Predator Stress Research Articles

Transgenerational exposure to marine heatwaves ameliorates the lethal effect on tropical copepods regardless of predation stress.

Marine heatwaves (MHWs) are emerging as a severe stressor in marine ecosystems. Extreme warm sea surface temperatures during MHWs often exceed the optimal thermal range for more than one generation of tropical coastal zooplankton. However, it is relatively unknown whether transgenerational plasticity (TGP) to MHWs may shape the offspring's fitness, particularly in an ecologically relevant context with biotic interactions such as predation stress. We addressed these novel research questions by determining the survival, reproductive success, and grazing rate of the copepod Pseudodiaptomus incisus exposed to MHW and fish predator cues (FPC) for two generations (F1 and F2). The experiment was designed in a full orthogonal manner with 4 treatments in F1 and 16 treatments in F2 generation. In both generations, MHW reduced P. incisus survival, reproductive parameters, and grazing by 10%–62% in MHW, but these parameters increased by 2%–15% with exposure to FPC, particularly at control temperature. F2 reproductive success and grazing rate as indicated by cumulative fecal pellets were reduced by 20%–30% in F1‐MHW, but increased by ~2% in F1‐FPC. Strikingly, MHW exposure reduced 17%–18% survival, but transgenerational exposure to MHWs fully ameliorated its lethal effect and this transgenerational effect was independent of FPC. Increased survival came with a cost of reduced reproductive success, constrained by reduced grazing. The rapid transgenerational MHW acclimation and its associated costs are likely widespread and crucial mechanisms underlying the resilience of coastal tropical zooplankton to MHWs in tropical coastal marine ecosystems.

Level-dependent effects of predation stress on prey development, lifespan and reproduction in mites

In predator–prey interactions, non-consumptive effects of predators have been less studied than consumptive effects. However, non-consumptive effects may have significant influences on prey and can change different aspects of their life history such as development, reproduction and lifespan. The odour and other cues associated with a predator, without direct contact, could induce stress in prey, leading to phenotypic changes in life history traits. In this study, we investigate how mild and strong predator-induced stress could affect prey life history. The prey (Tyrophagus putrescentiae) was exposed, from hatching to death, to three different levels of predation stress from its predator (Neoseiulus cucumeris) (1, 3 or 5 predator adults in an adjacent cage separated by a mesh screen). Compared with the control, both males and females under predator-induced stress had longer developmental time and shorter lifespan when the level of predation stress increased, showing significant level-dependence. In addition, females had reduced fecundity under predation stress. Sex-specific response to predation stress was observed under a low level of predation stress: females had greater reduction in lifespan than males. Furthermore, the reduction in female lifespan was due more from the decrease in the post-oviposition period than the decrease in the oviposition period. Future studies applying even milder levels of predation press, such as exposure of prey to predator cues only during part of the prey lifespan, may provide additional insights.

Short-term responses of Rana arvalis tadpoles to pH and predator stress: adaptive divergence in behavioural and physiological plasticity?

Environmental stress is a major driver of ecological and evolutionary processes in nature. To cope with stress, organisms can adjust through phenotypic plasticity and/or adapt through genetic change. Here, we compared short-term behavioural (activity) and physiological (corticosterone levels, CORT) responses of Rana arvalis tadpoles from two divergent populations (acid origin, AOP, versus neutral origin, NOP) to acid and predator stress. Tadpoles were initially reared in benign conditions at pH 7 and then exposed to a combination of two pH (acid versus neutral) and two predator cue (predator cue versus no predator cue) treatments. We assessed behavioural activity within the first 15 min, and tissue CORT within 8 and 24 h of stress exposure. Both AOP and NOP tadpoles reduced their activity in acidic pH, but the response to the predator cue differed between the populations: AOP tadpoles increased whereas NOP tadpoles decreased their activity. The AOP and NOP tadpoles differed also in their CORT responses, with AOP being more responsive (CORT levels of NOP tadpoles did not differ statistically across treatments). After 8 h exposure, AOP tadpoles had elevated CORT levels in the acid-predator cue treatment and after 24 h exposure they had elevated CORT levels in all three stress treatments (relative to the benign neutral–no-cue treatment). These results suggest that adaptation to environmental acidification in R. arvalis is mediated, in part, via behavioural and hormonal plasticity.

