Intersection of motor volumes predicts the outcome of ambush predation of larval zebrafish

ABSTRACTEscape maneuvers are key determinants of animal survival and are under intense selection pressure. A number of escape maneuver parameters contribute to survival, including response latency, escape speed and direction. However, the relative importance of these parameters is context dependent, suggesting that interactions between parameters and predatory context determine the likelihood of escape success. To better understand how escape maneuver parameters interact and contribute to survival, we analyzed the responses of larval zebrafish (Danio rerio) to the attacks of dragonfly nymphs (Sympetrum vicinum). We found that no single parameter explains the outcome. Instead, the relative intersection of the swept volume of the nymph's grasping organs with the volume containing all possible escape trajectories of the fish is the strongest predictor of escape success. In cases where the prey's motor volume exceeds that of the predator, the prey survives. By analyzing the intersection of these volumes, we compute the survival benefit of recruiting the Mauthner cell, a neuron in anamniotes devoted to producing escapes. We discuss how the intersection of motor volume approach provides a framework that unifies the influence of many escape maneuver parameters on the likelihood of survival.

Design Of Lunar-Gravity-Assisted Escape Trajectories

Lunar gravity assist is a means to boost the energy and C3 of an escape trajectory. Trajectories with two lunar gravity assists are considered and analyzed. Two approaches are applied and tested for the design of missions aimed at Near-Earth asteroids. In the first method, indirect optimization of the heliocentric leg is combined to an approximate analytical treatment of the geocentric phase for short escape trajectories. In the second method, the results of pre-computed maps of escape C3 are employed for the design of longer Sun-perturbed escape sequences combined with direct optimization of the heliocentric leg. Features are compared and suggestions about a combined use of the approaches are presented. The techniques are efficiently applied to the design of a mission to a near-Earth asteroid.

Border threads : ethnographic tales of escape, agency, and violence in a shelter in Pakistan

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI--COLUMBIA AT REQUEST OF AUTHOR.] This study highlights the theoretical usefulness of viewing domestic violence shelters through the conceptual framework of border-crossing and borders. Utilizing feminist ethnography as a research method to explore the socio-cultural aspects of a domestic violence shelter in Pakistan, it asks the following questions: How do survivors of domestic violence (women) reach the shelter? How does the shelter enable women who have suffered domestic abuse to engage in descriptions that counter outside efforts to silence them? How does shelter as a space of protection both enable social change and reproduce structures of domination? Based on ethnographic observations and interviews with 45 shelter residents, shelter staff, and feminist scholars, this study demonstrates that survivors of domestic violence, specifically women belonging to a lower socio-economic demographic, construct and expend heroic forms of agency in formulating specific escape trajectories and are in effect border-crossers. Importantly, it found that shelter residents re-construct themselves through narratives of violence made possible through temporary pockets of articulation. Absence of supportive socio-political and economic structures that may enable shelter residents to embark on emancipatory exit trajectories converts the agency utilized to escape violent homes into forms that are excessive.

Geometrical model explains multiple preferred escape trajectories of fish

To evade predators, many prey perform rapid escape movements. The resulting escape trajectory (ET) – measured as the angle of escape direction relative to the predator’s approach path – plays a major role in avoiding predation. Previous geometrical models predict a single ET; however, many animals (fish and other animal taxa) show highly variable ETs with multiple preferred directions. Although such a high ET variability may confer unpredictability, preventing predators from adopting counter-strategies, the reasons why animals prefer specific multiple ETs remain unclear. Here, we constructed a novel geometrical model in which Tdiff (the time difference between the prey entering the safety zone and the predator reaching that entry point) is expected to be maximized. We tested this prediction by analyzing the escape responses of Pagrus major attacked by a dummy predator. At each initial body orientation of the prey relative to the predator, our model predicts a multimodal ET with an optimal ET at the maximum Tdiff (Tdiff,1) and a suboptimal ET at a second local maximum of Tdiff (Tdiff,2). Our experiments show that when Tdiff, 1–Tdiff, 2 is negligible, the prey uses optimal or suboptimal ETs to a similar extent, in line with the idea of unpredictability. The experimentally observed ET distribution is consistent with the model, showing two large peaks at 110–130° and 170–180° away from the predator. Because various animal taxa show multiple preferred ETs similar to those observed here, this behavioral phenotype may result from convergent evolution that combines maximal Tdiff with a high level of unpredictability.Significance StatementAnimals from many taxa escape from suddenly approaching threats, such as ambush predators, by using multiple preferred escape trajectories. However, the reason why these multiple preferred escape trajectories are used is still unknown. By fitting a newly constructed model to the empirical escape response data, we show that the seemingly complex multiple preferred escape trajectories can arise from a simple geometrical rule which maximizes the time difference between when the prey enters the safety zone and when the predator reaches that entry point. Our results open new avenues of investigation for understanding how animals choose their escape trajectories from behavioral and neurosensory perspectives.

Intersection of motor volumes predicts the outcome of ambush predation of larval zebrafish

The escape maneuvers of animals are key determinants of their survival. Consequently these maneuvers are under intense selection pressure. Current work indicates that a number of escape maneuver parameters contribute to survival including response latency, escape speed, and direction. This work has found that the relative importance of these parameters is context dependent, suggesting that interactions between escape maneuver parameters and the predatory context together determine the likelihood of escape success. However, it is unclear how escape maneuver parameters interact to contribute to escape success across different predatory contexts. To clarify these issues, we investigated the determinants of successful escape maneuvers by analyzing the responses of larval zebrafish to the attacks of dragonfly nymphs. We found that the strongest predictor of the outcome was the time needed for the nymph to reach the fish’s initial position at the onset of the attack, measured from the time that the fish initiates its escape response. We show how this result is related to the intersection of the swept volume of the nymph’s grasping organs with the volume containing all possible escape trajectories of the fish. By analyzing the intersection of these volumes, we compute the survival benefit of recruiting the Mauthner cell, a neuron in anamniotes devoted to producing escapes. We discuss how escape maneuver parameters interact in determining escape response. The intersection of motor volume approach provides a framework that unifies the influence of many escape maneuver parameters on the likelihood of survival.

Enhancing solidarity through dispreferred format

The Korean clausal-connective nuntey, a particle indicating ‘background’, is analysed in terms of the ‘my-side-revealing’ practice that projects ‘escape trajectories’ in which an incipiently formulated action is foreshown to be retractable. For instance, in response to an offer, incipient non-compliance, marked by nuntey, may be leveraged into acceptance; here, the speaker emerges as a ‘markedly self-sufficient’ beneficiary who ostensibly orients to minimising the cost of burden on the part of the offer-maker. The offer-maker, on his/her part, emerges as a ‘markedly other-attentive’ benefactor through deferentially overriding the recipient’s nuntey-marked account adumbrating a dispreferred response. Across different contexts, the nuntey-marked response, with its expansion-relevant character, embodies the speaker’s normative orientation, furnishing the opportunity for the participants to manage face, morality, and solidary relationships. Cross-linguistic implications are noted with reference to the self-indulgent practice of ‘distancing’, with the hearer being mobilised as a co-member to accountably co-leverage the current action with upgraded affiliation.