Sex-specific maternal programming of corticosteroid-binding globulin by predator odour

Predation is a key organizing force in ecosystems. The threat of predation may act to programme the endocrine hypothalamic–pituitary–adrenal axis during development to prepare offspring for the environment they are likely to encounter. Such effects are typically investigated through the measurement of corticosteroids (Cort). Corticosteroid-binding globulin (CBG) plays a key role in regulating the bioavailability of Cort, with only free unbound Cort being biologically active. We investigated the effects of prenatal predator odour exposure (POE) in mice on offspring CBG and its impact on Cort dynamics before, during and after restraint stress in adulthood. POE males, but not females, had significantly higher serum CBG at baseline and during restraint and lower circulating levels of Free Cort. Restraint stress was associated with reduced liver transcript abundance of SerpinA6 (CBG-encoding gene) only in control males. POE did not affect SerpinA6 promoter DNA methylation. Our results indicate that prenatal exposure to a natural stressor led to increased CBG levels, decreased per cent of Free Cort relative to total and inhibited restraint stress-induced downregulation of CBG transcription. These changes suggest an adaptive response to a high predator risk environment in males but not females that could buffer male offspring from chronic Cort exposure.

Living in mixed species groups promotes predator learning in degraded habitats

Living in mix-species aggregations provides animals with substantive anti-predator, foraging and locomotory advantages while simultaneously exposing them to costs, including increased competition and pathogen exposure. Given each species possess unique morphology, competitive ability, parasite vulnerability and predator defences, we can surmise that each species in mixed groups will experience a unique set of trade-offs. In addition to this unique balance, each species must also contend with anthropogenic changes, a relatively new, and rapidly increasing phenomenon, that adds further complexity to any system. This complex balance of biotic and abiotic factors is on full display in the exceptionally diverse, yet anthropogenically degraded, Great Barrier Reef of Australia. One such example within this intricate ecosystem is the inability of some damselfish to utilize their own chemical alarm cues within degraded habitats, leaving them exposed to increased predation risk. These cues, which are released when the skin is damaged, warn nearby individuals of increased predation risk and act as a crucial associative learning tool. Normally, a single exposure of alarm cues paired with an unknown predator odour facilitates learning of that new odour as dangerous. Here, we show that Ambon damselfish, Pomacentrus amboinensis, a species with impaired alarm responses in degraded habitats, failed to learn a novel predator odour as risky when associated with chemical alarm cues. However, in the same degraded habitats, the same species learned to recognize a novel predator as risky when the predator odour was paired with alarm cues of the closely related, and co-occurring, whitetail damselfish, Pomacentrus chrysurus. The importance of this learning opportunity was underscored in a survival experiment which demonstrated that fish in degraded habitats trained with heterospecific alarm cues, had higher survival than those we tried to train with conspecific alarm cues. From these data, we conclude that redundancy in learning mechanisms among prey guild members may lead to increased stability in rapidly changing environments.

Weak swimming response of a bdelloid rotifer to chemical cues of a native copepod predator

Whether bdelloid rotifers can detect and respond to the chemical cues of predators has not been studied, and research on their behaviour is scarce in general. To test for such response, we observed the behaviour of Philodina megalotrocha rotifers in either control or copepod-conditioned water. We then introduced a mechanical disturbance to test if predator odour sensitises rotifers to subsequent cues. We found intensified swimming in P. megalotrocha exposed to Macrocyclops fuscus-conditioned water, i.e. the larger and more predatory of the tested copepods. Such response may be adaptive, depending on the predominant hunting mode of the predator in the particular habitat.