Intersexual differences in the number of genes differentially expressed in wild mammals in response to predation risk

Predation is a psychological stressor in prey animals. Besides direct killing and consumption by predators, the perception of predation risk indirectly influence prey population behavior, dynamics and physiology. Few studies identified the transcriptomic response associated with predator presence/abundance in natural populations and uncontrolled settings. However, to our knowledge, intersexual differences in the number of genes whose expression change in response to high predation risk have not been previously reported in wild mammals. Here, by using publicly available gene expression data in wild yellow-bellied marmots (Marmota flaviventer), we found that the number of differentially expressed genes in response to predator stress is higher in female marmots (n = 516) than males (n = 387). Only a small percentage of these differentially expressed genes (n = 36) are shared between the sexes, and that the most of the differentially expressed genes are expressed in a sex-specific manner in response to predation stress. Overall, our results provide new insight into sex-specific variation in gene expression changes in wild mammals under high predation risk.

Phenotypically Determined Liver Dysfunction in a Wistar Rat Model of Post-Traumatic Stress Disorder.

The extraordinary situation of the 2019–2022 pandemic caused a dramatic jump in the incidence of post-traumatic stress disorder (PTSD). PTSD is currently regarded not only as a neuropsychiatric disorder, but also as a comorbidity accompanied by cardiovascular diseases, circulatory disorders, liver dysfunction, etc. The relationship between behavioral disorders and the degree of morphofunctional changes in the liver remains obscure. In this study, PTSD was modeled in sexually mature male Wistar rats using predatory stress induced by a prey’s fear for a predator. Testing in an elevated plus maze allowed the rat population to be divided into animals with low-anxiety (LAP) and high-anxiety (HAP) phenotypes. It was found that morphofunctional analysis of the liver, in contrast to its biochemical profiling, provides a clearer evidence that predatory stress induces liver dysfunction in rats of both phenotypes. This may indicate a decrease in the range of compensatory adaptive reactions in stressed animals. However, in HAP rats, the level of morphofunctional abnormalities in the mechanisms responsible for carbohydrate-fat, water-electrolyte and protein metabolism in the liver testified the prenosological state of the organ, while further functional loading and resulting tension of the regulatory systems could lead to homeostatic downregulation. Meanwhile, the liver of LAP animals was only characterized by insignificant diffuse changes. Thus, we demonstrate here a link between behavioral changes and the degree of morphofunctional transformation of the liver.

Marine gastropods at higher trophic level show stronger tolerance to ocean acidification

Climate change and anthropogenic activities are producing a range of new selection pressures, both abiotic and biotic, on marine organisms. Although it is known that climate change can differentially affect fitness‐related traits at different trophic levels of the food web, it is not clear if different trophic levels will respond via phenotypic plasticity in the form of maintenance of phenotypes in the face of abiotic and biotic environmental stress similarly. To answer this question, we combined a mesocosm experiment (120 days) using a food web comprising three gastropod species from two trophic levels (grazers and meso‐predators) and a meta‐analysis including 38 studies to address whether different trophic levels exhibit similar phenotypic responses to abiotic and biotic variables. Abiotic (ocean acidification) and biotic (predation) stress significantly influenced body mass, shell mass, shell thickness and shell strength in both grazers and meso‐predators in the mesocosm experiment, with the magnitude of OA effects greater on the meso‐predator than the grazers; a result supported by the meta‐analysis. In contrast, both mesocosm experiment and meta‐analysis found that predation risk induced stronger responses in shell morphology for grazers compared to meso‐predators. Together, our findings indicate that higher trophic level species are better able to maintain aspects of their phenotype under OA, suggesting that they may show greater tolerance to climate change effects in general, while lower trophic levels express higher levels of plastic inducible defences to maintain function when under threat of predation. By using marine snails as a model, our study provides new knowledge for understanding how changing environmental conditions may alter biological interactions, and increases our understanding of how climate change may affect ecological communities in which gastropods play a key role.

