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At least 685 records · Page 38Linked to original sources
PubMed2001

Evolution and function of auditory systems in insects.

While the sensing of substrate vibrations is common among arthropods, the reception of sound pressure waves is an adaptation restricted to insects, which has arisen independently several times in different orders. Wherever studied, tympanal organs were shown to derive from chordotonal precursors, which were modified such that mechanosensitive scolopidia became attached to thin cuticular membranes backed by air-filled tracheal cavities (except in lacewings). The behavioural context in which hearing has evolved has strongly determined the design and properties of the auditory system. Hearing organs which have evolved in the context of predator avoidance are highly sensitive, preferentially in a broad range of ultrasound frequencies, which release rapid escape manoeuvres. Hearing in the context of communication does not only require recognition and discrimination of highly specific song patterns but also their localisation. Typically, the spectrum of the conspecific signals matches the best sensitivity of the receiver. Directionality is achieved by means of sophisticated peripheral structures and is further enhanced by neuronal processing. Side-specific gain control typically allows the insect to encode the loudest signal on each side. The filtered information is transmitted to the brain, where the final steps of pattern recognition and localisation occur. The outputs of such filter networks, modulated or gated by further processes (subsumed by the term motivation), trigger command neurones for specific behaviours. Altogether, the many improvements opportunistically evolved at any stage of acoustic information-processing ultimately allow insects to come up with astonishing acoustic performances similar to those achieved by vertebrates.

Animals↗
PubMed2005

Gregarious behaviour of evasive prey.

Gregarious behavior of potential prey was explained by Hamilton (1971) on the basis of risk-sharing: The probability of being picked up by a predator is small when one makes part of a large aggregate of prey. This argument holds only if the predator chooses its victims at random. It is not the case for herds of evasive prey in the open, where prey's gregarious behavior, favorable for the fast group members, makes it easier for the predator to home in on the slowest ones. We show conditions under which gregarious behavior of the relatively fast prey individuals leaves slowest prey with no other choice but to join the group. Failing to do so would signal their vulnerability, making them a preferred target for the predator. Analysis of an n + 1 player game of a predator and n unequal prey individuals clarifies conditions for fully gregarious, partially gregarious, or solitary behavior of the prey.

Algorithms↗
PubMed2005

Prey size selection and distance estimation in foraging adult dragonflies.

To determine whether perching dragonflies visually assess the distance to potential prey items, we presented artificial prey, glass beads suspended from fine wires, to perching dragonflies in the field. We videotaped the responses of freely foraging dragonflies (Libellula luctuosa and Sympetrum vicinum-Odonata, suborder Anisoptera) to beads ranging from 0.5 mm to 8 mm in diameter, recording whether or not the dragonflies took off after the beads, and if so, at what distance. Our results indicated that dragonflies were highly selective for bead size. Furthermore, the smaller Sympetrum preferred beads of smaller size and the larger Libellula preferred larger beads. Each species rejected beads as large or larger than their heads, even when the beads subtended the same visual angles as the smaller, attractive beads. Since bead size cannot be determined without reference to distance, we conclude that dragonflies are able to estimate the distance to potential prey items. The range over which they estimate distance is about 1 m for the larger Libellula and 70 cm for the smaller Sympetrum. The mechanism of distance estimation is unknown, but it probably includes both stereopsis and the motion parallax produced by head movements.

Animals↗
PubMed1997

Sensory modulation and behavioral choice during feeding in the Australian frog, Cyclorana novaehollandiae.

This study investigates how visual and tactile sensory information, as well as biomechanical effects due to differences in physical characteristics of the prey, influence feeding behavior in the frog Cyclorana novaehollandiae. Video motion analysis was used to quantify movement patterns produced when feeding on five prey types (termites, waxworms, crickets, mice and earthworms). Twelve kinematic variables differed significantly among prey types, and twelve variables were correlated with prey characteristics (including mass, length, height and velocity of movement). Results indicate that C. novaehollandiae uses a different strategy to capture each prey type. Visual assessment of prey characteristics appeared to be more important in modulating feeding behavior that tactile cues or biomechanical effects. We propose a hierarchical hypothesis of behavioral choice, in which decisions are based primarily on visual analysis of prey characteristics. In this model, the frogs first choose between jaw prehension and tongue prehension based on prey size. If they have chosen jaw prehension, they next choose between upward or downward head rotation based on length and height of the prey. If they have chosen tongue prehension, they next choose between behavior for fast and slow prey. Final decisions may be the result of behavioral fine tuning based on tactile feedback.

Aging↗
PubMed2003

Resource-mediated impact of spider predation risk on performance in the grasshopper Ageneotettix deorum (Orthoptera: Acrididae).

