Predation by polyphagous carabid beetles on eggs of a pest slug: Potential implications of climate change

Harpalus rufipes and Poecilus cupreus are two widespread polyphagous carabids which are known to destroy eggs of the pest slug Deroceras reticulatum in the laboratory. To examine the effect of temperature on the predation of the eggs of D. reticulatum by H. rufipes and P. cupreus, a laboratory experiment with different temperatures and a semi‐field experiment including simulated warming were performed. In both experiments, H. rufipes killed more eggs than P. cupreus, and the predatory activity of the former increased significantly with increasing temperature. To our knowledge, this is the first study on predatory activity of polyphagous carabids on the eggs of a pest slug performed under a climate warming scenario. Results suggest that biological pest control performed by polyphagous carabids such as H. rufipes upon pest slugs may be enhanced under predicted climate warming conditions.     

Millipedes vs. pathogens: Defensive secretions of some julids (Diplopoda: Julida) as potential antimicrobial agents

In the light of growing interest in discovering new sources of natural antimicrobial agents, we extracted and tested the efficiency of julid defensive secretions in comparison with commercially used antibiotic and antimycotics. This work involved chemical characterization of the defensive secretions of Cylindroiulus boleti (C. L. Koch, 1847), Megaphyllum bosniense (Verhoeff, 1897) and M. unilineatum (C. L. Koch, 1838), as well as in vitro evaluation of their antimicrobial activity against 11 bacteria, one yeast and eight filamentous fungi. Compounds of the analysed defensive secretions included p‐benzoquinones, alkyl esters of fatty acids and ketones. Ketones were recorded for the first time in the order Julida, and they were detected in secretions of both Megaphyllum species. All three analysed defensive secretions showed antibacterial and antifungal potential against all of the tested pathogens. Staphylococcus aureus proved to be the most sensitive bacterial strain to all analysed secretions. Also, defensive secretion of M. unilineatum showed significant antibacterial potential against Bacillus subtilis. The most resistant bacterial strains in this study were Escherichia coli, Erwinia persicina and Pseudomonas syringae pv. tomato. Analysed defensive secretions achieved the strongest antifungal activity against Aspergillus parasiticus (secretions of all three millipede species), Penicillium griseofulvum (secretions of C. boleti and M. bosniense) and Cladosporium oxysporum (secretion of M. unilineatum). The most resistant mycromycetes were A. niger (to all tested defensive secretions), A. flavus (to secretion of M. unilineatum) and P. lanosum (to secretions of C. boleti and M. bosniense). Our results showed a generally lower level of activity compared to antibiotic and a significantly higher level compared to antimycotics. The results of this study elucidate and open opportunities for further research in the field of millipede chemical ecology.     

Mechanisms of temporary adhesion in benthic animals

Adhesive systems are ubiquitous in benthic animals and play a key role in diverse functions such as locomotion, food capture, mating, burrow building, and defence. For benthic animals that release adhesives, surface and material properties and external morphology have received little attention compared to the biochemical content of the adhesives. We address temporary adhesion of benthic animals from the following three structural levels: (a) the biochemical content of the adhesive secretions, (b) the micro‐ and mesoscopic surface geometry and material properties of the adhesive organs, and (c) the macroscopic external morphology of the adhesive organs. We show that temporary adhesion of benthic animals is affected by three structural levels: the adhesive secretions provide binding to the substratum at a molecular scale, whereas surface geometry and external morphology increase the contact area with the irregular and unpredictable profile of the substratum from micro‐ to macroscales. The biochemical content of the adhesive secretions differs between abiotic and biotic substrata. The biochemistry of the adhesives suitable for biotic substrata differentiates further according to whether adhesion must be activated quickly (e.g. as a defensive mechanism) or more slowly (e.g. during adhesion of parasites). De‐adhesion is controlled by additional secretions, enzymes, or mechanically. Due to deformability, the adhesive organs achieve intimate contact by adapting their surface profile to the roughness of the substratum. Surface projections, namely cilia, cuticular villi, papillae, and papulae increase the contact area or penetrate through the secreted adhesive to provide direct contact with the substratum. We expect that the same three structural levels investigated here will also affect the performance of artificial adhesive systems.     