The anxiogenic effects of adolescent psychological stress in male and female mice

Adolescence is a period of transition during which there is extensive development of the brain and the hypothalamic-pituitary-adrenal axis. However, the term adolescence is broad and covers a number of important developmental periods ranging from pre-pubescence to sexual maturity. Using a predator stress model, we investigated the effects of chronic psychological stress on anxiety-like, depression-like, and social behaviours in male and female mice during early adolescence, when mice are pre-pubertal, and late adolescence, when mice are sexually mature. All stressed mice showed hyperactivity and increased anxiety-like behaviours. The anxiogenic effects were generally more pronounced in mice exposed to late, rather than early adolescent stress, but were clearly evident when stress was experienced at either timepoint. Risk assessment behaviours were also affected by the stress treatments, but the direction of these changes were sometimes sex- and age-specific. Surprisingly, mice stressed during adolescence showed no depressive-like behaviours as adults. This study provides evidence that adolescent psychological stress has pronounced long-term anxiogenic effects but that the precise behavioural phenotype differs based on sex and the sub-stage of adolescence during which the individual is exposed.

Differentiating metabolomic responses of amphibians to multiple stressors

One of the biggest challenges in ecological risk assessment is determining the impact of multiple stressors on individual organisms and populations in real world scenarios. Frequently, data derived from laboratory studies of single stressors are used to estimate risk parameters and do not adequately address scenarios where other stressors exist. Emerging ‘omic technologies, notably metabolomics, provide an opportunity to address the uncertainties surrounding ecological risk assessment of multiple stressors. The objective of this study was to use metabolomic profiling to investigate the effect of multiple stressors on amphibian metamorphs. We exposed post-metamorphosis (180 days) southern leopard frogs (Lithobates sphenocephala) to the insecticide carbaryl (480 μg/L), predation stress, and a combined pesticide and predation stress treatment. Corticosterone analysis revealed mild support for an induction in response to predation stress alone but strongly suggests that carbaryl exposure, alone or in combination with predation cues, can significantly elevate this known biomarker in amphibians. Metabolomics analysis accurately classed, based on relative nearness, carbaryl and predation induced changes in the hepatic metabolome and biochemical fluxes appear to be associated with a similar biological response. Support vector machine analysis with recursive feature elimination of the acquired metabolomic spectra demonstrated 85–96% classification accuracy among control and all treatment groups when using the top 75 ranked retention time bins. Biochemical fluxes observed in the groups exposed to carbaryl, predation, and the combined treatment include amino acids, sugar derivatives, and purine nucleotides. Ultimately, this methodology could be used to interpret short-term toxicity assays and the presence of environmental stressors to overall metabolomic effects in non-target organisms.

Sensitivity and Resilience to Predator Stress-Enhanced Ethanol Drinking Is Associated With Sex-Dependent Differences in Stress-Regulating Systems.

Stress can increase ethanol drinking, and evidence confirms an association between post-traumatic stress disorder (PTSD) and the development of alcohol use disorder (AUD). Exposure to predator odor is considered a traumatic stressor, and predator stress (PS) has been used extensively as an animal model of PTSD. Our prior work determined that repeated exposure to intermittent PS significantly increased anxiety-related behavior, corticosterone levels, and neuronal activation in the hippocampus and prefrontal cortex in naïve male and female C57BL/6J mice. Intermittent PS exposure also increased subsequent ethanol drinking in a subgroup of animals, with heterogeneity of responses as seen with comorbid PTSD and AUD. The present studies built upon this prior work and began to characterize “sensitivity” and “resilience” to PS-enhanced drinking. Ethanol drinking was measured during baseline, intermittent PS exposure, and post-stress; mice were euthanized after 24-h abstinence. Calculation of median and interquartile ranges identified “sensitive” (>20% increase in drinking over baseline) and “resilient” (no change or decrease in drinking from baseline) subgroups. Intermittent PS significantly increased subsequent ethanol intake in 24% of male (↑60%) and in 20% of female (↑71%) C57BL/6J mice in the “sensitive” subgroup. Plasma corticosterone levels were increased significantly after PS in both sexes, but levels were lower in the “sensitive” vs. “resilient” subgroups. In representative mice from “sensitive” and “resilient” subgroups, prefrontal cortex and hippocampus were analyzed by Western Blotting for levels of corticotropin releasing factor (CRF) receptor 1, CRF receptor 2, CRF binding protein, and glucocorticoid receptor, vs. separate naïve age-matched mice. In prefrontal cortex, CRF receptor 1, CRF receptor 2, CRF binding protein, and glucocorticoid receptor levels were significantly higher in “sensitive” vs. naïve and “resilient” mice only in females. In hippocampus, CRF receptor 1, CRF receptor 2 and glucocorticoid receptor levels were significantly lower in “resilient” vs. naïve and “sensitive” mice across both sexes. These results indicate that sex strongly influences the effects of ethanol drinking and stress on proteins regulating stress and anxiety responses. They further suggest that targeting the CRF system and glucocorticoid receptors in AUD needs to consider the comorbidity of PTSD with AUD and sex of treated individuals.

