In vitro superoxide activity in the haemolymph of the West Indian leaf cockroach,Blaberus discoidalis

The respiratory burst is an NADPH oxidase-driven reduction of molecular oxygen to superoxide, which can occur in phagocytic cells as part of an antimicrobial defence, and is well documented among the vertebrates. This paper describes a process resembling the respiratory burst, which occurs in the haemolymph and haemocytes of the cockroach, Blaberus discoidalis. The in vitro reduction of nitroblue tetrazolium by superoxide to formazan was measured spectrophotometrically in B. discoidalis haemolymph in response to various immune elicitors. Nitroblue tetrazolium reduction was partly impeded in the presence of superoxide dismutase, a specific antioxidant which converts superoxide to hydrogen peroxide, as well as by chemicals known to inhibit the respiratory burst in vertebrates (trifluoperazine, diphenylene iodonium, and N-ethylmaleimide). This suggests the generation of superoxide anions by haemolymph as part of an immune response. Furthermore, formazan staining of elicitor-treated haemocytes was observed microscopically, with less intense staining in the presence of superoxide dismutase. Finally, respiratory burst inhibitors and superoxide dismutase enhanced the growth of E. coli incubated in whole haemolymph, implying a role for haemolymph-derived superoxide in antibacterial defence.     

Brood defence and parental roles in a biparental cichlid fishLamprologus toae in Lake Tanganyika

Brood defence of a cichlid fish,Lamprologus toae, was investigated in its natural habitat in Lake Tanganyika. Both parents guarding a brood attacked both conspecific and heterospecific intruder fishes at different locations. The heterospecific intruder fishes could be classified into three groups on the basis of the locations at which the attacks against each species took place. The distinction of groups by the parents seemed to be primarily based on food habits and feeding behaviour of the intruder fishes. The piscivorous species which were more dangerous for the brood were attacked by both parents at more distant locations from the brood. Parental defence of breeding territory changed with the development of the young. The frequency of attacks against each group decreased after the young reached the size too large for the fishes of the group to prey on. Division of labour in the territorial defence was recognized between male and female. The male parent mainly defended the peripheral region of the territory and the female parent defended the inner region. Significance of the selective attack against intruders and the division of labour between the two sexes in brood defence is discussed.     

The social context of cannibalism in migratory bands of the Mormon cricket

Cannibalism has been shown to be important to the collective motion of mass migratory bands of insects, such as locusts and Mormon crickets. These mobile groups consist of millions of individuals and are highly destructive to vegetation. Individuals move in response to attacks from approaching conspecifics and bite those ahead, resulting in further movement and encounters with others. Despite the importance of cannibalism, the way in which individuals make attack decisions and how the social context affects these cannibalistic interactions is unknown. This can be understood by examining the decisions made by individuals in response to others. We performed a field investigation which shows that adult Mormon crickets were more likely to approach and attack a stationary cricket that was side-on to the flow than either head- or abdomen-on, suggesting that individuals could reduce their risk of an attack by aligning with neighbours. We found strong social effects on cannibalistic behaviour: encounters lasted longer, were more likely to result in an attack, and attacks were more likely to be successful if other individuals were present around a stationary individual. This local aggregation appears to be driven by positive feedback whereby the presence of individuals attracts others, which can lead to further crowding. This work improves our understanding of the local social dynamics driving migratory band formation, maintenance and movement at the population level.     

Fatal attack on an infant by an adult female tonkean macaque

We describe a fatal attack on a 10-month-old female infant by an adult female Tonkean macaque (Macaca tonkeana)in a semi-free-ranging group. During an intense conflict involving many group members, an adult female, the second most dominant in the group, attacked the infant of a lower-ranking female. The attacker remained near the victim for approximately 20 min, grabbing and biting it repeatedly, until the mother retrieved the infant. She died 2 days later. An autopsy revealed no lethal injury;the main cause of death was starvation or dehydration or both. We discuss social conditions under which a fatal attack by an adult female might occur.     