Light dependency of life trails,reproduction, locomotion,and predation in the polyphagous ladybird Hippodamia variegata

Light is regarded a key environmental cue influencing biological, physiological, and behavioral characteristics in insects. We compared the development, reproduction, locomotion, and predation ability of the predatory ladybird Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae) under various photoperiods, light intensities, and light wavelengths. The results indicated long daylight, high light intensity, and particular colors light (blue, green, and yellow) could benefit H. variegata especially in shortening the period of immature development, increasing mating frequency (shorter mating and pre‐oviposition periods), higher fecundity, and a higher proportion of eggs hatched. Average locomotion speed and prey consumption rate of H. variegata increased with prolonged day length and increased light intensity. However, very high intensity of light could inhibit predation rates. Furthermore, green and yellow wavelength conditions increased locomotion speed of H. variegata, and the number of prey consumed increased with increased wavelength. The present study not only revealed significant influences of light conditions on the development and fertility of H. variegata, it also provided sufficient empirical data to improve the efficiency of mass rearing and field releases of this predatory ladybird by regulation of light conditions during biological control applications.     

Predation behaviour of land planarians

Predatory behaviour of land planarians is seldom observed or reported. Aspects reported are (1) finding prey; (2) attack behaviour; (3) capture using adhesive mucus, pharyngeal action, poisonous secretions, physical embrace; (4) feeding by extension of pharynx, releasing copious digestive fluid. The species Bipalium kewense, B. adventitium and B. pennsylvanicum attack earthworms, immobilizing them by physical holding, digesting by pharyngeal secretions and then ingesting the treated tissue. Group attacks on giant African land snails involving chemotactic tracking, occur in Platydemus manokwari and Endeavouria septemlineata. Specialized capture methods are used by some species; Rhynchodemus sylvaticus uses an expanded cephalic hood to capture small insects and in Africa, termites are captured by the elongated anterior of Microplana termitophaga as planarians wait within the colony air shaft openings to ensnare the workers in sticky mucus. The result of extensive predation by land planarians may seriously reduce the prey, e.g., providing effective population control of giant land snails by introduced Platydemus manokwari, or causing serious depletion of desirable earthworm populations by the exotic Artioposthia triangulata in North Ireland.     

The Lactoperoxidase System: a Natural Biochemical Biocontrol Agent for Pre‐ and Postharvest Applications

Controlling pests in pre‐ and postharvest crops using natural and low‐impact products is a major challenge. The lactoperoxidase system is an enzymatic system that exists in all external secretions in mammals and is part of the non‐immune system. We tested its efficacy in in vitro microplates on Phytophthora infestans, Penicillium digitatum, Penicillium italicum, Penicillium expansum and Botrytis cinerea to determine the most suitable concentrations for use. Then, we verified its efficacy in planta under controlled conditions. Solutions prepared with 5.4 mm iodide and 1.2 mm thiocyanate and diluted threefold inhibited pathogen growth in vitro by 63–100%. Twofold‐diluted solutions protected potato plants against P. infestans by 60–74% under controlled conditions. Undiluted solution inhibited orange's and apple's postharvest pathogens in curative application with efficacy levels ranging between 84 and 95% in orange and between 63 and 74% in apple. 1.5‐fold concentrated solutions inhibited postharvest pathogens of apple in curative application with efficacy levels ranging between 84 and 92%. Our results also show that the oxidative stress response of fruit following wounding could interfere with ion efficiency. Our tests demonstrate for the first time that this biochemical method is as efficient as a conventional synthetic chemical method under controlled conditions.     

Effects of metaldehyde and methiocarb on feeding preferences and survival of a slug predator (Pterostichus melanarius (F.): Carabidae,Pterostichini)

The potential for reducing slug populations in crops through predation by generalist carabid beetles is well documented. However, few studies have considered interactions between biological and chemical control agents of slugs. Laboratory assays supported previous findings that the consumption of metaldehyde by slugs (Deroceras reticulatum) leads to increased duration of feeding bouts by carabid beetles (such as Pterostichini) on sub‐lethally affected individuals. However, a similar effect was not found for Pterostichus melanarius exposed to slugs fed on the other widely applied pelleted molluscicide formulation (methiocarb). Examination of beetle survival after consumption of slugs containing molluscicides demonstrated the strong biocidal properties of methiocarb, whereas metaldehyde consumption (ingested through slug predation) did not differ from control slugs killed by freezing. Beetle avoidance of slugs containing a more toxic molluscicide compound and the interaction between slug mucus production and beetle attack rates are discussed.     

