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Insect outbreaks can cause large scale defoliation of forest trees or destruction of crops, leading to ecosystem degradation and economic losses. Some outbreaks occur simultaneously across large geographic scales and some outbreaks occur periodically every few years across space. Parasitoids are a natural enemy of these defoliators and could help mitigate these pest outbreaks. A holistic understanding of the host-parasitoid interactions in a spatial context would thus enhance our ability to understand, predict and prevent these outbreaks. We use a discrete time deterministic model of the host parasitoid system with populations migrating between 2 patches to elucidate features of spatial host outbreaks. We show that whenever populations persist indefinitely, host outbreaks in both patches can occur alternatively (out of phase) at low migration between patches whereas host outbreaks always occur simultaneously (in phase) in both patches at high migration between patches. We show that our results are robust across a large range of parameters across different modelling approaches used typically to model intraspecific competition among hosts and parasitism, in the host-parasitoid literature. We give an analytical expression for the period of oscillations when the migration is low i.e., when host outbreaks in both patches are out of phase, show it is in agreement with numerical results. We end our paper by showing that we get the same results whether we include the biologically rooted formulations from May et al. (1981) or a general cellular automata model with qualitative rules., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Insects are frequently infected with heritable bacterial endosymbionts. Some of them confer resistance to parasitoids. Such defensive symbionts are sensitive to variation in temperature. Drawing predominantly from the literature on aphids and flies, we show that temperature can affect the reliability of maternal transmission and the strength of protection provided by defensive symbionts. Costs of infection with defensive symbionts can also be temperature-dependent and may even turn into benefits under extreme temperatures, for example, when defensive symbionts increase heat tolerance. Alone or in combination, these mechanisms can drive temperature-associated (latitudinal) clines of infection prevalence with defensive symbionts. This has important consequences for host-parasitoid coevolution, as the relative importance of host-encoded vs. symbiont-provided defenses will shift along such clines., Competing Interests: Declaration of Competing Interest We declare no conflicts of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

This review focuses on biological control interactions in arid areas and is motivated by the need to devise sustainable agricultural practices for a warming and drying world. Parasitoids, important natural enemies of crop pests, are diverse and abundant in natural arid habitats. Dryland croplands, which are usually irrigated, are also rich in local parasitoids. Nevertheless, biological control projects in arid croplands mostly involve imported parasitoids (classical biological control) rather than the conservation of native species. Dryland parasitoids experience heat, drought, low relative humidity, sparse vegetation, and low host densities. Heat resistance combines local genetic adaptations, behavioral and physiological flexibility, and microbial symbioses, but how parasitoids cope with other aridity-related challenges is insufficiently understood. How dryland conditions impact host-parasitoid population dynamics also requires further study., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Ongoing climate change is increasing the frequency and magnitude of high-temperature events (HTEs), causing heat stress in parasitoids and their hosts. We argue that HTEs and heat stress should be viewed in terms of the intersecting life cycles of host and parasitoid. Recent studies illustrate how the biological consequences of a given HTE may vary dramatically depending on its timing within these lifecycles. The temperature sensitivity of host manipulation by parasitoids, and by viral endosymbionts of many parasitoids, can contribute to differing responses of hosts and parasitoids to HTEs. In some cases, these effects can result in reduced parasitoid success and increased host herbivory and may disrupt the ecological interactions between hosts and parasitoids. Because most studies to date involve endoparasitoids of aphid or lepidopteran hosts in agricultural systems, our understanding of heat responses of host-parasitoid interactions in natural systems is quite limited., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Anthropogenic climate change, including temperature extremes, is having a major impact on insect physiology, phenology, behavior, populations, and communities. Hyperparasitoids (insects whose offspring develop in, or on, the body of a primary parasitoid host) are expected to be especially impacted by such effects due to their typical life history traits (e.g. low fecundity and slow development), small populations (being high on the food chain), and cascading effects mediated via lower trophic levels. We review evidence for direct and indirect temperature and climate-related effects mediated via plants, herbivores, and the primary parasitoid host species on hyperparasitoid populations, focusing on higher temperatures. We discuss how hyperparasitoid responses may feed back to the community and affect biological control programs. We conclude that despite their great importance, very little is known about the potential effects of climate change on hyperparasitoids and make a plea for additional studies exploring such responses., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

In nature, most parasitoids attack more than one host species, and nearly all hosts are attacked by several species of parasitoids. This opens many potential opportunities for interactions of invasive species with native parasitoid-host association networks in invaded communities. Despite this, few studies have examined the direct and indirect impacts of biological invasion on parasitoid-host associations. This review examines what is known of these relationships from the most recent literature and suggests future research priorities. We conclude that parasitoid-host association networks in invaded communities are complex, dynamic, and subject to trophic intrusions from invasive plants, herbivores, plant pathogens, parasitoids, and hyperparasitoids. Future studies should take a holistic systems approach to understanding the impact of biological invasion and its consequences in shaping community structure through altering existing native, coevolved parasitoid-host association networks., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. No artifical intellegence assistance was used in writting, reviewing, and editing the manuscript., (Published by Elsevier Inc.)