Food quality, security, and thermal refuge influence the use of microsites and patches by pygmy rabbits (Brachylagus idahoensis) across landscapes and seasons

How intensely animals use habitat features depends on their functional properties (i.e., how the feature influences fitness) and the spatial and temporal scale considered. For herbivores, habitat use is expected to reflect the competing risks of starvation, predation, and thermal stress, but the relative influence of each functional property is expected to vary in space and time. We examined how a dietary and habitat specialist, the pygmy rabbit (Brachylagus idahoensis), used these functional properties of its sagebrush habitat—food quality, security, and thermal refuge—at two hierarchical spatial scales (microsite and patch) across two seasons (winter and summer). At the microsite and patch scales, we determined which plant functional traits predicted the number of bites (i.e., foraging) by pygmy rabbits and the number of their fecal pellets (i.e., general habitat use). Pygmy rabbits used microsites and patches more intensely that had higher crude protein and aerial concealment cover and were closer to burrows. Food quality was more influential when rabbits used microsites within patches. Security was more influential in winter than summer, and more at Cedar Gulch than Camas. However, the influence of functional properties depended on phytochemical and structural properties of sagebrush and was not spatiotemporally consistent. These results show function‐dependent habitat use that varied according to specific activities by a central‐place browsing herbivore. Making spatially explicit predictions of the relative value of habitat features that influence different types of habitat use (i.e., foraging, hiding, and thermoregulating) will improve how we predict patterns of habitat use by herbivores and how we monitor and manage functional traits within habitats for wildlife.

The Link between Activities of Hepatic 11beta-Hydroxysteroid Dehydrogenase-1 and Monoamine Oxidase-A in the Brain Following Repeated Predator Stress: Focus on Heightened Anxiety.

We investigated the presence of a molecular pathway from hepatic 11-βHSD-1 to brain MAO-A in the dynamics of plasma corticosterone involvement in anxiety development. During 14 days following repeated exposure of rats to predator scent stress for 10 days, the following variables were measured: hepatic 11-βHSD-1 and brain MAO-A activities, brain norepinephrine, plasma corticosterone concentrations, and anxiety, as reflected by performance on an elevated plus maze. Anxiety briefly decreased and then increased after stress exposure. This behavioral response correlated inversely with plasma corticosterone and with brain MAO-A activity. A mathematical model described the dynamics of the biochemical variables and predicted the factor(s) responsible for the development and dynamics of anxiety. In the model, hepatic 11-βHSD-1 was considered a key factor in defining the dynamics of plasma corticosterone. In turn, plasma corticosterone and oxidation of brain ketodienes and conjugated trienes determined the dynamics of brain MAO-A activity, and MAO-A activity determined the dynamics of brain norepinephrine. Finally, plasma corticosterone was modeled as the determinant of anxiety. Solution of the model equations demonstrated that plasma corticosterone is mainly determined by the activity of hepatic 11-βHSD-1 and, most importantly, that corticosterone plays a critical role in the dynamics of anxiety following repeated stress.

P389. NF-ΚB and HMGB1 Differentially Mediate Effects of Acute Predator Stress on Anhedonia and Behavioral Despair

We previously have shown that acute predator stress activates NF-κB and HMGB1 inflammatory markers in brain regions relevant for stress response and depression, specifically in nucleus accumbens (NA) and anterior cingulate cortex (ACC). In this study, we aimed to determine whether pharmacological inhibition of NF-κB and HMGB1 reverses anhedonia and behavioral despair in mice.

Differences in Corticosterone Release Rates of Larval Spring Salamanders (Gyrinophilus porphyriticus) in Response to Native Fish Presence.

