing (C1qDC) protein family. In vertebrates, C1qDC family includes actors involved in different physiological processes including immune response and synaptic organization. Our microsynteny analysis revealed that this sghC1q gene is the orthologous gene in European sea bass to zebrafish (Danio rerio) cbln11 gene. We cloned the full length cbln11 mRNA and identified the different domains (the signal peptide, the coiled coil region and the globular C1q domain) of the deduced protein sequence. Investigation of mRNA expression by qPCR and in situ hybridization revealed that cbln11gene is especially expressed in the non-sensory epithelium of the olfactory rosette at larval and adult stages. The expression of cbln11 mRNA was analysed by qPCR in the first generation (F0) of European sea bass broodstock exposed since larval stages to water pH of 8.0 (control) or 7.6 (predicted for year 2100) and in their offspring (F1) maintained in the environmental conditions of their parents. Our results showed that cbln11 mRNA expression level was lower in larvae exposed to OA then up-regulated at adult stage in the olfactory rosette of F0 and that this up-regulation is maintained under OA at larval and juvenile stages in F1. Overall, this work provides evidence of a transgenerational inheritance of OA-induced up-regulation of cbln11 gene expression in European sea bass. Further studies will investigate the potential immune function of cbln11 gene and the consequences of these regulations, as well as the possible implications in terms of fitness and adaptation to OA in European sea bass.

Continue reading ‘Transgenerational regulation of cbln11 gene expression in the olfactory rosette of the European sea bass (Dicentrarchus labrax) exposed to ocean acidification’

Differential gene expression patterns related to lipid metabolism in response to ocean acidification in larvae and juveniles of Atlantic cod

Highlights

•Larvae upregulate genes associated with fatty acid and glycogen synthesis under moderate ocean acidification (OA)

•Larvae under high levels of OA fail to regulate

•Dysfunctional metabolism and stress associated with pathologies in internal organs

•Juveniles do not differentially regulate genes under OA, associated with higher resilience and lack of physiological response to OA as a stressor at this stage

Abstract

Elevated environmental carbon dioxide (pCO2) levels have been found to cause organ damage in the early life stages of different commercial fish species, including Atlantic cod (Gadus morhua). To illuminate the underlying mechanisms causing pathologies in the intestines, the kidney, the pancreas and the liver in response to elevated pCO2, we examined related gene expression patterns in Atlantic cod reared for two months under three different pCO2 regimes: 380 μatm (control), 1800 μatm (medium) and 4200 μatm (high). We extracted RNA from whole fish sampled during the larval (32 dph) and early juvenile stage (46 dph) for relative expression analysis of 18 different genes related to essential metabolic pathways. At 32 dph, larvae subjected to the medium treatment displayed an up-regulation of genes mainly associated with fatty acid and glycogen synthesis (GYS2, 6PGL, ACoA, CPTA1, FAS and PPAR1b). Larvae exposed to the high pCO2 treatment upregulated fewer but similar genes (6PGL, ACoA and PPAR1b,). These data suggest stress-induced alterations in the lipid and fatty acid metabolism and a disrupted lipid homeostasis in larvae, providing a mechanistic link to the findings of lipid droplet overload in the liver and organ pathologies. At 46 dph, no significant differences in gene expression were detected, confirming a higher resilience of juveniles in comparison to larvae when exposed to elevated pCO2 up to 4200 μatm.

Continue reading ‘Differential gene expression patterns related to lipid metabolism in response to ocean acidification in larvae and juveniles of Atlantic cod’

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Ocean acidification in the IPCC AR5 WG II

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