Neural effects of elevated CO2 in fish may be amplified by a vicious cycle

Maladaptive behavioural disturbances have been reported in some fishes and aquatic invertebrates exposed to projected future CO2 levels. These disturbances have been linked to altered ion gradients and neurotransmitter function in the brain. Still, it seems surprising that the relatively small ionic changes induced by near-future CO2 levels can have such profound neural effects. Based on recent transcriptomics data, we propose that a vicious cycle can be triggered that amplifies the initial disturbance, explaining howsmall pH regulatory adjustments in response to ocean acidification can lead to major behavioural alterations in fish and other water-breathing animals. The proposed cycle is initiated by a reversal of the function of some inhibitory GABA(A) receptors in the direction of neural excitation and then amplified by adjustments in gene expression aimed at suppressing the excitation but in reality increasing it. In addition, the increased metabolic production of CO2 by overexcited neurons will feed into the cycle by elevating intracellular bicarbonate levels that will lead to increased excitatory ion fluxes through GABA(A) receptors. We also discuss the possibility that an initiation of a vicious cycle could be one of the several factors underlying the differences in neural sensitivity to elevated CO2 displayed by fishes

Novel polymorphic microsatellite markers developed for a common reef sponge, Stylissa carteri

© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Biodiversity 43 (2013): 237-241, doi:10.1007/s12526-013-0151-x.Despite the ubiquitous role sponges play in reef ecosystem dynamics, little is known about population-level connectivity in these organisms. The general field of population genetics in sponges remains in its infancy. To date, microsatellite markers have only been developed for few sponge species and no sponge population genetics studies using microsatellites have been conducted in the Red Sea. Here, with the use of next-generation sequencing, we characterize 12 novel polymorphic loci for the common reef sponge, Stylissa carteri. The number of alleles per loci ranged between three and eight. Observed heterozygosity frequencies (Ho) ranged from 0.125 to 0.870, whereas expected (He) heterozygosity frequencies ranged from 0.119 to 0.812. Only one locus showed consistent deviations from Hardy-Weinberg equilibrium (HWE) in both populations and two loci consistently showed the possible presence of null alleles. No significant linkage disequilibrium was detected for any pairs of loci. These microsatellites will be of use for numerous ecological studies focused on this common and abundant sponge.This work was funded by the King Abdullah University of Science and Technology

Molecular Response of the Brain to Cross-Generational Warming in a Coral Reef Fish

Ocean warming is a threat to marine biodiversity, as it can push marine species beyond their physiological limits. Detrimental effects can occur when marine poikilotherms are exposed to conditions beyond their thermal optima. However, acclamatory mechanisms, such as plasticity, may enable compensation of detrimental effects if warming is experienced during development or across generations. Studies evaluating the molecular responses of fishes to warming have mostly focused on liver, muscle, and gonads, and little is known about the effects on other vital organs, including the brain. This study evaluated the transcriptional program of the brain in the coral reef fish Acanthochromis polyacanthus, exposed to two different warming scenarios: +1.5°C and +3.0°C, across successive generations. Fish were exposed to these conditions in both developmental (F1 and F2) and transgenerational settings (F2 only), as well as a treatment with step-wise warming between generations. The largest differences in gene expression were between individuals of the first and second generation, a pattern that was corroborated by pairwise comparisons between Control F1 and Control F2 (7,500 DEGs) fish. This large difference could be associated with parental effects, as parents of the F1 generation were collected from the wild, whereas parents of the F2 generation were reared in captivity. A general response to warming was observed at both temperatures and in developmental and transgenerational treatments included protein folding, oxygen transport (i.e., myoglobin), apoptosis and cell death, modification of cellular structure, mitochondrial activity, immunity and changes in circadian regulation. Treatments at the highest temperature showed a reduction in synaptic activity and neurotransmission, which matches previous behavioral observations in coral reef fishes. The Transgenerational +3.0°C treatment showed significant activation of the gene pls3, which is known for the development of neuro-muscular junctions under heat-stress. F2 samples exposed to step-wise warming showed an intermediate response, with few differentially expressed genes compared to developmental and transgenerational groups (except for Transgenerational +1.5°C). In combination with previous studies on liver gene expression, this study indicates that warming produces a molecular signature of stress response in A. polyacanthus that is influenced both by the intensity of warming as well as the duration of exposure