In response to increased exposure to predators when searching for food, many prey increase the frequency of antipredator behaviors, potentially reducing foraging rate and food intake. Such direct, nonlethal interactions between predators and prey resulting in reduced food intake can indirectly influence lifecycle development through effects on growth, developmental rate, and survival. We investigated the general hypothesis that individual performance of a herbivorous insect can be negatively affected when exposed to nonlethal predation risk, and that the response can be mediated by food quality. This hypothesis was tested using the common rangeland grasshopper Ageneotettix deorum with and without exposure to common wolf spider predators (Lycosidae, Schizocosa spp.) on both untreated natural and fertilized vegetation. All spiders were rendered temporarily incapable of direct feeding by restricting function of the chelicerae with beeswax. Detectable responses by grasshoppers to spiders indicate indirect consequences for lifecycle development. Grasshopper performance was measured as hind femur growth, duration of nymphal lifecycle stages, and survivorship in a caged field experiment conducted over 2 years. Grasshoppers developed faster and grew 3-5% larger when allowed to forage on fertilized vegetation in the absence of risk from a spider predator. Failure-time analysis illustrated enhanced survival probability in response to elevated food quality and the negative effects of grasshopper susceptibility to nonlethal predation risk. Performance on food of relatively low, ambient quality with no predation risk equaled that of grasshoppers caged with high quality vegetation in the presence of a modified spider. Increased resource quality can clearly moderate the negative life history responses caused by the behavioral modification of grasshoppers when exposed to spider predation risk, a compensatory response.

Adaptation, Physiological↗
PubMed2004

Intraguild predation and successful invasion by introduced ladybird beetles.

Introductions of two ladybird beetle (Coleoptera: Coccinellidae) species, Coccinella septempunctata and Harmonia axyridis, into North America for aphid biocontrol have been followed by declines in native species. We examined intraguild predation (IGP) between larvae of these two exotic species and larvae of the two most abundant native coccinellids in eastern Washington State, C. transversoguttata and Hippodamia convergens. In pairings between the two native species in laboratory microcosms containing pea ( Pisum sativum) plants, neither native had a clear advantage over the other in IGP. When the natives were paired with either Harmonia axyridis or C. septempunctata, the natives were more frequently the victims than perpetrators of IGP. In contrast, in pairings between the exotic species, neither had an IGP advantage, although overall rates of IGP between these two species were very high. Adding alternative prey (aphids) to microcosms did not alter the frequency and patterns of relative IGP among the coccinellid species. In observations of encounters between larvae, the introduced H. axyridis frequently survived multiple encounters with the native C. transversoguttata, whereas the native rarely survived a single encounter with H. axyridis. Our results suggest that larvae of the native species face increased IGP following invasion by C. septempunctata and H. axyridis, which may be contributing to the speed with which these exotic ladybird beetles displace the natives following invasion.

Animals↗
PubMed2006

Field evidence of an airborne enemy-avoidance kairomone in wolf spiders.

Hogna helluo, Pardosa milvina, and Trochosa ruricola are co-occurring species of wolf spiders within agricultural fields in the eastern USA. The largest species, H. helluo, is a common predator of the two smaller species, P. milvina and T. ruricola. H. helluo frequently resides within soil fissures where P. milvina and T. ruricola may be attacked when they enter or walk near these fissures. We tested the ability of P. milvina and T. ruricola to avoid H. helluo-containing burrows by detecting airborne enemy-avoidance kairomones associated with H. helluo. To simulate soil fissures and control for visual and vibratory means of predator detection, we baited funneled pitfall traps with one of the following (N = 20 traps/treatment): (1) blank (empty trap); (2) one house cricket (Acheta domesticus); (3) one adult female H. helluo; and (4) one adult male H. helluo. Over two separate 3-d periods, we measured pitfall capture rates of P. milvina and T. ruricola as well as other incidentally captured ground-dwelling arthropods. During the day, male P. milvina showed significant avoidance of pitfall traps baited with H. helluo of either sex but showed no avoidance of empty traps or those containing crickets. At night, male T. ruricola showed a qualitatively similar pattern of avoiding H. helluo-baited traps, but the differences were not statistically significant. We found no evidence that other ground-dwelling arthropods either avoided or were attracted to H. helluo-baited traps. This study suggests that an airborne enemy-avoidance kairomone may mediate behavior among male P. milvina in the field.

Air↗
PubMed1986

Glossopharyngeal and tectal influences on tongue-muscle motoneurons in the Japanese toad.

Anuran tongue-muscle motoneurons receive excitatory inputs both from the glossopharyngeal nerve afferents and from the optic tectum. As a step toward elucidating the neural bases for controlling the tongue movements, we searched intracellularly for the neuronal pathways from the glossopharyngeal afferents to the tongue-muscle motoneurons in paralyzed Japanese toads. The electrical stimuli applied to the glossopharyngeal nerve (ipsilateral lingual branch) evoked polysynaptic excitatory postsynaptic potentials (EPSPs) in tongue-protractor motoneurons and mixed mono- and polysynaptic EPSPs in tongue-retractor motoneurons. Furthermore, we investigated the mode of the convergency of the excitatory inputs from the glossopharyngeal nerve and those from the optic tectum. A spatial facilitation was observed between the tectal EPSPs and the glossopharyngeal EPSPs in some motoneurons tested. These results suggest the existence of common excitatory premotor interneurons, on which the tectal descending volleys and the glossopharyngeal afferent volleys converge.

Animals↗