Stable fly, Stomoxys calcitrans, mouthpart removal influences stress and anticipatory responses in mice

Abstract Biting fly attack induces a variety of stress and anxiety related changes in the physiology and behaviour of the target animals. Significant reductions in pain, or more appropriately, nociceptive sensitivity (latency of a foot-lifting response to an aversive thermal stimulus), are evident in laboratory mice after a 1 h exposure to stable flies, Stomoxys calcitrans. The role of the various components of biting fly attack in the development of this stress-induced reduction in pain sensitivity (analgesia) is, however, unclear. This study demonstrates that fly-naive mice do not exhibit a stress-induced analgesia when exposed to stable flies whose biting mouthparts have been removed. In contrast, mice that have been previously exposed to intact stable flies exhibit significant analgesia when exposed to flies that are incapable of biting. However, the level of analgesia induced is lower than that elicited by exposure to intact stable flies. Exposure to non-biting house flies, Musca domestica , has no effect on nociceptive sensitivity. It appears that the actual bite of the stable fly is necessary for the induction of analgesia and probably other stress and anxiety associated responses in fly naive mice. However, mice rapidly learn to recognize biting flies and exhibit significant, possibly anticipatory analgesic responses to the mere presence of biting flies.     

The Use of Standard Aggression Testing Methods to Predict Combat Behaviour and Contest Outcome in Rivulus marmoratus Dyads (Teleostei: Cyprinodontidae)

Aggression plays an important role in animal contests, but the extent to which aggression correlates with dominance has been a topic of much debate. The relationship between aggression and dominance ability in the hermaphroditic fish, Rivulus marmoratus , was investigated using three standard protocols, the mirror test (Mi), model test (Mo), and standard opponent test (So). In each, display latency, attack latency, and biting frequency were quantified for a test individual towards its opponent. The general rank-order for eliciting strength of the three different stimuli was Mi > So > Mo. The relationships between the individual indices from the standard tests and three dyadic contest variables, initiator of display, initiator of attack, and winner, were analysed in contests between previously tested pairs to ascertain how well the standard protocols predicted dyadic contest behaviour/outcome. Display and attack latencies in the standard tests did not predict the level of analogous combat behaviour. Biting frequency differences between individuals in a pair in the So and Mo tests as well as display latency differences in the Mi test contributed to predictions of contest outcome. The individual that scored higher, relative to its opponent, won a significantly greater proportion of the bouts. These findings demonstrate the importance of relative differences in aggression in determining dominance. However, the predictive value of standard test behaviour is test-specific and, based on the available literature, depends on both the species used and the context in which they are employed.     

Attempts to determine the status of electroshock-induced attack in male laboratory mice

An attempt was made using a combination of simple experimental manipulations and videotape recorder (VTR) analysis of bite targets employed to determine whether electroshock-induced attack on anosmic opponents in laboratory mice was an offensive or a defensive behaviour. VTR analysis suggested that ventral surface biting was more evident in this form of attack than in social conflict. Individually- and group-housed males showed similar levels of fighting on exposure to electroshock, but dominant males from pairs showed greater attack than their subordinate partners. Zinc sulphate-induced anosmia, 36 h of food deprivation, castration and lithium chloride treatment reduced electroshock-induced attack. Although significant changes were not obtained, there was some evidence that acute treatment with dexamethasone or ACTH augmented this behaviour. The direction of these changes is similar to that seen with social conflict, and it is suggested that electroshock-induced attack in the mouse (unlike the rat) is largely an aggressive offensive behaviour. The high incidence of ventral surface biting may be a consequence of the upright postures assumed on subjecting the animals to electroshock.     

