Cantharidin world on islands: Species diversity of canthariphilous arthropods in the Izu–Ogasawara Arc

Cantharidin is a defense chemical produced by only two beetle families, Meloidae and Oedemeridae. This compound also functions as an attractant for certain groups of arthropods (canthariphilous arthropods). Cantharidin‐producing beetles and canthariphilous arthropods build a cantharidin‐mediated community, called cantharidin world. In this study, to clarify the canthariphilous arthropod community formed on small islands, the arthropods were collected by cantharidin‐baited traps and compared among the mainland, peninsula and 11 small islands of the Izu–Ogasawara Arc, Japan. Control traps without cantharidin were also used to collect non‐canthariphilous arthropods. Cantharidin‐producing beetles were distributed across the study area, but the number of species was reduced on islands. We identified 10 species of five families as canthariphilous arthropods in this study area: two species of Anthicidae and Pyrochroidae (Coleoptera), four species of Ceratopogonidae (Diptera), three species of Formicidae (Hymenoptera) and one species of Podoctidae (Opiliones). The number of canthariphilous species was not correlated with island size (area) but was negatively correlated with the distance of island from the mainland. These tendencies were also seen in non‐canthariphilous fauna. The canthariphilous arthropods increased with the number of cantharidin‐producing beetle species, but the non‐canthariphilous fauna did not. Thus, the cantharidin world on islands seems to be affected not only by the geographic characteristics of islands, particularly the degree of isolation from the mainland, but also by the diversity of cantharidin‐producing members within it.     

Posttreatment confounding in causal mediation studies: A cutting-edge problem and a novel solution via sensitivity analysis

In causal mediation studies that decompose an average treatment effect into indirect and direct effects, examples of posttreatment confounding are abundant. In the presence of treatment-by-mediator interactions, past research has generally considered it infeasible to adjust for a posttreatment confounder of the mediator–outcome relationship due to incomplete information: for any given individual, a posttreatment confounder is observed under the actual treatment condition while missing under the counterfactual treatment condition. This paper proposes a new sensitivity analysis strategy for handling posttreatment confounding and incorporates it into weighting-based causal mediation analysis. The key is to obtain the conditional distribution of the posttreatment confounder under the counterfactual treatment as a function of not only pretreatment covariates but also its counterpart under the actual treatment. The sensitivity analysis then generates a bound for the natural indirect effect and that for the natural direct effect over a plausible range of the conditional correlation between the posttreatment confounder under the actual and that under the counterfactual conditions. Implemented through either imputation or integration, the strategy is suitable for binary as well as continuous measures of posttreatment confounders. Simulation results demonstrate major strengths and potential limitations of this new solution. A reanalysis of the National Evaluation of Welfare-to-Work Strategies (NEWWS) Riverside data reveals that the initial analytic results are sensitive to omitted posttreatment confounding.     

Behavior of uncharged oximes compared to HI6 and 2-PAM in the human AChE-tabun conjugate: a molecular modeling approach

Tabun is one of the most dangerous nerve agents because it has deleterious effects like inhibition of the essential enzymes acetylcholinesterase (AChE) and butyrylcholinesterase. Some oximes such HI6 as 2-PAM are nucleophiles that are capable to reactivate inhibited human AChE under some conditions. Zwitterionic and cationic species have the best chance of productive action on inhibited AChE. However uncharged oximes can give important interaction information. In order to investigate the interaction and behavior of cationic and uncharged oximes, we performed molecular docking simulations and molecular dynamics and calculated binding energies of complexes of these compounds with human AChE. The uncharged oximes of larger structure were more susceptible to the influence of the substituents on the phosphorus atom and presented low binding energies. In contrast, HI 6 and 2-PAM showed high binding energy values with great contribution of the amino acid Asp74, demonstrating the importance of the quaternary nitrogen to the affinity and interaction of the oximes/AChE tabun-inhibited complexes.     