Darwinian balancing selection: Predation counters sexual selection in a wild insect

The potential viability costs of sexually selected traits are central to hypotheses about the evolution of exaggerated traits. Estimates of these costs in nature can come from selection analyses using multiple components of fitness during the same time frame. For a population of tree crickets (Oecanthus nigricornis: Gryllidae), we analyzed viability and sexual selection on male traits by comparing Oecanthus prey of a solitary wasp to those that survived, and comparing mating individuals to solitary males. We measured forewing width (sexually size dimorphic and used for singing), head width, pronotum length, and size of hind jumping legs as potential targets of selection. Supporting the hypothesis that sexually selected traits have viability costs, we found that significant directional sexual selection for wider heads was opposed by significant viability selection for narrower heads. Nonlinear selection revealed that individuals with wide heads and small legs were most attractive, but individuals with narrow heads, large legs, and intermediate pronotum length were most likely to survive. Successful mating may put males at greater risk of predation, especially if copulation per se is risky. Such balancing selection in tree crickets may have constrained the evolution of sexual dimorphism in head size—a condition seen in other gryllids and orthopterans.     

Do territorial and non‐breeding Australian Magpies Gymnorhina tibicen influence the local movements of rural birds in New Zealand?

Australian Magpies Gymnorhina tibicen sometimes attack and kill other birds in New Zealand. Here we assess how Australian Magpies influence the local distribution of other birds in New Zealand and identify the members of an Australian Magpie population that display the most agonistic acts. We conducted regular observations on six territorial breeding groups and three non‐breeding flocks of Australian Magpies for 1 year to determine (1) if other birds avoid flying or foraging close to Australian Magpies, (2) the proportion of passing birds that are attacked and (3) which social subunits of the Australian Magpie population are most aggressive. In comparison with adjacent Magpie‐free control areas, significantly fewer birds of a range of species (e.g. Common Blackbird Turdus merula, Skylark Alauda arvensis, Yellowhammer Emberiza citrinella) foraged close (i.e. ≤ 50 m) to both territorial breeding groups and non‐breeding Australian Magpie flocks; fewer birds were also recorded flying near (i.e. ≤ 50 m) territorial breeding groups but not non‐breeding flocks. Excluding Australasian Harriers (Circus approximans: see below), only 8% of birds recorded within 50 m of territorial breeding groups were observed being attacked. Attacks were most frequent when numerous birds occurred near Australian Magpies and species recorded in the highest frequencies were generally attacked most. Territorial breeding groups attacked 39% of passing Australasian Harriers. All attacks consisted of the victim being swooped at or chased; no physical contact was ever observed. Both adult male and female breeding Australian Magpies were seen attacking other birds; juveniles in breeding groups sometimes supported adults but never initiated attacks. Australian Magpies in non‐breeding flocks were not seen attacking other birds, except Australasian Harriers (attacked in 17% of appearances). Our results suggest that some birds avoid foraging and/or flying close to Australian Magpies because they are sometimes chased by breeding adults of both sexes; however, the proportion of passing birds actually attacked was small. The numerous published observations of Australian Magpie attacks are apparently biased heavily towards sensational events that are rare. Possible reasons why Australian Magpies attack other birds are discussed.     

Effectiveness of the defence mechanism of the turnip sawfly, Athalia rosae (Hymenoptera: Tenthredinidae), against predation by lizards