Effects of nicotine on target biting and resident-intruder attack

The effects of acute administration of nicotine on target biting (defensive) and resident-intruder (offensive) attack of male mice were assessed. In the target biting procedure confined mice received tail shock on a fixed time, 2-min schedule. Under baseline conditions, biting attack directed toward an inanimate target occurred at three distinct rates. A high target biting rate (13.5 +/- 3.8 bites/15 sec) followed shock delivery, an intermediate biting rate (9.6 +/- 4.1 bites/15 sec) occurred during the inter-shock interval, and a low biting rate (1.0 +/- 0.5 bites/15 sec) occurred during a tone stimulus which signalled the impending shock. Nicotine (administered IP, 15 min presession) reduced post-shock and inter-shock interval target biting in a dose-dependent manner (ED50 values estimated at 0.13 and 0.14 mg/kg, respectively) but exerted more variable effects on target biting during the tone. In the resident-intruder paradigm the same mice were exposed to an intruder introduced into its home cage for a 10-min test session. Under baseline conditions, residents directed 20 +/- 3.2 biting attacks toward the intruder during the session with an average latency of 89 +/- 40 sec to the first attack. Nicotine caused a dose-dependent decrease in this attack behavior (ED50 values estimated to be 0.48 and 0.49 mg/kg, respectively). These observations are interpreted to indicate that nicotine has an increased potency at reducing "defensive" aggression.     

Active defence of herbivorous hosts against parasitism: Adult parasitoid mortality risk involved in attacking a concealed stemboring host

Phytophagous insects have several defence strategies to defend themselves against attack by parasitic wasps. Larval lepidopteran hosts can defend themselves actively to prevent oviposition by the parasitoid. Among the aggressive kinds of behaviour exhibited by hosts against parasitoids are violent wriggling, biting and spitting. The behaviour of the braconid parasitoid Cotesia sesamiae attacking stemboring larvae inside their feeding tunnel in the plant stem was investigated in maize and sugarcane stem pieces and transparent artificial tunnels. Attacking a defending stemborer host inside the confined space of a tunnel was shown to be risky for the female parasitoid. A considerable proportion (25%) of female wasps were killed in their attempt to attack the spitting and biting host. No difference was found in the behaviour of C. sesamiae attacking the suitable host Sesamia calamistis or the unsuitable host Eldana saccharina. The consequences of this high mortality risk involved in each host attack is discussed in relation to the ecology of the parasitoid.     

Multicomponent alarm pheromones in the mandibular glands of major workers of the African weaver ant, Oecophylla longinoda

ABSTRACT. The complex system of alarm communication in Oecophylla longinoda is described. The mandibular gland secretion of major workers releases in other major workers a complex pattern of behaviour, which includes components of alerting, attraction and biting. The main constituents of the secretion are hexanal and 1-hexanol, which release alerting and attraction respectively. Of the thirty or so trace components, at least two, 2-butyl-2-octenal and 3-undecanone, act as markers for attack. In combination, these components produce a sequential message in space and time, dependent on their relative proportions, volatilities and threshold concentrations for behavioural reponses.     

Studies on tube restraint-induced attack on a metal target by laboratory mice

This study examines factors influencing the attack on a metal target by laboratory ‘TO’ strain mice confined within a narrow perspex tube and contrasts this form of behaviour with attack seen in less equivocal forms of ‘aggression test’. The effects of sex, housing condition, reproductive experience, density, anosmia and castration (in the male) were systematically examined. This ‘model’ of ‘aggression’ shows few parallels with social conflict, parental defense and electroshock-induced forms of attack as none of the above manipulations influenced the level of target biting in this situation. Thus, in spite of claims that tube restraint-induced attack may show parallels with intermale aggression, the data suggest that it involves a totally different motivation.     