Assessing the effect of complex ground types on ground‐dwelling arthropod movements with video monitoring: Dealing with concealed movements under a layer of plant residues

Understanding the effect of ground types on foraging movements of ground‐dwelling arthropods is a key step to managing their spatial distribution as required for successful conservation biological control. Indeed, fine movements at the centimeter scale can strongly influence the foraging ability of pest predators. However, because radio frequency identification or harmonic tracking techniques are not yet suitable for small species and video tracking focuses on uniform and light backgrounds, foraging movements have rarely been studied in relation to ground types. We present a method to track a ground‐dwelling arthropod (the earwig Euborellia caraibea) at night, walking on two contrasted ground types: bare soil and soil partly covered with a stratum of banana plant residues allowing individuals to hide periodically. The tracking of individuals within these ground types was achieved by infrared light, tagging individuals, video treatments, and semi‐automatic cleaning of trajectories. We tested different procedures to obtain segments with identical durations to quantify speeds and sinuosities. These procedures were characterized by the junction time gap between trajectory fragments, the rediscretization time of trajectories, and whether or not to use interpolation to fill in missing points in the trajectories. Earwigs exhibited significantly slower and more sinuous movements on soil with banana plant residues than on bare soil. Long time gaps for trajectory junction, extended rediscretization times, and interpolation were complementary means to integrate concealed movements in the trajectories. The highest slowdown in plant residues was detected when the procedure could account for longer periods under the residues. These results suggest that earwigs spent a significant amount of time concealed by the residues. Additionally, the residues strongly decreased the earwigs'' movement. Since the technical solutions presented in this study are inexpensive, easy to set up, and replicate, they represent valuable contributions to the emerging field of video monitoring.     

The fluctuating world of a tundra predator guild: bottom‐up constraints overrule top‐down species interactions in winter

Global warming is predicted to change ecosystem functioning and structure in Arctic ecosystems by strengthening top‐down species interactions, i.e. predation pressure on small herbivores and interference between predators. Yet, previous research is biased towards the summer season. Due to greater abiotic constraints, Arctic ecosystem characteristics might be more pronounced in winter. Here we test the hypothesis that top‐down species interactions prevail over bottom‐up effects in Scandinavian mountain tundra (Northern Sweden) where effects of climate warming have been observed and top‐down interactions are expected to strengthen. But we test this ‘a priori’ hypothesis in winter and throughout the 3–4 yr rodent cycle, which imposes additional pulsed resource constraints. We used snowtracking data recorded in 12 winters (2004–2015) to analyse the spatial patterns of a tundra predator guild (arctic fox Vulpes lagopus, red fox Vulpes vulpes, wolverine Gulo gulo) and small prey (ptarmigan, Lagopus spp). The a priori top‐down hypothesis was then tested through structural equation modelling, for each phase of the rodent cycle. There was weak support for this hypothesis, with top‐down effects only discerned on arctic fox (weakly, by wolverine) and ptarmigan (by arctic fox) at intermediate and high rodent availability respectively. Overall, bottom‐up constraints appeared more influential on the winter community structure. Cold specialist predators (arctic fox and wolverine) showed variable landscape associations, while the boreal predator (red fox) appeared strongly dependent on productive habitats and ptarmigan abundance. Thus, we suggest that the unpredictability of food resources determines the winter ecology of the cold specialist predators, while the boreal predator relies on resource‐rich habitats. The constraints imposed by winters and temporary resource lows should therefore counteract productivity‐driven ecosystem change and have a stabilising effect on community structure. Hence, the interplay between summer and winter conditions should determine the rate of Arctic ecosystem change in the context of global warming.     

Inhibition of development of anti-predator morphology in the small cladoceran Bosmina by an insecticide: impact of an anthropogenic chemical on prey–predator interactions

1. The combined effect of the insecticide carbaryl and the predator (Leptodora kindtii) kairomone was assessed on the development of protuberant morphology in the small cladoceran Bosmina fatalis, a feature which evolved originally as a response to the kairomone. The experiment showed that Bosmina changed its morphology in response to the kairomone, but development was inhibited by carbaryl at a sub‐lethal concentration even in the presence of the kairomone. At the same time, reduction of fecundity was observed in animals exposed to carbaryl. 2. A short‐term feeding experiment (B. fatalis versus Leptodora) indicated that such low concentrations of the insecticide had no impact on predation by Leptodora. Thus, it is suggested that the inhibition of development of anti‐predatory defences in Bosmina can increase its vulnerability to predation. 3. Such disturbance of chemical communication by the insecticide reduces the individual survival rate of prey Bosmina in the environment with high predator density. On the other hand, reduction of fecundity may result in decreased population growth rate of animals. 4. The impact of the insecticide on the anti‐predator morphology in Bosmina (inhibition) was opposite to that in Daphnia (enhancement). This suggests that biochemical induction processes in the development of anti‐predatory morphology are evolutionally different between Daphnia and Bosmina.     