The turnip sawfly, Athalia rosae Linnaeus, is a pest on cruciferous crops. Larvae sequester secondary plant compounds, namely glucosinolates, in their haemolymph. When attacked, their integument is easily disrupted and a droplet of haemolymph is exuded ('easy bleeding'). This has been shown to be an effective, chemical-based, defence against invertebrate predators. The efficiency of this proposed defence was tested against a vertebrate predator, using groups of the iguanid lizard Anolis carolinensis Voigt as a model predator. Caterpillars of Pieris rapae Linnaeus and Pieris brassicae Linnaeus served as control prey species that do not sequester glucosinolates. Lizards attacked far fewer sawfly larvae than pierid caterpillars. Several of the sawfly larvae were rejected after an initial attack, demonstrating unpalatability to the lizards, while the Pieris larvae were not rejected. However, P. rapae larvae topically treated with extracts of haemolymph of A. rosae had no deterrent effect on the lizards and no avoidance learning occurred over a period of two weeks. Adult sawflies do not easy bleed but have glucosinolates carried over from the larval stage. Lizards attacked them at a higher rate than larvae and they were never rejected. The results suggest that for the defensive effectiveness of the pest sawfly species against vertebrates the chemical cue is not necessarily sufficient. Movement and colour may be important additional factors triggering the behaviour of vertebrate predators.     

Predator responses to novel haemolymph defences of western corn rootworm (Diabrotica virgifera) larvae

Many herbivorous arthropods use defensive chemistry to discourage predators from attacking. This chemistry relies on the ability of predators to rapidly learn to recognize and avoid offensive stimuli. Western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), employs multifaceted chemical defences in its haemolymph, which may contribute significantly to its success as a major economic pest. Here, we test the hypothesis that agrobiont predators can rapidly learn to recognize and avoid WCR larvae, and will thereby reduce their contribution to WCR suppression. In controlled feeding assays, the effectiveness of WCR haemolymph defences varied across three predator taxa (crickets, centipedes, and ants). Centipedes (Chilopoda: Lithobiidae) were minimally affected by WCR defences, but crickets [Gryllus pennsylvanicus Burmeister (Orthoptera: Gryllidae)] spent less time feeding on WCR than on an undefended control prey, house fly maggots. However, we uncovered no evidence indicating that experienced crickets rapidly learn to avoid WCR larvae, indicating that haemolymph defences offer few, if any, survival benefits for WCR. Colonies of ants [Lasius neoniger Emery (Hymenoptera: Formicidae)] switched from low worker participation in initial attacks on WCR to higher worker participation in subsequent attacks, indicating an attempt to overcome, rather than avoid, WCR haemolymph defences. These results suggest that a diverse assemblage of natural enemies will show a diverse array of behavioural responses to toxic pest prey, and highlight the importance of behavioural diversity in driving the function of natural enemy assemblages.     

Interaction of a solitary larval endoparasitoid, Microplitis mediator, with its host, Mamestra brassicae: host acceptance and host suitability

Abstract:  Microplitis mediator (Haliday) (Hym., Braconidae) is an important parasitoid of early instar larvae of the European cabbage moth, Mamestra brassicae L. (Lep., Noctuidae). In the laboratory, we examined attack responses of female M. mediator to the first three larval instars of M. brassicae . Females were presented with M. brassicae larvae either one individual at a time in a no-choice experiment, or three individuals, one from each instar, simultaneously in a choice experiment. Whether or not there was choice, naïve female parasitoids attacked a high proportion of larvae and did not discriminate among instars. In the no-choice experiment, attacked larvae were reared, and parasitoid cocoons were produced from about 76% of larvae attacked as first and second instars, but from only 19% of larvae attacked as third instars. Dissections of attacked larvae from the choice experiment showed that about 79% of attacks on first and second instars resulted in oviposition compared with only 49% for third instars. When given choice, frequency and number of attacks on first instar larvae increased with increasing parasitoid experience. Our results suggest that first and second instar larvae of M. brassicae are suitable hosts for M. mediator , but that third instar larvae are suboptimal both because oviposition attempts were frequently unsuccessful and because immature parasitoids failed to complete development. Nevertheless, naïve attacking parasitoids exhibited minimal discrimination among instars, although experienced parasitoids most frequently attacked first instar larvae. The host selection behaviour of M. mediator is discussed in the context of optimal foraging theory and implications for biological control.     