Detailed analysis of fighting in polecats (Mustelidae) using ciné film

The phenomenon of fighting was investigated under laboratory conditions using polecats ( Mustela putorius, M. furo and interspecific hybrids). Diadic interactions between male polecats were recorded on 16 mm cine film in an unfamiliar area of 16 m², one individual having been introduced ten minutes before its opponent.
The behaviour patterns involved in fighting are described and their frequencies of occurrence, duration and average bout lengths specified. Biting, which occupied 41% of the animal's time in fighting, and attacking, which made up 27% of the bouts of behaviour, were the most important actions involved in fighting. Polecats most commonly bite their opponent's neck and bites in this region were the longest in duration. Success in gaining a bite was influenced by the opponent's behaviour at the time of the attack.
Polecats fight when one individual bites its opponent and the opponent retaliates by biting; bite was shown to be the commonest response to being bitten. The length of a fight appears to be determined by the levels of motivation to bite of the two opponents, while biting and being bitten operate as a positive feed back mechanism. The fight terminates when the more aggressive opponent ceases to make spontaneous attacks. The reasons why one individual wins a fight are that it consistently spends more time than its opponent in biting, it persists for longer in making spontaneous attacks and its method of attacking is more efficient.     

Synaptic plasticity in the mesolimbic dopamine system

Long-term potentiation (LTP) and long-term depression (LTD) are thought to be critical mechanisms that contribute to the neural circuit modifications that mediate all forms of experience-dependent plasticity. It has, however, been difficult to demonstrate directly that experience causes long-lasting changes in synaptic strength and that these mediate changes in behaviour. To address these potential functional roles of LTP and LTD, we have taken advantage of the powerful in vivo effects of drugs of abuse that exert their behavioural effects in large part by acting in the nucleus accumbens (NAc) and ventral tegmental area (VTA); the two major components of the mesolimbic dopamine system. Our studies suggest that in vivo drugs of abuse such as cocaine cause long-lasting changes at excitatory synapses in the NAc and VTA owing to activation of the mechanisms that underlie LTP and LTD in these structures. Thus, administration of drugs of abuse provides a distinctive model for further investigating the mechanisms and functions of synaptic plasticity in brain regions that play important roles in the control of motivated behaviour, and one with considerable practical implications.     

A brief report on intra-species aggressive biting in a goat herd

This study aimed at analysing the effects of age, horn and places on biting and butting as intra-species aggressive activities. Seventy-two Turkish Saanen goats were used as animal material and 22,686 aggressive behaviours were recorded in different places from a total of 118 h direct observation. Of the observations of aggressive behaviours, 32.7% was biting behaviour and the rest was butting behaviour. The frequency of biting behaviour in 3 or more years old goats was significantly higher than that of biting behaviour in 1 and 2 years old animals (P ≤ 0.01). The observations revealed that horned or hornless goats exhibited biting behaviour; however the frequency of biting behaviour in hornless goats was 2.38 times higher than in horned goats (P ≤ 0.01). Biting and butting behaviours were found to be well correlated with the area of places (P ≤ 0.01). As the area of places got narrowed, the frequency of biting increased. However, such a trend was not observed in butting behaviour. The frequency of butting behaviour again increased with the increase in social hierarchy (P ≤ 0.01), whereas the frequency of biting behaviour was not affected by social hierarchy (P = 0.30). In conclusion, intra-species biting behaviour, which is thought to have developed as a result of horn absence, should be questioned whether this is unique to the herd or to the genotype.     

Connecting behaviour and performance: the evolution of biting behaviour and bite performance in bats

Variation in behaviour, performance and ecology are traditionally associated with variation in morphology. A neglected part of this ecomorphological paradigm is the interaction between behaviour and performance, the ability to carry out tasks that impact fitness. Here we investigate the relationship between biting behaviour and performance (bite force) among 20 species of ecologically diverse bats. We studied the patterns of evolution of plasticity in biting behaviour and bite force, and reconstructed ancestral states for behaviour and its plasticity. Both behavioural and performance plasticity exhibited accelerating evolution over time, and periods of rapid evolution coincided with major dietary shifts from insect‐feeding to plant‐feeding. We found a significant, positive correlation between behavioural plasticity and bite force. Bats modulated their performance by changing their biting behaviour to maximize bite force when feeding on hard foods. The ancestor of phyllostomids was likely a generalist characterized by high behavioural plasticity, a condition that also evolved in specialized frugivores and potentially contributed to their diversification.     