Tracking predator density dependence and subterranean predation by carabid larvae on slugs using monoclonal antibodies

1. Subterranean carabid larvae are more numerous than surface‐active adults, yet very little is known about their ecological significance, dietary preferences or ability to regulate populations of prey species, particularly pests. Part of the reason for this is that predator–prey interactions beneath the soil are almost impossible to observe. 2. Extensive field studies have shown that adult Pterostichus melanarius (Illiger) can affect the temporal and spatial dynamics of their slug prey. However, if larvae too are feeding on slugs, this could radically affect overall predator–prey dynamics. 3. We tested the hypotheses that P. melanarius larvae would kill and consume two slug species, Deroceras reticulatum Müller and Arion intermedius Normand, under laboratory and semi‐field conditions, and that there would be no significant difference in rates of predation on these slug species. 4. A new monoclonal antibody was developed that was capable of detecting the presence of slug proteins in the guts of P. melanarius larvae. 5. Pterostichus melanarius larvae killed both A. intermedius and D. reticulatum in the laboratory, feeding to a greater extent, and growing more rapidly, on the latter. The larvae were equally effective at reducing numbers of both slug species in a crop of wheat grown in semi‐field mini plots, but predation was affected by density‐dependent intra‐specific competition amongst the beetle larvae. 6. Future modelling of the dynamic interactions between carabids and slugs will need to take into account predation by larvae.     

Effect of adult females' predation risk on oviposition site selection in a water strider

In many egg‐laying species, females avoid ovipositing at sites where the predation risk is high. Previous studies have mainly focused on the risk for offspring. The effect of predation risk for the females has been considered in some taxa in which parents spend much time at an oviposition site for parental care or mating (e.g., birds, amphibians). In species in which females do not perform activities other than oviposition at sites, the effect of predation risk for females on oviposition site selection has been rarely investigated. We examined whether the predation risk for ovipositing females affects the decision on oviposition in the water strider Aquarius paludum insularis (Motschulsky) (Heteroptera: Gerridae). Adult A. paludum are preyed upon by a backswimmer, Notonecta triguttata (Motschulsky) (Heteroptera: Notonectidae), but N. triguttata does not prey upon eggs or early instars of A. paludum. We allowed female A. paludum to oviposit under one of three conditions: in presence of N. triguttata, in presence of its chemicals, and in absence of the predator or its cues (control). Female A. paludum less frequently oviposited in presence of N. triguttata than in its absence. Oviposition frequency did not differ between females in presence of chemicals of N. triguttata vs. those in the control. Female A. paludum recognized the predation risk upon themselves from the presence of N. triguttata and avoided ovipositing. This study is the first to directly show that the predation risk upon ovipositing females changes oviposition site selection in species in which the time spent at an oviposition site is short.     

Multiple Lines of Egg Defense in a Neotropical Arachnid with Temporary Brood Desertion

Egg predation is the one of the main costs of brood desertion in many ectothermic animals. When stressful environmental conditions constrain parental activities to only some periods of the day, the combination of physical or chemical defenses may attenuate the costs related to egg loss during periods of temporary parental absence. Females of the harvestman Neosadocus maximus periodically abandon their clutches to shelter or forage. They also cover their eggs with a hygroscopic mucus coat and seem to lose fewer eggs to predation than other syntopic harvestmen whose eggs lack the mucus coat. Using two species of N. maximus egg predators, we demonstrate that eggs whose mucus coat was experimentally removed suffered higher predation rate than eggs whose mucus coat was left intact. We argue that this mucus provides physical protection against egg predators, especially small arthropods. A similar mucus coat has independently evolved in other two clades of Neotropical harvestman in which males care for the eggs and typically leave their clutches unattended for several hours a day. We propose that the presence of multiple lines of egg defense may have evolved as a way of lowering the costs imposed by intra‐ and interspecific egg predation during periods of temporary brood desertion.     

The effect of growth media and physical treatments on the adhesion properties of canine probiotics

Aims

The manufacturing processes have been reported to influence the properties of probiotics with potential impact on health properties. The aim was to investigate the effect of different growth media and inactivation methods on the properties of canine‐originated probiotic bacteria alone and in combination mixture.