Simple SummaryIn amphibians, glucocorticoid hormones play a key role in the response to predation stress. Predators can directly affect prey via injury and death, but they can also have indirect effects due to the activity of glucocorticoids. The regulation of glucocorticoids can differ between populations that have co-evolved with predators and those that have not. We measured glucocorticoids at baseline and in response to a novel stressor in free-living larval salamanders that either live with or without fish predators naturally. We found that salamanders living with fish predators had lower measures of glucocorticoids than those without fish predators. Our study indicates that predator presence alters glucocorticoid regulation, which may allow species to better cope with native and introduced predators.Invasive fish predators are an important factor causing amphibian declines and may have direct and indirect effects on amphibian survival. For example, early non-lethal exposure to these stressors may reduce survival in later life stages, especially in biphasic species. In amphibians, the glucocorticoid hormone corticosterone is released by the hypothalamo–pituitary–interrenal axis (HPI), as an adaptive physiological response to environmental stressors. The corticosterone response (baseline and response to acute stressors) is highly flexible and context dependent, and this variation can allow individuals to alter their phenotype and behavior with environmental changes, ultimately increasing survival. We sampled larvae of the spring salamander (Gyrinophilus porphyriticus) from two streams that each contained predatory brook trout (Slavelinus fontinalis) in the lower reaches and no predatory brook trout in the upper reaches. We measured baseline and stress-induced corticosterone release rates of larvae from the lower and upper reaches using a non-invasive water-borne hormone assay. We hypothesized that corticosterone release rates would differ between larvae from fish-present reaches and larvae from fish-free reaches. We found that baseline and stressor-induced corticosterone release rates were downregulated in larvae from reaches with fish predators. These results indicate that individuals from reaches with predatory trout are responding to fish predators by downregulating corticosterone while maintaining an active HPI axis. This may allow larvae more time to grow before metamorphosing, while also allowing them to physiologically respond to novel stressors. However, prolonged downregulation of corticosterone release rates can impact growth in post-metamorphic individuals.

Predation Stress Causes Excessive Aggression in Female Mice with Partial Genetic Inactivation of Tryptophan Hydroxylase-2: Evidence for Altered Myelination-Related Processes.

The interaction between brain serotonin (5-HT) deficiency and environmental adversity may predispose females to excessive aggression. Specifically, complete inactivation of the gene encoding tryptophan hydroxylase-2 (Tph2) results in the absence of neuronal 5-HT synthesis and excessive aggressiveness in both male and female null mutant (Tph2−/−) mice. In heterozygous male mice (Tph2+/−), there is a moderate reduction in brain 5-HT levels, and when they are exposed to stress, they exhibit increased aggression. Here, we exposed female Tph2+/− mice to a five-day rat predation stress paradigm and assessed their emotionality and social interaction/aggression-like behaviors. Tph2+/− females exhibited excessive aggression and increased dominant behavior. Stressed mutants displayed altered gene expression of the 5-HT receptors Htr1a and Htr2a, glycogen synthase kinase-3 β (GSK-3β), and c-fos as well as myelination-related transcripts in the prefrontal cortex: myelin basic protein (Mbp), proteolipid protein 1 (Plp1), myelin-associated glycoprotein (Mag), and myelin oligodendrocyte glycoprotein (Mog). The expression of the plasticity markers synaptophysin (Syp) and cAMP response element binding protein (Creb), but not AMPA receptor subunit A2 (GluA2), were affected by genotype. Moreover, in a separate experiment, naïve female Tph2+/− mice showed signs of enhanced stress resilience in the modified swim test with repeated swimming sessions. Taken together, the combination of a moderate reduction in brain 5-HT with environmental challenges results in behavioral changes in female mice that resemble the aggression-related behavior and resilience seen in stressed male mutants; additionally, the combination is comparable to the phenotype of null mutants lacking neuronal 5-HT. Changes in myelination-associated processes are suspected to underpin the molecular mechanisms leading to aggressive behavior.