Juvenile hormone regulation of the second biting cycle in Culex pipiens

Juvenile hormone regulation of the second biting cycle was studied in Culex pipiens by allatectomizing mosquitoes at daily intervals after the first blood meal. Mosquitoes oviposited and were tested for biting 2 days later. Allatectomy on days 1 through 4 prevented biting in a high percentage of females, indicating that juvenile hormone was required for a second biting cycle. When allatectomy was delayed 6 or more days after the first blood meal, the mosquitoes took a second blood meal after oviposition even though eggs were retained at the time of allatectomy. Thus, egg retention did not prevent mosquitoes from releasing juvenile hormone for a second biting cycle. Unoperated mosquitoes also bit when they were forced to retain eggs after the first blood meal. However, these mosquitoes only fed on blood if they were confined on or near the host; they would not feed in cages where host seeking was required to locate the host. Based on these findings, it appeared that oviposition was necessary to initiate host-seeking behaviour, whereas juvenile hormone release initiated biting. These results, in conjunction with earlier work demonstrating juvenile hormone induction of the first biting cycle, indicated that alternating periods of juvenile hormone production and oviposition regulate the cyclic patterns of biting and host-seeking behaviour throughout the life of the mosquito.     

Visual and olfactory responses of haematophagous Diptera to host stimuli

Key biotic and environmental constraints on the host-orientated behaviour of haematophagous Diptera are summarized. For each major group of biting Diptera, responses to host stimuli are reviewed, including activation and ranging behaviour, long-range and short-range olfactory responses and visual responses. Limitations to the comparison of results between groups of species, and the practical problems of experimental method and equipment are discussed.     

Food chemical discriminations by an herbivorous lizard, Corucia zebrata

Adjustment of chemosensory response to diet should be apparent in evolutionary changes corresponding to dietary shifts. Because most lizards are generalist predators of small animals, relationships between chemosensory behavior and diet are difficult to detect. Nevertheless, the evolution of herbivory by a small number of lizards provides an opportunity to detect any corresponding change in response to plant chemicals. I studied tongue-flicking and biting by the large, herbivorous scincid lizard Corucia zebrata in response to chemical cues from crickets, romaine lettuce, and control stimuli presented on cotton swabs. The skinks exhibited significantly stronger response to plant and animal chemicals than to controls for several variables: greater number of individuals that bit swabs, shorter latency to bite, greater rate of tongue-flicks, and greater tongue-flick attack score. The clearest differences were observed for tongue-flick attack score, a composite variable that combines the effects of tongue-flicking and biting. An insectivorous member of the same subfamily, Scincella lateralis, shows strong tongue-flicking and biting response to chemical prey cues, but not to plant chemicals. This suggests that response to plant chemicals by C. zebrata may have evolved in tandem with the incorporation of plants into the diet and that response to cricket chemicals has been retained, perhaps due to similarities between plant and animal food. The findings support the hypothesis that dietary shifts induce corresponding changes in chemosensory response, but provide only a single independent contrast for a study of correlated evolution between plant diet and chemosensory response to plants. J. Exp. Zool. 286:372-378, 2000.     

Inhibition by talipexole, a thiazolo-azepine derivative, of dopaminergic neurons in the ventral tegmental area.

A microiontophoretic study using rats anesthetized with chloral hydrate and immobilized with gallamine triethiodide was carried out to compare the effect of talipexole (B-HT 920 CL2:2-amino-6-allyl-5,6,7,8-tetrahydro-4H-thiazolo [4,5-d]-azepine-dihydrochloride), a dopamine autoreceptor agonist, on dopaminergic neurons in the ventral tegmental area (VTA) to non-dopaminergic neurons in the VTA. VTA neurons were classified into two types according to the responses to antidromic stimulation of the nucleus accumbens (Acc): type I neurons with a long spike latency (8.69 +/- 0.24 msec) upon Acc stimulation and low spontaneous firing rate (6.80 +/- 1.34/sec), and type II neurons with a short latency (2.76 +/- 0.20 msec) and high spontaneous firing rate (26.77 +/- 7.05/sec), probably corresponding to dopaminergic and non-dopaminergic neurons, respectively. In type I neurons, microiontophoretic application of talipexole and dopamine inhibited antidromic spike generation elicited by Acc stimulation, and talipexole-induced inhibition was antagonized by domperidone (dopamine D-2 antagonist). In type II neurons, however, the antidromic spikes were not affected by either talipexole or dopamine. Furthermore, spontaneous firing was also inhibited by iontophoretically applied talipexole and dopamine in most type I neurons, but rarely affected by either drug. Inhibitory effects of talipexole were antagonized by domperidone. These results suggest that talipexole acts on dopamine D-2 receptors, thereby inhibiting the dopaminergic neurons in the VTA.     

