One of these morphs is not like the others: orange morphs exhibit different escape behavior than other morphs in a color polymorphic lizard

Variation in color morph behavior is an important factor in the maintenance of color polymorphism. Alternative anti-predator behaviors are often associated with morphological traits such as coloration, possibly because predator-mediated viability selection favors certain combinations of anti-predator behavior and color. The Aegean wall lizard, Podarcis erhardii, is color polymorphic and populations can have up to three monochromatic morphs: orange, yellow, and white. We investigated whether escape behaviors differ among coexisting color morphs, and if morph behaviors are repeatable across different populations with the same predator species. Specifically, we assessed color morph flight initiation distance (FID), distance to the nearest refuge (DNR), and distance to chosen refuge (DR) in two populations of Aegean wall lizards from Naxos island. We also analyzed the type of refugia color morphs selected and their re-emergence behavior following a standardized intrusion event. We found that orange morphs have different escape behaviors from white and yellow morphs, and these differences are consistent in both of the populations we sampled. Orange morphs have shorter FIDs, DNRs, and DRs, select different refuge types, and re-emerge less often after an intruder event compared to white and yellow morphs. Observed differences in color morph escape behaviors support the idea that morphs have evolved alternative behavioral strategies that may play a role in population-level morph maintenance and loss.

Focal Laser Stimulation of Fly Nociceptors Activates Distinct Axonal and Dendritic Ca2+ Signals

Drosophila Class IV neurons are polymodal nociceptors that detect noxious mechanical, thermal, optical and chemical stimuli. Escape behaviors in response to attacks by parasitoid wasps are dependent on Class IV cells, whose highly branched dendritic arbors form a fine meshwork that is thought to enable detection of the wasp's needle-like ovipositor barb. To understand how mechanical stimuli trigger cellular responses, we used a focused 405-nm laser to create highly local lesions to probe the precise position needed in evoke responses. By imaging calcium signals in dendrites, axons, and soma in response to stimuli of varying positions, intensities and spatial profiles, we discovered that there are two distinct nociceptive pathways. Direct stimulation to dendrites (the contact pathway) produces calcium responses in axons, dendrites and the cell body whereas stimulation adjacent to the dendrite (the non-contact pathway) produces calcium responses in the axons only. We interpret the non-contact pathway as damage to adjacent cells releasing diffusible molecules that act on the dendrites. Axonal responses have higher sensitivities and shorter latencies. In contrast, dendritic responses have lower sensitivities and longer latencies. Stimulation of finer, distal dendrites leads to smaller responses than stimulation of coarser, proximal dendrites, as expected if the contact response depends on the geometric overlap of the laser profile and the dendrite diameter. Because the axon signals to the CNS to trigger escape behaviors, we propose that the density of the dendritic meshwork is high not only to enable direct contact with the ovipositor, but also to enable neuronal activation via diffusing signals from damaged surrounding cells. Dendritic contact evokes responses throughout the dendritic arbor, even to regions distant and distal from the stimulus. These dendrite-wide calcium signals may facilitate hyperalgesia or cellular morphological changes following dendritic damage.

Relative Deprivation and Hope: Predictors of Risk Behavior

The belief that one is in a worse situation than similar others (Relative Deprivation) has been associated with involvement in a range of maladaptive escape behaviors, including excessive risk taking. Yet not everyone scoring high on measures of relative deprivation makes maladaptive choices. We hypothesized that hope may ameliorate the negative effects of relative deprivation. In two laboratory-based experiments using a novel risk-taking task (N = 101) we show that hope reduces risk-taking behavior in relatively deprived participants. A third study (N = 122) extended the moderating effect of hope on relative deprivation to real-world risk behavior; increased hope was associated with decreased likelihood of loss of control of one’s gambling behavior in relatively deprived individuals. Nurturing hope in relatively deprived populations may protect them against maladaptive behaviors with potential applications for harm reduction.