Induced defence reaction in Scots pine following stem attacks by Tomicus piniperda

The induced defence reaction of Scots pine Pinus sylvestris to stem attacks by the common pine shoot beetle, Tomicus piniperda (Col, Scolytidae), was studied by inducing natural attacks on young Scots pine trees of different vigour Pruned trees were more heavily attacked by T piniperda than unpruned ones Vigorous trees successfully contained the attacking beetles within resinous lesions, whereas less vigorous trees failed to defend themselves The content of resin acids increased dramatically in the lesions on all trees, and the resin acid composition differed somewhat between some treatments Starch accumulation in the inner bark of the main stem was lower in pruned trees than in unpruned ones, and starch reserves were depleted in the most heavily attacked trees All but one of the unpruned trees survived the attack, whereas most of the severely pruned ones died following attack by beetles at densities exceeding c 300 egg galleries m⁻²     

Functional and ecological relevance of intraspecific variation in body size and shape in the lizard Podarcis melisellensis (Lacertidae)

Within populations, individual animals may vary considerably in morphology and ecology. The degree to which variation in morphology is related to ecological variation within a population remains largely unexplored. We investigated whether variation in body size and shape among sexes and age classes of the lizard Podarcis melisellensis translates in differential whole-animal performance (sprint speed, bite force), escape and prey attack behaviour in the field, microhabitat use and diet. Male and female adult lizards differed significantly in body size and head and limb proportions. These morphological differences were reflected in differences in bite strength, but not in sprint speed. Accordingly, field measurements of escape behaviour and prey attack speed did not differ between the sexes, but males ate larger, harder and faster prey than females. In addition to differences in body size, juveniles diverged from adults in relative limb and head dimensions. These shape differences may explain the relatively high sprint and bite capacities of juvenile lizards. Ontogenetic variation in morphology and performance is strongly reflected in the behaviour and ecology in the field, with juveniles differing from adults in aspects of their microhabitat use, escape behaviour and diet.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 251–264.     

Attacks on humans by the piranha Serrasalmus rhombeus in Suriname

Piranhas have a reputation of being man‐eating fishes, notwithstanding the absence of well‐documented records of piranha attacks on human beings. Three sites in Suriname where piranha attacks on bathers have taken place are discussed. In two isolated villages on the Wayombo River, most victims were children. In one village, 30 piranha attacks occurred in a period of 12 years, bites were mostly on the feet, and injuries were relatively harmless. In the second village, attacks occurred in a period of 7 years, and injuries were more serious, including the loss of digits and large and deep wounds in legs, arms and trunk. Two victims were attacked by several piranhas simultaneously. At the third site, a recreation park on the Suriname River, most attacks involved a single bite on the feet and victims were able to walk back to the beach without being attacked by other piranhas. Piranha attacks on humans did not result in deaths. The recovery of a toe phalange (Wayombo River) and a piece of flesh including a nail (Suriname River) from the stomach of two piranhas identified the fish responsible for the attacks as Serrasalmus rhombeus. Attacks on humans by S. rhombeus were associated with high age 0+ piranha densities in the dry season, high human prey densities, commotion in the water by humans, and spillage of food, fish offal or blood in the water.     

Wolf or dog? Genetic identification of predators from saliva collected around bite wounds on prey

Wolf predation on livestock is a management problem in many areas and is often used to justify control measures against the wolves. However, wolves coexist with dogs across their range, and dogs could be responsible for attacks blamed on wolves. In this study we evaluate the possibility of obtaining sufficient DNA for species identification of the predator from saliva remaining close to bite wounds following a canid attack. Predator DNA of reasonably high quality was successfully extracted from bite wounds on two sheep that had been attacked on a farm and were genotyped using six informative microsatellite markers. A single consensus genotype could be constructed from the bite wounds of both sheep which we compared to genotypes obtained from Scandinavian wolves and dogs. The results clearly showed that the saliva sampled originated from a single dog. This report thus demonstrates the feasibility of predator species identification from bite wounds and also illustrates that it can not be taken for granted that wolves are responsible for canid livestock kills.     