Short Juvenile Stress Has No Long-Lasting Effects on Anxiety-Like Behavior, Object Recognition Memory, or Gross Brain Morphology but Affects Dendritic Spines in the Hippocampus in Male Rats

Purpose: During the juvenile stage, such areas as the hippocampus and corpus callosum (CC) are still immature and sensitive to stress exposure. The present study investigated whether two different types of stressors in the juvenile stage of life have a long-lasting impact on behavior and biological outcomes in adult rats. Methods: Male juvenile rats were exposed to restraint or predator stress on postnatal day 25 (P25) for 3 days. Thirty-two days later (P60-74), behavioral and biological analyses were conducted. The behavioral analysis included measures of anxiety-like behavior and recognition memory. The biological analysis investigated gross cerebral morphology, based on volume analysis of the CC and hippocampus, perirhinal cortex thickness, and dendritic spine density. Results: Neither restraint stress nor predator stress affected anxiety-like behavior or object recognition memory in adulthood. Body weight and adrenal gland weight were unaffected by both types of stress. Overall, volumetric measures of the CC and hippocampus were not significant, with no changes in perirhinal cortex thickness. Spine density in the medial prefrontal cortex also was unaffected, but a decrease in dendritic spine density was found in the hippocampus in response to restraint stress and an increase to predator stress. Conclusion: Short-term and daily restraint and predator stress during the juvenile stage had no long-lasting effects on anxiety-like behavior, object memory, volume of the CC or hippocampus, or perirhinal cortex thickness, but a decrease in dendritic spine density was found in the hippocampus. These findings suggest that different types of stressors have different impacts on microstructures in the brain without affecting behavior or the gross morphology of stress-sensitive brain areas.

The subthalamic corticotropin-releasing hormone neurons mediate adaptive REM-sleep responses to threat

When an animal faces a threatening situation while asleep, rapid arousal is the essential prerequisite for an adequate response. Here, we find that predator stimuli induce immediate arousal from REM sleep compared with NREM sleep. Using invivo neural activity recording and cell-type-specific manipulations, we identify neurons in the medial subthalamic nucleus (mSTN) expressing corticotropin-releasing hormone (CRH) that mediate arousal and defensive responses to acute predator threats received through multiple sensory modalities across REM sleep and wakefulness. We observe involvement of the same neurons in the normal regulation of REM sleep and the adaptive increase in REM sleep induced by sustained predator stress. Projections to the lateral globus pallidus (LGP) are the effector pathway for the threat-coping responses and REM-sleep expression. Together, our findings suggest adaptive REM-sleep responses could be protective against threats and uncover a critical component of the neural circuitry at their basis.

Temporary Retention in Cold Water Reduces Postrelease Behavioral Impairment in Angled Rainbow Trout

AbstractThe effectiveness of catch and release as a conservation practice assumes minimal impacts to released fish. In most cases, angling‐related stressors can be mitigated via changes to angler behavior that reduce fight duration, handling, and air exposure. In some cases, stressors may significantly impact the ability of fish to engage in normal swimming behavior upon release. In these scenarios, it may be beneficial for anglers to assist recovery or retain fish until they are adequately recovered. We investigated the effectiveness of two assisted‐recovery devices at facilitating behavioral recovery in angled Rainbow Trout Oncorhynchus mykiss: (1) retention in a flow box, or (2) retention in a water‐filled cooler. Additionally, we compared the effects of assisted recovery in surface water (24–27°C) or cool water pumped from the hypolimnion (17–19°C). From July to mid‐September 2020, 169 fish were angled from five stocked lakes at Kenauk Nature (Montebello, Quebec). Fish were air exposed for 30 s, for 15 s, or not at all (0 s) and were held in a flow box or a water‐filled cooler for 3 min, while fish in a control group were immediately released. Triaxial acceleration and temperature biologgers were temporarily fixed around the trunk of the fish with Velcro to observe postrelease swimming behavior for 10 min. Rainbow Trout that were held in assisted‐recovery devices regained equilibrium significantly more quickly than those that were immediately released, and fish that were held in 17–19°C water regained equilibrium the most rapidly. In fish that were air exposed for 30 s, individuals that were held in recovery devices exhibited greater swimming activity compared to those that were immediately released. Our study demonstrates that for Rainbow Trout, assisted‐recovery devices can reduce equilibrium impairment, especially when water in the recovery devices is significantly cooler than the relatively warm surface water temperature. Global water temperatures are expected to rise as a result of anthropogenic climate change, and best practices for angling should be adapted to reflect increased thermal stressors for many game fish species. Ensuring that fish are vigorous upon release is imperative for reducing postrelease mortality caused by predation or thermal stress.

