Neural encoding of perceived patch value during competitive and hazardous virtual foraging

Natural observations suggest that in safe environments, organisms avoid competition to maximize gain, while in hazardous environments the most effective survival strategy is to congregate with competition to reduce the likelihood of predatory attack. We probed the extent to which survival decisions in humans follow these patterns, and examined the factors that determined individual-level decision-making. In a virtual foraging task containing changing levels of competition in safe and hazardous patches with virtual predators, we demonstrate that human participants inversely select competition avoidant and risk diluting strategies depending on perceived patch value (PPV), a computation dependent on reward, threat, and competition. We formulate a mathematically grounded quantification of PPV in social foraging environments and show using multivariate fMRI analyses that PPV is encoded by mid-cingulate cortex (MCC) and ventromedial prefrontal cortices (vMPFC), regions that integrate action and value signals. Together, these results suggest humans utilize and integrate multidimensional information to adaptively select patches highest in PPV, and that MCC and vMPFC play a role in adapting to both competitive and predatory threats in a virtual foraging setting.

GABAergic basal forebrain projections to the periaqueductal gray promote food consumption, reward and predation

Behaviors central to the procurement and consumption of food are among those most fundamental to survival, but their inappropriate expression can lead to overeating and obesity. Nevertheless, we have a poor understanding of circuits that promote feeding independent of physiological demand. Here we demonstrate that activation of basal forebrain (BF) GABAergic neurons results in consumption of food as well as non-food items in well-fed mice, and performance of fictive eating in the absence of ingestible materials. In addition, stimulation of these cells disrupts defensive threat responses and elicits reward-like motivational effects. Finally, BF GABAergic activity triggers skilled predatory attack of live prey and prey-like objects, but not social targets. These effects were entirely recapitulated by selective stimulation of BF GABAergic projections to the periacqueductual gray (PAG). Our results outline a potent circuit mechanism for increased feeding through recruitment of distinct but synergistic behaviors, and add to growing evidence that PAG is an important integrator of feeding-related activity.

Growth, survivorship, and predator avoidance capability of larval shortnose sturgeon (Acipenser brevirostrum) in response to delayed feeding

Larval shortnose sturgeon, reared at 17°C, were subjected to delayed feeding treatments of 0, 5, 10, 15, 18, and 23 days post-yolk absorption to examine effects of food deprivation on growth, survival, swimming activity, and escape capabilities. Starvation affected growth and survival but despite degree of starvation, larvae were able to resume growth and experience high survivorship following feeding. Specific growth rate based on larval dry weight for the period directly following first feeding was highest for the day 15 and 18 delayed feeding treatments. There were no differences in survival between the 0 and 5 day treatments, however survival was reduced to 71.2%, 45.4%, and 28.8% for 10, 15, and 18 day delayed feeding treatments, respectively. Shortnose sturgeon had a point-of-no-return (PNR; 55.7% initiated feeding) at ~19 days (or 42 days post-fertilization) following the full absorption of yolk. Mean percent swimming activity and swimming speeds showed an interaction between delayed feeding treatment and larval age, such that no differences were detected at 1 and 6 days post-yolk absorption, while these swimming behaviors generally increased or spiked as feeding was delayed for 10, 15, and 18 days post-yolk absorption. At 23 days post-yolk absorption, only swimming speed increased for larvae that were denied food for 18 days. While there was an interaction between delayed feeding treatments and age for proportion of larvae exhibiting an escape response, generally, larvae from all feeding treatments exhibited a positive escape response. There were also interactions between delayed feeding treatments and age post-yolk absorption for mean and maximum escape speeds, such that less aggressive escape responses were typically detected the longer larvae were denied food. Our research suggests that larval shortnose sturgeon increase physical activity during periods of starvation to find a food patch while remaining vigilant but maybe not as capable to defend against a predatory attack as fed individuals.

The lateral periaqeductal gray and its role in controlling the opposite behavioral choices of predatory hunting and social defense