The role of the oximes HI-6 and HS-6 inside human acetylcholinesterase inhibited with nerve agents: a computational study

The oximes 4-carbamoyl-1-[({2-[(E)-(hydroxyimino) methyl] pyridinium-1-yl} methoxy) methyl] pyridinium (known as HI-6) and 3-carbamoyl-1-[({2-[(E)-(hydroxyimino) methyl] pyridinium-1-yl} methoxy) methyl] pyridinium (known as HS-6) are isomers differing from each other only by the position of the carbamoyl group on the pyridine ring. However, this slight difference was verified to be responsible for big differences in the percentual of reactivation of acetylcholinesterase (AChE) inhibited by the nerve agents tabun, sarin, cyclosarin, and VX. In order to try to find out the reason for this, a computational study involving molecular docking, molecular dynamics, and binding energies calculations, was performed on the binding modes of HI-6 and HS-6 on human AChE (HssAChE) inhibited by those nerve agents.     

How cricket frog females deal with a noisy world: habitat-related differences in auditory tuning

Cricket frogs (Acris crepitans) occupy a variety of acousticallydifferent habitats ranging from pine forest to open grassland.There is geographic variation in their calls and the tuningof their basilar papilla (BP) correlated with habitat. Here,we characterize the spectral content of environmental noisefrom two habitats, one a pine forest (Stengl) and one a grassland(Gill) habitat. We then used rounded exponential filter functionsbased on the mean tuning of auditory fibers in Stengl and Gillfemales to model the BP tuning characteristics of an averagefemale from the two cricket frog populations occupying thosehabitats to compare their ability to filter out environmentalnoise. Noise recordings were made at both sites from 1800 to2400 h on multiple nights throughout a breeding season (Marchthrough early August). Noise spectra were similar at both sites.Cross-correlation analyses of the sampled noise indicated thatnoise spectra were consistent throughout the night and variedlittle over the season other than during the month of May. Themodel auditory filter simulating an average Stengl female wassignificantly better than one simulating an average Gill femaleat filtering environmental noise at both sites. Previous workhad shown that cricket frog calls suffered greater attenuationand degradation in the Stengl site than the Gill site but thatthe male calls from Stengl frogs suffered less attenuation andless degradation than Gill calls during transmission throughboth habitats. These new results demonstrate that frogs fromthe more acoustically challenging Stengl habitat have enhancedboth the sender and receiver portions of their communicationsystem, evolving calls that transmit better and auditory filtersthat better eliminate noise.     

The investigation of interactions of kappa-Hefutoxin1 with the voltage-gated potassium channels: a computational simulation

Kappa-Hefutoxin1 is a K(+) channel-blocking toxin from the scorpion Heterometrus fluvipes. It is a 22-residue protein that adapts a novel fold of two parallel helices linked by two disulfide bridges without beta-sheets. Recognition of interactions of kappa-Hefutoxin1 with the voltage-gated potassium channels, Kv1.1, Kv1.2, and Kv1.3, was studied by 3D-Dock software package. All structures of kappa-Hefutoxin1 were considered during the simulations, which indicated that even small changes in the structure of kappa-Hefutoxin1 considerably affected both the recognition and the binding between kappa-Hefutoxin1 and the Kv1 channels. kappa-Hefutoxin1 is located around the extracellular part of the Kv1 channels, making contacts with its helices. Lys 19, Tyr 5, Arg 6, Trp 9, or Arg 10 in the toxin and residues Asp 402, His 404, Thr 407,Gly 401, and Asp 386 in each subunit of the Kv potassium channel are the key residues for the toxin-channel recognition. Moreover, the simulation result demonstrates that the hydrophobic interactions are important in interaction of negatively charged toxins with potassium channels. The results of our docking/molecular dynamics simulations indicate that our 3D model structure of the kappa-Hefutoxin1-complex is both reasonable and acceptable and could be helpful for smarter drug design and the blocking agents of Kv1 channels.     