Parents exposed to warming produce offspring lower in weight and condition

The parental environment can alter offspring phenotypes via the transfer of non-genetic information. Parental effects may be viewed as an extension of (within-generation) phenotypic plasticity. Smaller size, poorer physical condition, and skewed sex ratios are common responses of organisms to global warming, yet whether parental effects alleviate, exacerbate, or have no impact on these responses has not been widely tested. Further, the relative non-genetic influence of mothers and fathers and ontogenetic timing of parental exposure to warming on offspring phenotypes is poorly understood. Here, we tested how maternal, paternal, and biparental exposure of a coral reef fish (Acanthochromis polyacanthus) to elevated temperature (+1.5°C) at different ontogenetic stages (development vs reproduction) influences offspring length, weight, condition, and sex. Fish were reared across two generations in present-day and projected ocean warming in a full factorial design. As expected, offspring of parents exposed to present-day control temperature that were reared in warmer water were shorter than their siblings reared in control temperature; however, within-generation plasticity allowed maintenance of weight, resulting in a higher body condition. Parental exposure to warming, irrespective of ontogenetic timing and sex, resulted in decreased weight and condition in all offspring rearing temperatures. By contrast, offspring sex ratios were not strongly influenced by their rearing temperature or that of their parents. Together, our results reveal that phenotypic plasticity may help coral reef fishes maintain performance in a warm ocean within a generation, but could exacerbate the negative effects of warming between generations, regardless of when mothers and fathers are exposed to warming. Alternatively, the multigenerational impact on offspring weight and condition may be a necessary cost to adapt metabolism to increasing temperatures. This research highlights the importance of examining phenotypic plasticity within and between generations across a range of traits to accurately predict how organisms will respond to climate change

Exploring seascape genetics and kinship in the reef sponge Stylissa carteri in the Red Sea

A main goal of population geneticists is to study patterns of gene flow to gain a better understanding of the population structure in a given organism. To date most efforts have been focused on studying gene flow at either broad scales to identify barriers to gene flow and isolation by distance or at fine spatial scales in order to gain inferences regarding reproduction and local dispersal. Few studies have measured connectivity at multiple spatial scales and have utilized novel tools to test the influence of both environment and geography on shaping gene flow in an organism. Here a seascape genetics approach was used to gain insight regarding geographic and ecological barriers to gene flow of a common reef sponge, Stylissa carteri in the Red Sea. Furthermore, a small-scale (<1 km) analysis was also conducted to infer reproductive potential in this organism. At the broad scale, we found that sponge connectivity is not structured by geography alone, but rather, genetic isolation in the southern Red Sea correlates strongly with environmental heterogeneity. At the scale of a 50-m transect, spatial autocorrelation analyses and estimates of full-siblings revealed that there is no deviation from random mating. However, at slightly larger scales (100–200 m) encompassing multiple transects at a given site, a greater proportion of full-siblings was found within sites versus among sites in a given location suggesting that mating and/or dispersal are constrained to some extent at this spatial scale. This study adds to the growing body of literature suggesting that environmental and ecological variables play a major role in the genetic structure of marine invertebrate populations

Exploring seascape genetics and kinship in the reef sponge Stylissa carteri in the Red Sea

International audienc

Impact of lower limb movement on the hemodynamics of femoropopliteal arteries: A computational study

Femoropopliteal arteries (FPAs) are subjected to a wide range of deformations, mainly determined by leg movement. FPAs are often affected by atherosclerotic plaque development, presumably influenced by the biomechanics of surrounding tissues. Although abnormal hemodynamics in FPAs appears to be an important factor in driving plaque development, to date it has been investigated in few studies, in which the leg was modeled in either fixed straight or bent configuration. Hence, the current work investigates the impact of leg movement on FPA hemodynamics. An idealized model of FPA was created to perform moving-boundary computational fluid dynamics analyses. By mimicking hip rotation, knee flexion and complete movement of walking, the hemodynamics was compared between moving- and fixed-boundary models. Moreover, additional features affecting the hemodynamics (e.g. flow-rate curve amplitude, walking speed) were examined. Significant hemodynamic differences were found between the moving- and fixed-boundary models, with the leg movement inducing higher time-averaged wall shear stress (TAWSS) (up to 66%). The flow-rate amplitude and walking period were the most influential parameters (differences in TAWSS up to 68% and 74%, respectively). In conclusion, this numerical approach highlighted the importance of considering leg movement to investigate FPA hemodynamics, and it could be employed in future patient-specific analyses

Draft Genome Sequence of the Antitrypanosomally Active Sponge-Associated Bacterium Actinokineospora sp. Strain EG49

The marine sponge-associated bacterium Actinokineospora sp. strain EG49 produces the antitrypanosomal angucycline-like compound actinosporin A. The draft genome of Actinokineospora sp. EG49 has a size of 7.5 megabases and a GC content of 72.8% and contains 6,629 protein-coding sequences (CDS). antiSMASH predicted 996 genes residing in 36 secondary metabolite gene clusters