Evasion from imminent threats and prey attack are opposite behavioral choices critical to survival. Curiously, the lateral periaqueductal gray (LPAG) has been implicated in driving both responses. The LPAG responds to social threats and prey hunting while also drives predatory attacks and active defense. However, the LPAG neural mechanisms mediating these behaviors remain poorly defined. Here, we investigate how the LPAG mediates the choices of predatory hunting and evasion from a social threat. Pharmacogenetic inhibition in Fos DD-Cre mice of neurons responsive specifically to insect predation (IP) or social defeat (SD) revealed that distinct neuronal populations in the LPAG drive the prey hunting and evasion from social threats. We show that the LPAG provides massive glutamatergic projection to the lateral hypothalamic area (LHA). Optogenetic inhibition of the LPAG-LHA pathway impaired IP but did not alter escape/attack ratio during SD. We also found that pharmacogenetic inhibition of LHAGABA neurons impaired IP, but did not change evasion during SD. The results suggest that the LPAG control over evasion to a social attack may be regarded as a stereotyped response depending probably on glutamatergic descending projections. On the other hand, the LPAG control over predatory behavior involves an ascending glutamatergic pathway to the LHA that likely influences LHAGABA neurons driving predatory attack and prey consumption. The LPAG-LHA path supposedly provides an emotional drive for prey hunting and, of relevance, may conceivably have more widespread control on the motivational drive to seek other appetitive rewards.

DOES APOSEMATIC COLORATION REDUCE PREDATION RISK IN SNAKES? A SHORT PERIOD EXPERIMENT USING PLASTICINE SNAKE MODELS

Aposematism in an anti-predation mechanism that occurs when animals exhibit conspicuous signals, which are often of a contrasting color patterns, to alert potential predators of their unpalatability or toxicity. This study aims to test (in a short period) the effectiveness of aposematic coloration by comparing the predatory attack upon snakes models with and without an alert coloration on the body. To simulate snakes, we made 80 greenish plasticine snake models. Half of the models had a red strip on the dorsal part of the body, imitating an aposematic coloration. The other half of the models had only a greenish tint. The models were exposed to predators for 12 hours in an area with countryside vegetation.. Among the 20 models showing signs of predation, 65% were purely greenish models and 35% were models with red coloration on the back. Attaks at extremities (head and tail) were meaningly more frequent on models with red coloration. Our results suggest the efficiency of red coloration as a warning sign and anti-predation mechanism, since the models with red coloration, imitating aposematic preys, were less preyed and were attacked preferentially at the extremities, which suggests caution by the predator.

A molecular filter for the cnidarian stinging response

All animals detect and integrate diverse environmental signals to mediate behavior. Cnidarians, including jellyfish and sea anemones, both detect and capture prey using stinging cells called nematocytes which fire a venom-covered barb via an unknown triggering mechanism. Here, we show that nematocytes from Nematostella vectensis use a specialized voltage-gated calcium channel (nCaV) to distinguish salient sensory cues and control the explosive discharge response. Adaptations in nCaV confer unusually sensitive, voltage-dependent inactivation to inhibit responses to non-prey signals, such as mechanical water turbulence. Prey-derived chemosensory signals are synaptically transmitted to acutely relieve nCaV inactivation, enabling mechanosensitive-triggered predatory attack. These findings reveal a molecular basis for the cnidarian stinging response and highlight general principles by which single proteins integrate diverse signals to elicit discrete animal behaviors.

Testing the differential cost assumption of the handicap hypothesis with a tropical jumping spider

The handicap hypothesis predicts that more elaborate males attract more predators, but are also better able to escape attacks. Thus, a unit increase in trait elaboration has a lower cost for a high-quality male (i.e., differential cost). Although widely accepted, the handicap hypothesis has seldom been appropriately tested, especially concerning the differential cost assumption. Here, we tested this assumption using the jumping spider Hasarius adansoni. The courtship display of male H. adansoni involves bright white patches that contrast with their dark-coloured body. In experimental trials, we measured male escape capacity following a simulated predatory attack. Measurements of escape capacity were correlated to the size of white patches. Contrary to expectations, spiders with larger white patches did not exhibit better escape capacity. We conclude that this trait does not function as a handicap. It is possible that other sexual selection processes are at work.

A molecular filter for the cnidarian stinging response

All animals detect and integrate diverse environmental signals to mediate behavior. Cnidarians, including jellyfish and sea anemones, both detect and capture prey using stinging cells called nematocytes which fire a venom-covered barb via an unknown triggering mechanism. Here, we show that nematocytes from Nematostella vectensis use a specialized voltage-gated calcium channel (nCav) to distinguish salient sensory cues and control the explosive discharge response. Adaptations in nCav confer unusually-sensitive, voltage-dependent inactivation to inhibit responses to non-prey signals, such as mechanical water turbulence. Prey-derived chemosensory signals are synaptically transmitted to acutely relieve nCav inactivation, enabling mechanosensitive-triggered predatory attack. These findings reveal a molecular basis for the cnidarian stinging response and highlight general principles by which single proteins integrate diverse signals to elicit discrete animal behaviors.