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At least 775 records · Page 43Linked to original sources
PubMed2006

Predator defense along a permanence gradient: roles of case structure, behavior, and developmental phenology in caddisflies.

Species replacements along freshwater permanence gradients are well documented, but underlying mechanisms are poorly understood for most taxa. In subalpine wetlands in Colorado, the relative abundance of caddisfly larvae shifts from temporary to permanent basins. Predators on caddisflies also shift along this gradient; salamanders (Ambystoma tigrinum nebulosum) in permanent ponds are replaced by predaceous diving beetles (Dytiscus dauricus) in temporary habitats. We conducted laboratory and field experiments to determine the effectiveness of caddisfly cases in reducing vulnerability to these predators. We found that larvae of a temporary-habitat caddisfly (Asynarchus nigriculus) were the most vulnerable to salamanders. Two relatively invulnerable species (Limnephilus externus, L. picturatus) exhibited behaviors that reduced the likelihood of detection and attack, whereas the least vulnerable species (Agrypnia deflata) was frequently detected and attacked, but rarely captured because cases provided an effective refuge. Vulnerability to beetle predation was also affected by cases. The stout cases of L. externus larvae frequently deterred beetle larvae, whereas the tubular cases of the other species were relatively ineffective. Two of these vulnerable species (A. nigriculus and L. picturatus) often co-occur with beetles; thus, case construction alone is insufficient to explain patterns of caddisfly coexistence along the permanence gradient. One explanation for the coexistence of these two species with beetles is that they develop rapidly during early summer and pupate before beetle larvae become abundant. One species (L. picturatus) pupates by burying into soft substrates that serve as a refuge. The other (A. nigriculus) builds stone pupal cases, which in field experiments, more than doubles survival compared to organic pupal cases. The combined results of these experiments suggest that caddisfly distributions along permanence gradients depend on a suite of primary and secondary predator defenses that include larval and pupal case structure, predator-specific escape behaviors, and the phenology of larval development.

Ambystoma↗
PubMed1982

The influence of ACTH fragments on habituation of the prey catching behaviour in the European toad (Bufo bufo L.).

Earlier observations on the influence of the ACTH molecule on habituation in toads revealed a capacity, which resembles the improvement of learning and memory processes in rats [6]. In the present investigation ACTH, ACTH1-10 and ACTH11-24 were tested on habituation of turning reaction, a stereotypic component of the prey catching behaviour in the European Toad, Bufo bufo L.. Furthermore the time relationship of the ACTH-effect was determined by injections at different times prior to the beginning of the habituation. ACTH as well as ACTH1-10 caused a dramatic decline in turning reactions per minute towards a prey dummy, when administered 30 min prior to habituation. Therefore, the capacity to facilitate behavioral adaptations must be located mainly in the first ten amino acids of ACTH.

Adrenocorticotropic Hormone↗
PubMed1982

Medial hypothalamic lesions in the rat enhance reactivity and mouse killing but not social aggression.

In rats subjected to lesions of the medial hypothalamus, 8 of 11 animals became mouse killers and all manifested some degree of hyperreactivity to the experimenter. When introduced as intruders into a mixed sex colony group, the lesioned rats did not manifest piloerection nor did they emit flank attacks characteristic of social aggressive behavior. However, the lesioned animals did respond to the attacks of the resident male rats with significantly more counterattacks and biting than did sham-lesioned control rats. Spontaneous mouse killing rats also failed to show a level of social aggressive behavior significantly greater than that of sham-operated control rats, but the spontaneous mouse killers did kill rat pups in the colony groups. Alpha-male rats when introduced as an intruder into a colony group did exhibit piloerection and emit flank attacks characteristic of social aggressive behavior. These results demonstrate that the mouse killing and heightened reactivity associated with medial hypothalamic lesions do not represent an indiscriminant release of all forms of agonistic behavior.

Aggression↗
PubMed1993

Evoked ink release in Aplysia produces inhibition of the siphon withdrawal reflex in neighboring conspecifics.

Aplysia californica exhibit a dramatic defensive reaction, the release of a cloud of dark purple ink, in response to noxious stimuli. Although the neural control of this behavior has been studied rather extensively, the functional significance of the inking response is not well understood. We have found that ink released by animals that are subjected to noxious stimuli rapidly induces inhibition of the tail-elicited siphon withdrawal reflex in neighboring Aplysia. Further experiments indicated that the inhibitor is the ink itself, and not some other substance released by the donor animals. Finally, we examined whether ink-induced inhibition of siphon withdrawal might be a secondary consequence of an elevated competing response such as increased locomotion. We found that locomotion is not affected by the concentrations of ink we employed, indicating that the ink probably modulates the withdrawal reflex directly. Because the neural circuits responsible for both tail-elicited siphon withdrawal and the inking response have already been partly delineated, one can now bring the neurobiological advantages of Aplysia to bear on the ethologically important issue of signaling between conspecifics.