Sabretoothed carnivores and the killing of large prey

Sabre-like canines clearly have the potential to inflict grievous wounds leading to massive blood loss and rapid death. Hypotheses concerning sabretooth killing modes include attack to soft parts such as the belly or throat, where biting deep is essential to generate strikes reaching major blood vessels. Sabretoothed carnivorans are widely interpreted as hunters of larger and more powerful prey than that of their present-day nonsabretoothed relatives. However, the precise functional advantage of the sabretooth bite, particularly in relation to prey size, is unknown. Here, we present a new point-to-point bite model and show that, for sabretooths, depth of the killing bite decreases dramatically with increasing prey size. The extended gape of sabretooths only results in considerable increase in bite depth when biting into prey with a radius of less than ～10 cm. For sabretooths, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed. The development of the sabretooth condition appears to represent a shift in function and killing behaviour, rather than one in predator-prey relations. Furthermore, our results demonstrate how sabretoothed carnivorans are likely to have evolved along a functionally continuous trajectory: beginning as an extension of a jaw-powered killing bite, as adopted by present-day pantherine cats, followed by neck-powered biting and thereafter shifting to neck-powered shear-biting. We anticipate this new insight to be a starting point for detailed study of the evolution of pathways that encompass extreme specialisation, for example, understanding how neck-powered biting shifts into shear-biting and its significance for predator-prey interactions. We also expect that our model for point-to-point biting and bite depth estimations will yield new insights into the behaviours of a broad range of extinct predators including therocephalians (gorgonopsian + cynodont, sabretoothed mammal-like reptiles), sauropterygians (marine reptiles) and theropod dinosaurs.     

The interaction of taste and heat on the biting response of the tsetse fly Glossina fuscipes fuscipes

Abstract.Tsetse flies probe more on a heated surface with a trace of uric acid than on one without. Uric acid is one of the components of human sweat and it elicits spike responses from taste hairs on the flies' legs. In this paper it is examined how heat from the surface and taste interact to affect the biting behaviour of Glossina fuscipes fuscipes Newstead 1910 (Diptera: Glossinidae) over successive days of food deprivation. The biting behaviour consists of bouts of probing, both ambulatory and stationary, intercalated with short hops of flight. The number of bouts increases over successive days, whereas the average bout duration does not. Although uric acid alone could not induce the flies to probe, in combination with surface heat it affected the flies greatly. Average bout duration was two‐fold that on a heated surface not treated with uric acid. The frequency of bouts was not affected by uric acid. These experiments and auxiliary ones on mechanoreceptive input and odours lead to the insight that the factors which affect biting behaviour can be viewed as a hierarchy. The hierarchy extends from those that affect the onset of biting to those that affect its course.     

D-2 receptor-mediated inhibition by a substituted quinolinone derivative, 7-[3-(4-(2,3-dimethylphenyl)piperazinyl)propoxy]-2(1H)-quinolinone (OPC-4392), of dopaminergic neurons in the ventral tegmental area