Attacks on neonates by a male mangabey (Cercocebus atys)

Aggressive behavior by an adult male toward selected infants and their mothers was observed during a long-term study of reproduction in a captive social group of sooty mangabeys (Cercocebus atys). The highest-ranking adult male in this group was observed to attack and bite three neonates out of a total of 13 infants born in 1982. All three attacks were directed attacks in which infants were grabbed from their mothers and bitten in the head. The first infant was fatally injured; the other two probably would have sustained fatal wounds had the male's canines not been blunted beforehand and had observers not intervened. The attacks were preceded by a pattern in which the male persistently stalked or chased the mother-infant pairs, a behavior first observed in the hours immediately following parturition. Unlike attacks in wild baboon groups following male immigration, these attacks on infants occurred in a stable social group in which the male attacker had been a lifelong resident. This male, however, had gained alpha rank only 3 months before attacking the first infant. These attacks, in the context of other evidence of aggression and wounding, are discussed relative to current models of infanticide in primates.     

Vigilance during food handling by Oystercatchers Haematopus ostralegus reduces the chances of losing prey to kleptoparasites

Oystercatchers Haematopus ostralegus periodically pause while handling mussels Mytilus edulis to make visual scans. This paper presents evidence that scanning is associated with the high incidence of intra-specific food stealing among mussel-eating Oystercatchers. Scanning increased in frequency as bird density - and the risk of being attacked for mussels increased and the duration of attacks decreased. Additionally, among a sample of individually marked adults, the aggressive dominant birds spent half as much time scanning as the less aggressive subdominants and were also less likely to be attacked. Whereas detecting an attack made no difference to the success with which the dominants defended their mussels, subdominants increased their chances of retaining the mussel if they detected and carried the mussel away from the approaching attacker. The extra time which the less aggressive birds spent in vigilance seems best understood as a tactic for reducing food loss to kleptoparasites.     

Predation on giant flying squirrels (Petaurista philippensis) by black crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Yunnan, China

Predation on vertebrates is infrequent in gibbons. In a 14-month field study of the central Yunnan black crested gibbon (Nomascus concolor jingdongensis) at Mt. Wuliang, Yunnan, China, we observed gibbons attacking, killing and eating giant flying squirrels (Petaurista philippensis). During 845 h of observation on one study group, the gibbons attacked giant flying squirrels 11 times, and succeeded in 4 cases. Although all members of the group attempted to attack the squirrels, all four successful attacks were made by the same adult female. The victims were infants in three cases and a juvenile or sub-adult in one case. Black crested gibbons also attacked adult giant flying squirrels by grabbing their long tails and throwing them from the canopy, but they failed to catch or kill the prey in three cases observed. Passive meat sharing occurred in three out of four successful cases. Besides hunting giant flying squirrels, the black crested gibbons also ate eggs or chicks in two birds’ nests and one lizard.     

Spatial consequences of aggressive behaviour in flocks of oystercatchers, Haematopus ostralegus L.

Oystercatchers were distributed non-randomly on mussel-beds in winter; the loose foraging flocks showed a ‘spaced-out gregariousness”. Aggressive defence of personal space within the flock was evidently not responsible for this spacing, as most attacks were not directed against birds unusually close to aggressors. Mutual avoidance, rather than overt aggression, apparently maintained the observed non-random spacing. Oystercatchers seemed to attack others in order to steal newly-opened mussels, but the likelihood of successfully gaining an illicit mussel in this way declined as the initial distance between attacker and victim increased. In this situation, the risk of falling victim to food theft may make avoidance of conspecifics advantageous.     