Parents know best: transgenerational predator recognition through parental effects

In highly biodiverse systems, such as coral reefs, prey species are faced with predatory threats from numerous species. Recognition of predators can be innate, or learned, and can help increase the chance of survival. Research suggests that parental exposure to increased predatory threats can affect the development, behaviour, and ultimately, success of their offspring. Breeding pairs of damselfish (Acanthochromis polyacanthus) were subjected to one of three olfactory and visual treatments (predator, herbivore, or control), and their developing embryos were subsequently exposed to five different chemosensory cues. Offspring of parents assigned to the predator treatment exhibited a mean increase in heart rate two times greater than that of offspring from parents in herbivore or control treatments. This increased reaction to a parentally known predator odour suggests that predator-treated parents passed down relevant threat information to their offspring, via parental effects. This is the first time transgenerational recognition of a specific predator has been confirmed in any species. This phenomenon could influence predator-induced mortality rates and enable populations to adaptively respond to fluctuations in predator composition and environmental changes.

SUN-LB49 Chronic Exposure to Predator Odour Stress Disrupts LH Pulsatility and Delays Puberty While Activation of Amygdala Kisspeptin Advances Puberty

Chronic exposure to predator odour stress disrupts LH pulsatility and delays puberty whileactivation of amygdala kisspeptin advances pubertyDeyana Ivanova MS1, Xiao Feng Li MD/PhD1, Caitlin Mcintyre BS1, and Kevin O’Byrne PhD1; 1Department of Women and Children’s Health, Faculty of Life Science and Medicine, King’sCollege London, UKPost-traumatic stress (PTSD) is associated with altered pubertal timing and predator odourexposure is a classical rodent PTSD model. Kisspeptin neurones in the posterodorsal sub-nucleus of the medial amygdala (MePD) are thought to modulate pubertal timing and anxiety.We test the hypothesis that psychosocial stress, processed by the MePD, is relayed to theGnRH pulse generator to delay puberty. Female mice were exposed to predator odour, 2,4,5-Trimethylthiazole (TMT), for 14 days from postnatal day (pnd) 21 and pubertal onset wasmonitored. Anxiety was tested using the Elevated Plus Maze (EPM), Light/Dark Box (LDB) andsocial interaction (SI). The effect of TMT on luteinizing hormone (LH) pulses was measured,on pnd 26 and 29. Additionally, kisspeptin-cre mice were bilaterally injected with hM3Dq-DREADD AAV in the MePD at pnd 13. From pnd 21, CNO was administered via drinking waterfor 14 days and pubertal onset was monitored. The TMT-mice showed a significant delay offirst estrous (FE; TMT: 38.1 ± 0.5 vs. control: 33.3 ± 0.6 days; p<0.0001; n=10-14) withoutaffecting body weight (BW; p=0.9; n=10-14). TMT-mice spent less time exploring the openarm of the EPM (TMT: 13 ± 3 vs. control: 32 ± 5 secs; p<0.05; n=10-14) and in the lightcompartment of the LDB (TMT: 117 ± 12 vs. control: 162 ± 15 secs; p<0.05; n=10-14), whileengaging less in SI (TMT: 26.8 ± 2.8 vs. control: 47.7 ± 8.8 secs; p<0.05; n=10-14) during TMT-exposure compared to controls. The TMT group exhibited a reduction in LH pulse frequencyon pnd 26 (TMT: 0.2 ± 0.2 vs. control: 1.7 ± 0.4 pulses/2 h; p<0.05; n=6-9) and 29 (TMT: 0.6 ±0.2 vs. control: 2.6 ± 0.4 pulses/2 h; p<0.001; n=6-9). DREADD activation of kisspeptinneurones in the MePD advances FE (DREADD: 30 ± 1 vs. control 34.67 ± 0.82 days; p<0.05;n=6) without affecting BW (p=0.9; n=6). Predator odour stress reduces GnRH pulse generatorfrequency, delays puberty and enhances anxiety-like behaviour, while selective chemogeneticactivation of kisspeptin neurones in the MePD advances puberty in female mice.