Animal Communication↗
PubMed1984

Encounters in predator-prey systems: a simple discrete model.

Predator-prey systems are often described by exploitation models. These models can mimic experimental data very accurately, but it is sometimes difficult to realize the relationships between the models and the behavior of individual predator and prey animals. A simple discrete model is proposed here that tries to elucidate the connections between: the animals' movements, the predator/prey encounters; and the dynamics in the system as globally represented by the exploitation models. In these models, the term "area of discovery" plays an essential role. This term is shown to be a predictable coefficient that is composed of measurable physical properties of the analyzed predator-prey system. The model takes into account that predators and prey in experimental systems often do not search randomly but prefer some parts of the test area. The model is applied to the mite system Phytoseiulus persimilis/Tetranychus urticae under simple artificial conditions.

Animals↗
PubMed2005

Protein synthesis and the mechanisms of lasting change in anxiety induced by severe stress.

Brief, unprotected exposure of rats to cats (predator stress) may be lastingly anxiogenic in a variety of tests of rodent anxiety. Recent findings suggest that predator stress induced plasticity in neural circuitry implicated in fear learning underlies some of these anxiogenic effects. In addition, recent work implicates a consolidation-like process in the impact of predator stress on anxiety in that effects of predator stress may be interrupted by immediate post stressor pharmacological interventions. The present study tested whether "consolidation" of the anxiogenic effects of predator stress were dependent on protein synthesis. In addition, the study examined whether a protein synthesis dependent reconsolidation-like process was at work when rats were exposed to a cat twice. Anisomycin (210 mg/kg) or vehicle (Tween 80 in saline) was injected subcutaneously 1 min after a single cat exposure (consolidation test paradigm) or a 1 min after a second cat exposure (reconsolidation test paradigm) and behavior tested 7-8 days after predator stress. In the consolidation test paradigm, anisomycin blocked the anxiogenic effects of predator stress in the elevated plus maze (EPM) measured with open arm exploration. Moreover, anisomycin blocked the potentiation of startle by predator stress when rats were startled in the light, but not when startled in the dark. In contrast, the delay of habituation of startle produced by predator stress was unaffected by anisomycin. Suppression of risk assessment in the EPM by predator stress was not affected by anisomycin either. In startle testing, vehicle injection 1 min after predator stress led to a lasting suppression, rather than enhancement of startle response. Vehicle plus predator stress enhanced and prolonged corticosterone level changes sampled over 30-180 min after treatment when compared to handled or predator stressed only rats. In addition, predator stress plus vehicle suppression of startle was blocked by a benzodiazepine anxiolytic (chloradiazepoxide) or the glucorticoid receptor (GR) blocker RU486. Both drugs returned startle to the predator stressed only heightened levels. It is argued that an added anxiogenic effect of vehicle injection plus predator stress leads to a suppression, rather than enhancement of startle. Startle suppression appears to be mediated, in part, by activation of GR by corticosterone which engages a protein synthesis dependent process, since anisomycin blocked the startle suppressive effects of vehicle. Startle suppression also appeared to be independent of the startle enhancing effect of predator stress and in competition with it. Since predator stress may model aspects of hyperarousal associated with post traumatic stress disorder (PTSD), implications of these findings for understanding of mechanisms of initiation of the disorder and for treatment are discussed.

Analysis of Variance↗
PubMed2005

How does the presence of predators influence the persistence of antipredator behavior?

We developed a virtual world to study the effect of predators on predator recognition. We trained a neural network to discriminate between the shapes of simulated aerial and terrestrial predators and non-predators. Then, the network's weighting values were fixed into the genomes of a set of autonomous agents. These animats were required to eat, avoid death due to starvation, and avoid predation, by fleeing from approaching predators. We systematically varied the predator's lethality, the mutation rate, the cost of fleeing a predator, and the presence or absence of aerial and terrestrial predators. We used ANOVA to analyse the average recognition ability (a measure of directional selection) and the standard deviation of recognition ability (a measure of relaxed selection) after 500 generations of selection. Mutation rate and the cost of flight had the greatest effect on both the average and standard deviation of recognition abilities. The loss of all predators relaxed selection on predator recognition abilities. The loss of specific predators had complex effects on recognition abilities. Persistence is largely influenced by escape costs.