Methods and Results

Three established dog probiotics, Lactobacillus fermentum VET9A, Lactobacillus plantarum VET14A and Lactobacillus rhamnosus VET16A, and their combination mixture were evaluated for their adhesion to dog mucus. The effect of different growth media, one reflecting laboratory and the other manufacturing conditions, and inactivation methods (95°C, 80°C and UV irradiation) on the mucus adhesion of the probiotic strains was characterized. Evaluation of dog probiotics was supported by cell visualization using transmission electron microscopy (TEM). Higher adhesion percentage was reported for probiotic strains growing in laboratory rather than in manufacturing conditions (P < 0·05). Inactivation by heat (95°C, 80°C) decreased the adhesion properties when strains were cultivated in soy‐based growth media compared with those grown in MRS broth (P < 0·05). TEM observations uncovered differences in cell‐surface components in nonviable forms of probiotic strains as compared with their viable forms.

Conclusions

Manufacturing process conditions such as growth media and pretreatment methods may significantly affect the adhesive ability of the tested strains.

Significance and Impact of the Study

Growth conditions, growth media, pretreatment methods and different probiotic combinations should be carefully considered for quality control of existing probiotics and for identification of new probiotics for dogs. These may also have an impact on health benefits for the host.     

When directional selection reduces geographic variation in traits mediating species interactions

Although we often focus on the causes of geographic variation, understanding processes that act to reduce geographic variation is also important. Here, we consider a process whereby adaptive foraging across the landscape and directional selection exerted by a conifer seed predator, the common crossbill (Loxia curvirostra), potentially act to homogenize geographic variation in the defensive traits of its prey. We measured seed predation and phenotypic selection exerted by crossbills on black pine (Pinus nigra) at two sites in the Pindos Mountains, Greece. Seed predation by crossbills was over an order of magnitude higher at the site where cone scale thickness was significantly thinner, which was also the cone trait that was the target of selection at the high predation site. Additional comparisons of selection differentials demonstrate that crossbills exert selection on black pine that is consistent in form across space and time, and increases in strength with increasing seed predation. If predators distribute themselves in relation to the defensive traits of their prey and the strength of selection predators exert is proportional to the amount of predation, then predators may act to homogenize trait variation among populations of their prey in a process analogous to coevolutionary alternation with escalation.     

Sexually selected UV signals in the tropical ornate jumping spider,Cosmophasis umbratica may incur costs from predation

Sexually selected ornaments and signals are costly to maintain if they are maladaptive in nonreproductive contexts. The jumping spider Cosmophasis umbratica exhibits distinct sexual dichromatism with males displaying elaborate UV body markings that signal male quality. Female C. umbratica respond favorably to UV‐reflecting males and ignore males that have their UV masked. However, Portia labiata, a UV‐sensitive spider‐eating specialist and a natural predator of C. umbratica, is known to use UV reflectance as a cue when hunting prey. We investigated the cost of these UV signals in C. umbratica in terms of their predation risk. Under experimental conditions, three choice scenarios were presented to P. labiata individuals. Choices by P. labiata were made between male C. umbratica with and without the UV signal; a UV‐reflecting male and non‐UV‐reflecting female; and a UV‐masked male and female. The presence and absence of UV signals was manipulated using an optical filter. Portia labiata exhibited a strong bias toward UV+ individuals. These results suggest the sexually selected trait of UV reflectance increases the visibility of males to UV‐sensitive predators. The extent of this male‐specific UV signal then is potentially moderated by predation pressure. Interestingly though, P. labiata still preferred males to females irrespective of whether UV reflectance was present or not. This suggests P. labiata can switch cues when conditions to detect UV reflectance are not optimal.     