The subepithelial gland in ants: a novel exocrine gland closely associated with the cuticle surface

Two glandular systems were discovered that secrete their products onto the cuticular surface in ants. The first, the subepithelial gland, was previously undescribed in ants, and is found throughout the body just beneath the epithelium. This gland consists of independent secretory units, each made up of a single gland cell and an associated duct cell that penetrates the cuticle. Its ultrastructural appearance is consistent with possible hydrocarbon production. Examining 84 ant species, the subepithelial gland was found in eight subfamilies (out of 13), although not necessarily in all species. In a single ant species, Harpegnathos saltator, it was the epithelium itself that was enlarged and functioned as a gland. The enlarged epithelial cells secrete their products directly onto the cuticle through distinct cuticular crevasses.     

REVIEW: Lycaenid-ant interactions of the Maculinea type: tracing their historical roots in a comparative framework

Parasitic relationships between lycaenid butterfly larvae and ants are contrasted with the more common, and ancestral, mutualistic butterfly-ant associations. Three types of lycaenid-ant parasitism can be recognized: (i) the Miletinae type (derived from predation on Homoptera); (ii) the Aphnaeini type (derived from obligate and specific mutualism or commensalism); and (iii) the Maculinea type (derived from facultative mutualism, only represented by the genera Maculinea and Lepidochrysops). Parasitic lycaenid-ant interactions are rare (37 confirmed recorded cases worldwide) and are mostly confined to single species, or small species-groups, in larger non-parasitic clades. Only the two genera representing the Maculinea type have undergone substantial radiation. Ant-parasitic lycaenids predominantly occur in highly seasonal habitats with an extended unfavourable dry or cold season. These observations suggest that (a) parasitic interactions are relatively unstable in evolutionary time, and (b) their evolution usually started with caterpillars seeking shelter in ant nests. Ecological and zoogeographical data for species of the Glaucopsychiti (of which Maculinea forms a part) are compiled and used to discuss the evolutionary origin of ant-parasitism in Maculinea butterflies in a comparative framework. These comparisons suggest that (a) Maculinea evolved from facultative unspecific ant-mutualists, (b) the loss of larval tentacle organs is primarily related to their endophytic feeding habits, (c) that Lamiaceae were the hostplants of ancestral Maculinea, and (d) that Maculinea evolved in eastern central Asia. Further phylogenetic and biogeographical analyses are required to quantitatively test these possibilities. © Rapid Science Ltd. 1998     

Interspecific interactions in a tri-trophic arthropod system: effects of a spider on the survival of larvae of three predatory ladybirds in relation to aphids

The effects of the crab spider, Misumenops tricuspidatus (Fabricius), on the larval survival of three ladybird species, Harmonia axyridis Pallas, Coccinella septempunctata L., and Propylea japonica L., in relation to aphids were investigated in the laboratory. Predation by the spider on the three ladybird species differed. All the larvae of C. septempunctata, none of H. axyridis, and an intermediate number of P. japonica were attacked and eaten by the spider. All the larvae of H. axyridis suffered mortality due to cannibalism or starvation in the treatments with and without a spider. In case of C. septempunctata, however, mortality in the early instars was significantly greater in the treatment with a spider than without a spider and no larvae developed into pupae due to predation. In the treatment without a spider, the majority of the larvae in the former treatment suffered mortality due to cannibalism or starvation, and only 13.3% of larvae developed into the adult stage. In the case of P. japonica, mortality was mainly attributed to predation in the treatment with a spider and only 26.7% became adult. In comparison, 86.7% of larvae survived to the adult stage in the treatment without a spider. In addition, in both H. axyridis and C. septempunctata, the development of young larvae was significantly slower in the presence of a spider, but this was not the case with the older larvae of H. axyridis, which indicates that the effect of the spider on larval development changed with the developmental stage of the larvae in this species. However, the spider had no significant effect on the developmental time of P. japonica larvae. Although both the spider and the ladybirds significantly affected the number of aphids, they did not have an additive effect on aphid abundance. The interactions between the spider and the ladybirds, such as intraguild predation or competition, caused them to reduce aphid population density less than the ladybirds did on their own. The effect of the spider on the larval performance of three predatory ladybirds was found to be unequal in terms of their vulnerability to predation and rate of larval development and it depended on the species and developmental stage of the ladybird.     