Mice lacking paternal expression of imprinted Grb10 are risk-takers

ABSTRACTThe imprinted genes Grb10 and Nesp influence impulsive behavior on a delay discounting task in an opposite manner. A recently developed theory suggests that this pattern of behavior may be representative of predicted effects of imprinted genes on tolerance to risk. Here we examine whether mice lacking paternal expression of Grb10 show abnormal behavior across a number of measures indicative of risk-taking. Although Grb10+/p mice show no difference from wild type littermates in their willingness to explore a novel environment, their behavior on an explicit test of risk-taking, namely the Predator Odour Risk-Taking task, is indicative of an increased willingness to take risks. Follow-up tests suggest that this risk-taking is not simply due to a general decrease in fear, or a general increase in motivation for a food reward, but reflects a change in the trade-off between cost and reward. These data, coupled with previous work on the impulsive behaviour of Grb10+/p mice in the delayed reinforcement task, and taken together with our work on mice lacking maternal Nesp, suggest that maternally and paternally expressed imprinted genes oppositely influence risk-taking behaviour as predicted.

Simulating more realistic predation threat using attack playbacks

Use of virtual proxies of live animals are rapidly gaining ground in studies of animal behaviour. Such proxies help to reduce the number of live experimental animals needed to stimulate the behaviour of experimental individuals and to increase standardisation. However, using too simplistic proxies may fail to induce a desired effect and/or lead to quick habituation. For instance, in a predation context, prey often employ multimodal cues to detect predators or use specific aspects of predator behaviour to assess threat. In a live interaction, predator and prey often show behaviours directed towards each other, which are absent in virtual proxies. Here we compared the effectiveness of chemical and visual predator cues in the cooperatively breeding cichlid Neolamprologus pulcher, a species in which predation pressure has been the evolutionary driver of its sociality. We created playbacks of predators simulating an attack and tested their effectiveness in comparison to a playback showing regular activity and to a live predator. We further compared the effectiveness of predator odour and conspecific skin extracts on behaviours directed towards a predator playback. Regular playbacks of calmly swimming predators were less effective than live predators in stimulating a focal individual’s aggression and attention. However, playbacks mimicking an attacking predator induced responses much like a live predator. Chemical cues did not affect predator directed behaviour.

Coral degradation alters predator odour signatures and influences prey learning and survival

Habitat degradation is a key factor leading to the global loss of biodiversity. This problem is particularly acute in coral reef ecosystems. We investigated whether recognition of predator odours by damselfish was influenced by coral degradation and whether these changes altered survival in the wild. We taught whitespot damselfish to recognize the odour of a predator in the presence of live/healthy coral or dead/degraded coral. Fish were tested for a response to predator odours in environments that matched their conditioning environment or in environments that were mismatched. Next, we taught blue damselfish to recognize the odour of three common reef predators in live and degraded coral environments and then stocked them onto live or degraded patch reefs, where we monitored their subsequent response to predator odour along with their survival. Damselfish learned to recognize predator odours in both coral environments, but the intensity of their antipredator response was much greater when the conditioning and test environments matched. Fish released on degraded coral had about 50% higher survival if they had been trained in the presence of degraded coral rather than live coral. Altering the intensity of antipredator responses could have rather profound consequences on population growth.

Does juvenile Baltic sturgeon (Acipenser oxyrinchus) smell the enemy?

SUMMARYAtlantic sturgeon (Acipenser oxyrinchus), also known as Baltic sturgeon, is considered extinct in German waters. Fish-rearing for conservation purposes still relies on classical hatchery technology producing fish not well suited for facing life in the wild, lacking behavioural skills such as foraging or anti-predation. Predation is hence a major source of mortality in newly stocked individuals. The aim of this study was to evaluate if naïve Baltic sturgeon juveniles were able to smell and recognize a common predator, sander (Sander lucioperca). Over a period of 30 days, three tanks from each group of Baltic sturgeon were attached to a rearing tank with sander (sander unit) and, as a control, carp (carp unit). Morphology of the dorsal scutes, distribution within the tank, stress (glucose, lactate and cortisol) and gene expression of brain plasticity and cognition were studied in comparison to the control group (carp unit). No significant differences were observed in any of the parameters measured. Thus, we conclude that naïve Baltic sturgeon is not able to innately recognize potential predators and future studies should focus on implementing predator odour together with chemical alarm substances.