Embryonic and larval defensive responses of agile frog (Rana dalmatina) to alien crayfish

Red swamp crayfish Procambarus clarkii, a widespread invasive alien crayfish, represents a serious threat for several freshwater species, including amphibians, which are declining at a global scale. As a shared coevolutionary history is the main factor determining the emergence of antipredator responses, Anuran tadpoles may not be able to cope effectively with this introduced predator. We performed two experiments to assess agile frog's (Rana dalmatina) defensive responses to both P. clarkii and native dragonfly larvae (Anax imperator). First, we conditioned embryos (collected from two ponds 30 km away from each other) with predators’ chemical cues to explore possible variation in hatching time caused by predation risk. In the second experiment, to evaluate how predators’ diet affects tadpole behavior, we conditioned tadpoles for a 5‐week period with cues from tadpole‐fed and gammarid‐fed predators and recorded behavioral and morphological responses. Embryos did not alter hatching time in the presence of any predator cue, while tadpoles from both populations strongly reduced activity and visibility when raised in the presence of tadpole‐fed dragonfly larvae. Morphological changes were less straightforward and were induced only in one population, for which broader tails and a slight increase in body size of tadpoles exposed to tadpole‐fed predators were observed. The lack of defensive responses in crayfish‐exposed tadpoles suggests that the spreading of this invasive species in agricultural lowlands of northern Italy may represent a further threat to their conservation.     

Laboratory evaluation of predation rates of two native natural enemies on the exotic pest Bagrada hilaris

Laboratory studies were conducted to determine the consumption rates of two native predators found attacking the exotic invasive stink bug Bagrada hilaris (Burmeister) (Hempitera: Pentatomidae) in field plots in New Mexico, USA. Individual field‐collected adults of the spined soldier bug, Podisus maculiventris (Say) (Hempitera: Pentatomidae) and the soft‐winged flower beetle, Collops vittatus (Say) (Coleoptera: Melyridae), were provided daily with fixed numbers of different life stages of B. hilaris under controlled conditions. Consumption rates were recorded daily for ten consecutive days for a total of 20 adult P. maculiventris and 20 adult C. vittatus per prey life stage. For P. maculiventris, predation rates were obtained in relation to adult, third and fifth instar prey, and for C. vittatus for first, second and third instar prey. On average, predation on third and fifth instar B. hilaris nymphs by P. maculiventris was 0.6 ± 0.1 and 0.9 ± 0.1 per day respectively. Predation rates on adults were slightly higher (1.3 ± 0.1 per day), with female prey being consumed at a significantly higher rate than male prey when three mating pairs of B. hilaris were provided per day (0.8 ± 0.1 females per day vs. 0.5 ± 0.1 males per day). Collops vittatus adults provisioned daily with 20 first instar B. hilaris nymphs killed a mean total of 4.7 ± 0.4 and 9.3 ± 0.6 prey each day (for male and female beetles respectively), with only approximately half that number of prey being fully consumed. Partial consumption of prey by this species was also observed with second and third instar nymphs, but to a lesser degree. Female beetles consumed significantly more prey than did male beetles when fed first and third instar B. hilaris, but not when given second instar prey.     

Influence of light on the foraging impact of an introduced predatory cladoceran,Bythotrephes longimanus

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Do pygidial secretions of dung beetles have the potential to repel urban pest ants?

Various organisms emit malodorous secretions against competitors, and the potential use of these secretions in pest management should be investigated. For example, some ant species feed on similar resources as dung beetles, which might have led to counter chemical defences in dung beetles. We tested whether pygidial secretions of the dung beetle Canthon smaragdulus (Fabricius) (Coleoptera: Scarabaeidae, Scarabaeinae) alter the locomotor behaviour of the exotic urban pest ant Tapinoma melanocephalum (Fabricius) (Hymenoptera: Formicidae), specifically whether these secretions repel those ants. We also tested whether the disturbance in the locomotor behaviour of T. melanocephalum increases with the amount of pygidial secretion. We found that individual T. melanocephalum displayed changes in their locomotor behaviour when exposed to pygidial secretions of coupled dung beetles, single males, and single females. Additionally, the pygidial secretions from male and female dung beetles could repel ants. The change in the locomotor behaviour of T. melanocephalum increased with the amount of pygidial secretion. Our results suggest that the pygidial secretions of dung beetles have potential as a biological repellent of T. melanocephalum. Hence, pygidial secretions from dung beetles may be used in the future for the development of urban pest management strategies.     