Resilience to heat waves in the aquatic snail Lymnaea stagnalis: Additive and interactive effects with micropollutants

相似文献   

Hide, rest or die: a light-mediated diapause response in Daphnia magna to the threat of fish predation

1. In a laboratory batch culture experiment, a diapause response of Daphnia magna to a simulated threat of fish predation was tested at various light intensities, which under natural conditions determine potential vulnerability of Daphnia to visual planktivorous fish. 2. Under moderate light intensity (1.4 μmol m^?2 s^?1) that allows effective predation by fish, the proportion of females producing dormant eggs was significantly higher than under dim light conditions (0.001 μmol m^?2 s^?1) that are not favourable for visual detection of prey. Production of dormant eggs was not observed in complete darkness or in treatments missing fish kairomones, irrespective of tested light conditions. 3. The observed phenomenon is interpreted as a flexible response of prey to the conditional risk of predation assessed by Daphnia according to the presence of fish‐derived cues on the one hand and the presence of dark refugia on the other. Irrespective of the presence of fish kairomones, Daphnia may not produce resting eggs as long as a safe, dark, bottom zone is accessible.     

Tissue sloughing in the sponge Halichondria panicea: a fouling organism prevents being fouled

Summary Specimens of the sponge Halichondria panicea Pallas kept in running sea-water aquaria at 15° C slough off their complete outer tissue layer in regular intervals of three weeks. Sloughing starts at the rim of the oscula and extends over the whole surface within two weeks. Microscopic inspection of the tissue flakes shows them to harbour large numbers of different live organisms, as well as biogenic debris such as pieces of copepod carapaces and diatom frustules. No such community is found on freshly sloughed sponge tissue. After sloughing, the surface skeletal structure of H. panicea is markedly altered, as the characteristic halichondroid reticulum has been replaced by the irregular spicule array typical for the inner sponge tissue. When H. panicea is kept in closed aquaria filled with 0.2 m filtered sea-water, no sloughing occurs during 3 months of maintenance. As those sponges shedding their outer tissue grow steadily at the same time, the tissue sloughing can be regarded as a reaction to sedimentation of organic material and settlement of small organisms on the sponge surface. The sponge thus counteracts clogging of its ostia and prevents the establishment of a micro fouling community on its surface, inhibiting further fouling processes.     

An interfacial equilibria model for the electrokinetic properties of a fat emulsion. Part II: Magnesium,zinc and proton interactions with the interface

Abstract

The semi-empirical thermodynamic model reported in an earlier paper (Hall et al., 1991) is further developed to describe the zeta potential behaviour of an intravenous fat emulsion in the presence of magnesium and zinc cations. The effect of interfacial protonation is also explored. We have now established that a previously reported formation constant for the calcium interaction is actually a conditional value and together with the new data for zinc and magnesium, overall formation constants are calculated.     

Dying from the lesser of three evils: facilitation and non‐consumptive effects emerge in a model with multiple predators

Prey modify their behaviour to avoid predation, but dilemmas arise when predators vary in hunting style. Behaviours that successfully evade one predator sometimes facilitate exposure to another predator, forcing the prey to choose the lesser of two evils. In such cases, we need to quantify behavioural strategies in a mix of predators. We model optimal behaviour of Atlantic cod Gadus morhua larvae in a water column, and find the minimal vulnerability from three common predator groups with different hunting modes; 1) ambush predators that sit‐and‐wait for approaching fish larvae; 2) cruising invertebrates that eat larvae in their path; and 3) fish which are visually hunting predators. We use a state‐dependent model to find optimal behaviours (vertical position and swimming speed over a diel light cycle) under any given exposure to the three distinct modes of predation. We then vary abundance of each predator and quantify direct and indirect effects of predation. The nature and strength of direct and indirect effects varied with predator type and abundance. Larvae escaped about half the mortality from fish by swimming deeper to avoid light, but their activity level and cumulative predation from ambush predators increased. When ambush invertebrates dominated, it was optimal to be less active but in more lit habitats, and predation from fish increased. Against cruising predators, there was no remedy. In all cases, the shift in behaviour allowed growth to remain almost the same, while total predation were cut by one third. In early life stages with high and size‐dependent mortality rates, growth rate can be a poor measure of the importance of behavioural strategies.