Experimental tests of bivalve shell shape reveal potential tradeoffs between mechanical and behavioral defenses

Bivalves protect themselves from predators using both mechanical and behavioral defenses. While their shells serve as mechanical armor, bivalve shells also enable evasive behaviors such as swimming and burrowing. Therefore, bivalve shell shape is a critical determinant of how successfully an organism can defend against attack. Shape is believed to be related to shell strength with bivalve shell shapes converging on a select few morphologies that correlate with life mode and motility. In this study, mathematical modeling and 3D printing were used to analyze the protective function of different shell shapes against vertebrate shell-crushing predators. Considering what life modes different shapes permit and analyzing the strength of these shapes in compression provides insight to evolutionary and ecological tradeoffs with respect to mechanical and behavioral defenses. These empirical tests are the first of their kind to isolate the influence of bivalve shell shape on strength and quantitatively demonstrate that shell strength is derived from multiple shape parameters. The findings of this theoretical study are consistent with examples of shell shapes that allow escape behaviors being mechanically weaker than those which do not. Additionally, shell elongation from the umbo, a metric often overlooked, is shown to have significant effects on shell strength.

Discrete escape responses are generated by neuropeptide-mediated circuit logic

Animals display a plethora of escape behaviors when faced with environmental threats. Selection of the appropriate response by the underlying neuronal network is key to maximize chances of survival. We uncovered a somatosensory network in Drosophila larvae that encodes two escape behaviors through input-specific neuropeptide action. Sensory neurons required for avoidance of noxious light and escape in response to harsh touch, each converge on discrete domains of the same neuromodulatory hub neurons. These gate harsh touch responses via short Neuropeptide F, but noxious light avoidance via compartmentalized, acute Insulin-like peptide 7 action and cognate Relaxin-family receptor signaling in connected downstream neurons. Peptidergic hub neurons can thus act as central circuit elements for first order processing of converging sensory inputs to gate specific escape responses.One Sentence SummaryCompartment-specific neuropeptide action regulates sensory information processing to elicit discrete escape behavior in Drosophila larvae.

The Neural Basis of Escape Behavior in Vertebrates

Escape is one of the most studied animal behaviors, and there is a rich normative theory that links threat properties to evasive actions and their timing. The behavioral principles of escape are evolutionarily conserved and rely on elementary computational steps such as classifying sensory stimuli and executing appropriate movements. These are common building blocks of general adaptive behaviors. Here we consider the computational challenges required for escape behaviors to be implemented, discuss possible algorithmic solutions, and review some of the underlying neural circuits and mechanisms. We outline shared neural principles that can be implemented by evolutionarily ancient neural systems to generate escape behavior, to which cortical encephalization has been added to allow for increased sophistication and flexibility in responding to threat.

Neuronal ON/OFF Motion Detection Circuits Underlying Looming-Evoked Escape Behavior in Drosophila

In Drosophila, early visual processing of motion information segregates in separate ON and OFF pathways. These pathways have been studied in the context of local directional motion detection leading to the encoding of optic flow that provides visual information for flight stabilization. Less is known about their role in detecting impending collision and generating escape behaviors. ‘Looming’, the simulated approach of an object at constant speed towards an animal, provides a powerful stimulus eliciting jump escape behaviors in stationary flies. We presented looming stimuli mimicking the approach of either a dark object on a bright background or a light object on a dark background, while inactivating neurons belonging either to the ON- or the OFF-motion detection pathways by expressing the dominant Drosophila temperature-sensitive mutant shibirets in different cells of the ON/OFF pathway. Inactivation of ON, respectively OFF, neurons led to selective decreases in escape behavior to light, resp. dark, looming stimuli. Quantitative analysis showed a nearly perfect splitting of these effects according to the ON/OFF type of the targeted neural populations. Our results suggest that Drosophila ON/OFF motion detection pathways play an important role in controlling jump escape responses according to looming stimulus polarity. They further imply that the biophysical circuits triggering Drosophila jump escape behaviors likely differ substantially from those characterized in other arthropods.SummaryInactivating fly neurons of the ON or OFF directional motion detection pathways during escape behavior selectively reduced jump responses to light and dark looming stimuli, respectively.