Chemical egg defence in the large milkweed bug,Oncopeltus fasciatus,derives from maternal but not paternal diet

Many herbivorous insects sequester defensive compounds from their host‐plants and incorporate them into their eggs to protect them against predation. Here, we investigate whether transmission of cardenolides from the host‐diet to the eggs is maternal, paternal, or biparental in the large milkweed bug, Oncopeltus fasciatus (Dallas) (Hemiptera: Lygaeidae). We reared individual bugs on either milkweed seeds [MW; Asclepias syriaca L. (Apocynaceae)] that contain cardenolides, or on sunflower seeds [SF; Helianthus annuus L. (Asteraceae)] that do not contain cardenolides. We mated females and males so that all four maternal/paternal diet combinations were represented: MW/MW, MW/SF, SF/MW, and SF/SF. Using larvae of the common green lacewing, Chrysoperla (Chrysopa) carnea (Stevens) (Neuroptera: Chrysopidae), we conducted two‐choice predation trials to assess whether maternal, paternal, or biparental transmission of cardenolides into the eggs of O. fasciatus increased protection against predation. Furthermore, we used high performance liquid chromatography (HPLC) to assess putative cardenolide content of eggs from the various parental diet treatment groups. The predation trials suggested that regardless of male diet, eggs were afforded better protection when females had been raised on milkweed. However, many eggs were at least partially consumed. This suggests that although chemical defence of eggs does not guarantee protection to eggs on an individual basis, they may increase the probability that some eggs in a clutch are left intact thereby potentially conferring a fitness advantage to more offspring than if eggs are left unprotected. Based on HPLC analysis we found that maternal contribution of cardenolides was significantly greater than paternal contribution of cardenolides to the eggs, supporting the results of our predation trials that a maternal diet of milkweed makes eggs more distasteful than a paternal diet of milkweed.     

Body‐colour variation in an orb‐web spider and its effect on predation success

Animal body coloration serves several functions such as thermoregulation, camouflage, aposematism, and intraspecific communication. In some orb‐web spiders, bright and conspicuous body colours are used to attract prey. On the other hand, there are other species whose body colour does not attract prey. Using a spider species showing individual body‐colour variation, the present study aimed to determine whether or not the variation in body colour shows a correlation with predation rates. We studied the orb‐web spider (Cyclosa argenteoalba) using both field observations and T‐maze experiments, in which the prey were exposed to differently coloured spiders. Cyclosa argenteoalba has silver‐ and black‐coloured areas on its dorsal abdomen, with the ratio of these two colours varying continuously among individuals. The bright and conspicuous silver area reflects ultraviolet light. Results of both field observations and colour choice experiments using Drosophila flies as prey showed that darker spiders have a greater chance of capturing prey than silver spiders. This indicates that body‐colour variation affects predation success among individuals and that the bright silver colour does not function to attract prey in C. argenteoalba.     

Importance of trap liner adhesive selection for male moth catch (Lepidoptera: Tortricidae) with bisexual attractants

Studies compared moth captures of three pests (Lepidoptera: Tortricidae) of apple, Malus domestica Borkhausen, in delta traps using removable liners coated with either a sticky gel (SG) or a hot‐melt pressure sensitive (HMPS) adhesive. Laboratory and field studies with Cydia pomonella (L.), Choristoneura rosaceana (Harris) and Grapholita molesta (Busck) demonstrated that traps with either liner, baited with a pair of virgin females catch males, but at significantly different levels. In the field, male moth captures in traps with the HMPS liner were significantly greater than in traps with the SG liner for C. rosaceana, and G. molesta; but not for C. pomonella. Similar results were observed in laboratory studies using flight tunnels. Additional studies demonstrated that this difference in moth captures between liners was not due to levels of female mortality, but instead was correlated with the occurrence of the female's ventral abdominal surface becoming stuck in the adhesive. Studies showed that a significantly greater proportion of females of all species had their ventral abdomen stuck in the SG than HPMS adhesive on day 1, but only G. molesta and C. rosaceana on day 3. In addition, the tackiness of the two adhesives affected moth movement on the liner with males and females of all species moving farther on liners with SG than HMPS adhesive. A greater proportion of female G. molesta and C. pomonella were either stuck supined or laterally on the SG than HMPS adhesive, and females in this position captured as many males as when prone and unstuck on the liner. Our studies demonstrate that adhesives can secondarily influence male moth captures on trap liners when used with bisexual attractants, and that adhesive type should be considered when developing action thresholds.