A microiontophoretic study was performed to investigate the effects of a newly synthesized quinolinone derivative, 7-[3-(4-(2,3-dimethylphenyl) piperazinyl) propoxy] 2-(1H)-quinolinone (OPC-4392), on neuronal activities of the ventral tegmental area (VTA) of rats anesthetized with chloral hydrate. The VTA neurons, which were identified by antidromic stimulation of the nucleus accumbens (Acc), were classified into type I and type II neurons according to the responses to Acc stimulation: type I neurons had a long spike latency of over 7 msec (9.63 +/- 0.25 msec), and the type II, a short latency of less than 7 msec (2.98 +/- 0.27 msec) upon Acc stimulation. In all of 11 type I neurons, iontophoretically applied OPC-4392 and dopamine inhibited the antidromic spikes elicited by Acc stimulation. This inhibition was antagonized by simultaneous application of domperidone (dopamine D-2 antagonist). However, in 16 out of 19 type II neurons the antidromic spikes were not affected by either OPC-4392 or dopamine. When the effects of iontophoretically applied OPC-4392 and dopamine on spontaneous firings were tested in 32 VTA neurons identified by Acc stimulation (including type I and type II neurons), there was a relationship between the effects of these two drugs. These results suggest that OPC-4392 acts on dopamine D-2 receptors of the dopaminergic neurons in the VTA, thereby inhibiting neuronal activity.     

Oxytocin increases VTA activation to infant and sexual stimuli in nulliparous and postpartum women

After giving birth, women typically experience decreased sexual desire and increased responsiveness to infant stimuli. These postpartum changes may be viewed as a trade-off in reproductive interests, which could be due to alterations in brain activity including areas associated with reward. The goal of this study was to describe the roles of oxytocin and parity on reward area activation in response to reproductive stimuli, specifically infant and sexual images. Because they have been shown to be associated with reward, the ventral tegmental area (VTA) and nucleus accumbens (NAc) were targeted as areas of expected alterations in activity. Oxytocin was chosen as a potential mediator of reproductive trade-offs because of its relationship to both mother–infant interactions, including breastfeeding and bonding, and sexual responses. We predicted that postpartum women would show higher reward area activation to infant stimuli and nulliparous women would show higher activation to sexual stimuli and that oxytocin would increase activation to infant stimuli in nulliparous women. To test this, we measured VTA and NAc activation using fMRI in response to infant photos, sexual photos, and neutral photos in 29 postpartum and 30 nulliparous women. Participants completed the Sexual Inhibition (SIS) and Sexual Excitation (SES) Scales and the Brief Index of Sexual Function for Women (BISF-W), which includes a sexual desire dimension, and received either oxytocin or placebo nasal spray before viewing crying and smiling infant and sexual images in an fMRI scanner. For both groups of women, intranasal oxytocin administration increased VTA activation to both crying infant and sexual images but not to smiling infant images. We found that postpartum women showed lower SES, higher SIS, and lower sexual desire compared to nulliparous women. Across parity groups, SES scores were correlated with VTA activation and subjective arousal ratings to sexual images. In postpartum women, sexual desire was positively correlated with VTA activation to sexual images and with SES. Our findings show that postpartum decreases in sexual desire may in part be mediated by VTA activation, and oxytocin increased activation of the VTA but not NAc in response to sexual and infant stimuli. Oxytocin may contribute to the altered reproductive priorities in postpartum women by increasing VTA activation to salient infant stimuli.     

Leptin receptor signaling in midbrain dopamine neurons regulates feeding

The leptin hormone is critical for normal food intake and metabolism. While leptin receptor (Lepr) function has been well studied in the hypothalamus, the functional relevance of Lepr expression in the ventral tegmental area (VTA) has not been investigated. The VTA contains dopamine neurons that are important in modulating motivated behavior, addiction, and reward. Here, we show that VTA dopamine neurons express Lepr mRNA and respond to leptin with activation of an intracellular JAK-STAT pathway and a reduction in firing rate. Direct administration of leptin to the VTA caused decreased food intake while long-term RNAi-mediated knockdown of Lepr in the VTA led to increased food intake, locomotor activity, and sensitivity to highly palatable food. These data support a critical role for VTA Lepr in regulating feeding behavior and provide functional evidence for direct action of a peripheral metabolic signal on VTA dopamine neurons.