Pharmahuasca and DMT Rescue ROS Production and Differentially Expressed Genes Observed after Predator and Psychosocial Stress: Relevance to Human PTSD.

Post-traumatic stress disorder (PTSD) is associated with cognitive deficits, oxidative stress, and inflammation. Animal models have recapitulated features of PTSD, but no comparative RNA sequencing analysis of differentially expressed genes (DEGs) in the brain between PTSD and animal models of traumatic stress has been carried out. We compared DEGs from the prefrontal cortex (PFC) of an established stress model to DEGs from the dorsolateral PFC (dlPFC) of humans. We observed a significant enrichment of rat DEGs in human PTSD and identified 20 overlapping DEGs, of which 17 (85%) are directionally concordant. N,N-dimethyltryptamine (DMT) is a known indirect antioxidant, anti-inflammatory, and neuroprotective compound with antidepressant and plasticity-facilitating effects. We tested the capacity of DMT, the monoamine oxidase inhibitor (MAOI) harmaline, and "pharmahuasca" (DMT + harmaline) to reduce reactive oxygen species (ROS) production and inflammatory gene expression and to modulate neuroplasticity-related gene expression in the model. We administered DMT (2 mg/kg IP), harmaline (1.5 mg/kg IP), pharmahuasca, or vehicle every other day for 5 days, following a 30 day stress regiment. We measured ROS production in the PFC and hippocampus (HC) by electron paramagnetic resonance spectroscopy and sequenced total mRNA in the PFC. We also performed in vitro assays to measure the affinity and efficacy of DMT and harmaline at 5HT2AR compared to 5-HT. DMT and pharmahuasca reduced ROS production in the PFC and HC, while harmaline had mixed effects. Treatments normalized 9, 12, and 14 overlapping DEGs, and pathway analysis implicated that genes were involved in ROS production, inflammation, growth factor signaling, neurotransmission, and neuroplasticity.

Loss of an apex predator in the wild induces physiological and behavioural changes in prey.

Predators can impact prey via predation or risk effects, which can initiate trophic cascades. Given widespread population declines of apex predators, understanding and predicting the associated ecological consequences is a priority. When predation risk is relatively unpredictable or uncontrollable by prey, the loss of predators is hypothesized to release prey from stress; however, there are few tests of this hypothesis in the wild. A well-studied predator-prey system between white sharks (Carcharodon carcharias) and Cape fur seals (Arctocephalus pusillus pusillus) in False Bay, South Africa, has previously demonstrated elevated faecal glucocorticoid metabolite concentrations (fGCMs) in seals exposed to high levels of predation risk from white sharks. A recent decline and disappearance of white sharks from the system has coincided with a pronounced decrease in seal fGCM concentrations. Seals have concurrently been rafting further from shore and over deeper water, a behaviour that would have previously rendered them vulnerable to attack. These results show rapid physiological and behavioural responses by seals to release from predation stress. To our knowledge, this represents the first demonstration in the wild of physiological changes in prey from predator decline, and such responses are likely to increase given the scale and pace of apex predator declines globally.

Molluscan Shell Diversity of Ennore Creek, Chennai, India

Molluscs are the soft bodied invertebrates, which are protected by calcium carbonate shells. The shells are coated mostly with calcium carbonate and protein matrix in a process called bio-mineralization. Apart from playing a major role in the aquatic ecosystem, they are considered to be best bio-indicators of environmental pollution, as their soft tissues, and their shells are known to accumulate the pollutants. The divers patterns and different shell morphologies of the clams, snails and oysters, seem to be influenced by the solar radiation, predator stress and various environmental factors, which seem to regulate the gene expression patterns of the shell formation. In the present study, different molluscan shells were collected and studied for their diverse patterns. They were collected from Ennore, creek of Tamil Nadu, India as it is known to be a lagoon type of ecosystem and plays an important role in maintenance of the aquatic ecosystem surrounding it. The present study showed a diverse shell patterns mostly with reference to clam shells. A few, oyster shells, cerithiid shells and potaminind shells were also observed. A detailed analysis of the shell patterns under the influence of various external environmental cues may be investigated in future.