Animals↗
PubMed2005

TMT-induced autonomic and behavioral changes and the neural basis of its processing.

One of the main interests in the field of neuroscience is the investigation of the neural basis of fear. During recent years, an increasing number of studies have used trimethylthiazoline (TMT), a component of red fox feces, as a stimulus to induce fear in predator naive rats, mice, and voles. The aim of the present review is to summarize these studies. We present an overview to the autonomic and behavioral changes that are induced by TMT exposure. Then, we summarize the small number of studies that have examined the neural processing of the TMT stimulus. Finally, we compare these studies with those using a natural predator or predator odor to induce fear and discuss the possible use of TMT exposure in rodents as an animal model of unconditioned fear in humans.

Animals↗
PubMed2005

Feeding behavior modulation in the leopard lizard (Gambelia wislizenii): effects of noxious versus innocuous prey.

Feeding, a fundamentally rhythmic behavior in many animals, is expected to exhibit modulation with respect to prey type. Using high-speed videography (200 frames(-1)) and kinematic analysis, we investigated prey-processing behavior in the long-nosed leopard lizard (Gambelia wislizenii). The effects of two prey types were examined, innocuous immature crickets (Acheta domesticus) and noxious stinging hymenopterans (honeybees [Apis mellifer] and yellow jackets [Vespula sp.]). Stinging hymenopterans are processed more extensively, with higher gape-cycling frequencies, and for a greater duration than are crickets. Generalized tetrapod feeding models were used as a framework to test the hypothesis that gape profile characteristics are modulated in response to prey noxiousness. Cricket processing generally fits the models, but hymenopteran processing departs from typical model parameters. In particular, the SO phase is absent to barely detectable during hymenopteran processing. This likely represents an effect of extrinsic neural input on a centrally directed rhythmic motor pattern, possibly to avoid being stung. Differences in the capture behavior of crickets versus hymenopterans indicate that G. wislizenii assesses prey noxiousness before physical contact with prey and modifies its capture behavior accordingly. These results add to the growing body of evidence that sensory information can play a critical role in shaping stereotyped rhythmic behaviors in non-mammalian tetrapods.

Analysis of Variance↗
PubMed1984

A global model of the neural mechanisms responsible for visuomotor coordination in toads.

A model of how the nervous system of toads processes visual information to control motor behaviour is proposed. The problem of visuomotor coordination in toads is studied through the integration of two different approaches: a top-down approach through schema theory developed in the studies of cognitive psychology, artificial intelligence and brain theory; and a bottom-up approach through the integration of physiological, anatomical, ethological, and neural modelling. The model proposes that visual information is processed in a parallel distributed way through different brain layers whose interaction defines the proper motor response for that specific situation. It is postulated that visual processing of information is organized into main schemata, which set the goal to be attained and, depending on the specific circumstances of the animal, activates different brain layers; the main schemata may use other schemata to solve a specific subproblem to reach the schemata, and a programme of schema co-ordination. With this model we have simulated how toads plan their route to reach a prey or the route to go away form a predator, depending on the state of their three-dimensional world. The model postulates specific hypotheses that could be tested experimentally on the processing of information in the toad's nervous system.

Animals↗
PubMed2003

Biodiversity, habitat area, resource growth rate and interference competition.

For the majority of species, per capita growth rate correlates negatively with population density. Although the popular logistic equation for the growth of a single species incorporates this intraspecific competition, multi-trophic models often ignore self-limitation of the consumers. Instead, these models often assume that the predator-prey interactions are purely exploitative, employing simple Lotka-Volterra forms in which consumer species lack intraspecific competition terms. Here we show that intraspecific interference competition can account for the stable coexistence of many consumer species on a single resource in a homogeneous environment. In addition, our work suggests a potential mechanism for field observations demonstrating that habitat area and resource productivity strongly positively correlate to biodiversity. In the special case of a modified Lotka-Volterra model describing multiple predators competing for a single resource, we present an ordering procedure that determines the deterministic fate of each specific consumer. Moreover, we find that the growth rate of a resource species is proportional to the maximum number of consumer species that resource can support. In the limiting case, when the resource growth rate is infinite, a model with intraspecific interference reduces to the conventional Lotka-Volterra competition model where there can be an unlimited number of coexisting consumers. This highlights the crucial role that resource growth rates may play in promoting coexistence of consumer species.

Animals↗