Topical application of Pya-AKH stimulates lipid mobilization and locomotion in the flightless bug, Pyrrhocoris apterus (L.) (Heteroptera)

Abstract Two different methods of applying Pya -AKH to long-winged (macropterous) females of the firebug, Pyrrhocoris apterus (Linnaeus) (Heteroptera) were compared: both injection and topical application increased the levels of lipids in the haemolymph and stimulated locomotor activity. Lipid mobilization was maximal when 10 pmol was applied by injection or 40–100 pmol by topical application, with the first significant responses occurring 1.5 h after injection and 2 h after topical application. The highest elevations of lipid concentration in the haemolymph were comparable between the treatments, i.e. 14.36 ± 3.59 mg/mL for injection and 14.43 ± 4.07 mg/mL for topical application. However, these maximal elevations were achieved at different times: 3 h after the injection and 7 h after the topical application.
Injection of 10 and 40 pmol of Pya -AKH stimulated locomotor activity with maximal activity 3 h later but, surprisingly, injection of 80 pmol showed no effect initially and than a slight inhibitory effect after 6–8 h.
Increased locomotor activity was found after topical application of Pya -AKH, but the response was lower than after injection and appeared later, 5–9 h after the hormone application. In addition, the greatest increase in walking activity required topical application of 300 pmol and was still less dramatic than the response to injection. The stimulatory effect of Pya -AKH on locomotion was positively correlated with its effect on lipid mobilization only for injection of the hormone. It is argued that a stress caused by injection could play a role in the appearance of the complex response to adipokinetic hormone.     

Effect of microsporidian infection in Lacanobia oleracea (Lep., Noctuidae) on prey selection and consumption by the spined soldier bug Podisus maculiventris (Het., Pentatomidae)

Abstract:  The predatory behaviour of Podisus maculiventris was investigated when this bug was presented with Lacanobia oleracea larvae infected with the microsporidian pathogen Vairimorpha necatrix . In choice tests, adult predatory bugs attacked V. necatrix -infected L. oleracea prey in similar numbers to uninfected larvae. Exposure to infected prey during nymphal development increased the rate at which adult bugs attacked diseased L. oleracea larvae. Fifth instar P. maculiventris nymphs, however, attacked infected prey in the majority of cases (>80% of occasions). Consumption of healthy and infected prey was measured for both adult and nymphal bugs. Over the course of 1 week, the mean number of V. necatrix -infected prey eaten by P. maculiventris adults (7.0 ± 0.82) was approximately twice the number of uninfected prey consumed (3.8 ± 0.42). Similarly, the number of prey larvae attacked by the bug over the course of the final nymphal stadium was also increased, with 2.9 ± 0.42 uninfected larvae eaten as opposed to 4.9 ± 0.27 V. necatrix -infected prey. However, small-scale investigations into the rate of P. maculiventris reduced small populations of L. oleracea indicated that the combination of the predator and pathogen would produce, at best, an additive effect.     

Consequences for a specialist insect and its parasitoid of the response of Allium porrum to conspecific herbivore attack

Abstract.  Recent studies on the leek Allium porrum L. demonstrate that a sharp increase in the release of volatile and nonvolatile sulphur compounds occurs in response to attack by the specialist phytophage, the leek moth Acrolepiopsis assectella (Zeller). The consequences of that response on the developmental capacity and behaviour of the leek moth and on the host-searching behaviour of the parasitoid hymenoptera Diadromus pulchellus Wesmael have been studied. No immediate adverse effect on larval development is seen, but the duration of male development is significantly longer. In addition, an almost 20% decrease is observed in the number of oocytes produced by adult females that developed on attack-damaged leek plants. Leek moths do not avoid damaged plants systematically. On attacked plants, larvae tend to consume more and females to lay more eggs, although the latter tendency disappears after intensive attack. Concerning host-searching by D. pulchellus , the data indicate that females make use of the induced leek response. Parasitoids are attracted more strongly to attacked plants than to undamaged plants and mechanically damaged plants. The results of this study in a tritrophic system involving a biannual plant suggest a complex defence system combining direct and indirect mechanisms. Sulphur compounds may act by reducing second-generation pests, thereby preventing the specialist insect population from exploding at the expense of the leek.