Parasite proliferations within/on the host form the basis of the outcome of all infectious diseases. However, within-host dynamics are difficult to study in vertebrates, as it requires regularly following pathogen proliferation from the start of the infection and at the organismal level. Invertebrate models allow for this monitoring under controlled conditions using population approaches. These approaches offer the possibility to describe many parameters of the within-host dynamics, such as rate of proliferation, probability to control the infection, and average time at which the pathogen is controlled. New parameters such as the Pathogen Load Upon Death and the Set-Point Pathogen Load have emerged to characterize within-host dynamics and better understand disease outcome. While contextualizing the potential of studying within-host dynamics in insects to build fundamental knowledge, we review what we know about within-host dynamics using insect models, and what it can offer to our knowledge of infectious diseases., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Taeniosis/cysticercosis and echinococcosis are neglected zoonotic helminth infections with high disease burden caused by tapeworms which circulate between definitive and intermediate host reflecting a predator-prey interaction. Taeniid eggs can remain vital for months, allowing arthropods to mechanically transport them to intermediate hosts. However, the multiple routes that arthropods provide as carriers of taeniid eggs are still often unregarded or not considered. This review focuses on the prevalence and importance of arthropods as carriers and spreaders of taeniid eggs in the epidemiology of taeniosis/cysticercosis and echinococcosis. Current scientific knowledge showed a relevant role of houseflies (Muscidae), blowflies (Calliphoridae), dung beetles (Scarabaeoidea), darkling beetles (Tenebrionidae), ground beetles (Carabidae) and skin beetles (Dermestidae) in the spread of taeniid eggs in the environment, which may favor the infection of new hosts through the direct ingestion of an insect or of contaminated food and water. At last, key research challenges are highlighted, illustrating that further knowledge on the topic is needed to develop and improve guidelines and actions to prevent taeniid infections worldwide., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Insect parasitoids have evolved symbiotic interactions with several viruses and thousands of parasitoid species have established mutualistic associations with polydnaviruses (PDVs). While PDVs have often been described as virulence factors allowing development of immature parasitoids inside their herbivore hosts, there is increasing awareness that PDVs can affect plant-insect interactions. We review recent literature showing that PDVs alter not only host physiology, but also feeding patterns and composition of herbivore's oral secretions. In turn PDV-induced changes in herbivore phenotype affect plant responses to herbivory with consequences ranging from differential expression of plant defense-related genes to wider ecological effects across multiple trophic levels. In this opinion paper we also highlight important missing gaps to fully understand the role of PDVs and other parasitoid-associated viral symbionts in a plant-insect interaction perspective. Because PDVs negatively impact performance and survival of herbivore pests, we conclude arguing that PDV genomes offer potential opportunities for biological control., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Insect phenology is affected by climate change and main responses are driven by phenotypic plasticity and evolutionary changes. Any modification in seasonal activity in one species can have consequences on interacting species, within and among trophic levels. In this overview, we focus on synchronisation mismatches that can occur between tightly interacting species such as hosts and parasitoids or preys and predators. Asynchronies happen because species from different trophic levels can have different response rates to climate change. We show that insect species alter their seasonal activities by modifying their life-cycle through change in voltinism or by altering their development rate. We expect strong bottom-up effects for phenology adjustments rather than top-down effects within food-webs. Extremely complex outcomes arise from such trophic mismatches, which make consequences at the community or ecosystem levels tricky to predict in a climate change context. We explore a set of potential consequences on population dynamics, conservation of species interactions, with a particular focus on the provision of ecosystem services by predators and parasitoids, such as biological pest control., (Copyright © 2019. Published by Elsevier Inc.)

Some parasitoids modify the behavior of their hosts, benefiting themselves at the host's expense. This phenomenon is called 'manipulation', and current research on parasitoid manipulation of host behavior tends to fall into one of three categories. First, the frequency of manipulation and the magnitude of its benefits to the parasitoid remains unclear. Basic documentation of manipulations is thus a major research focus, with especially valuable recent data coming from spiders manipulated by Polysphincta wasps. Second, for a handful of systems, we now have sufficient phylogenetic and behavioral data to begin asking questions about how manipulation evolved. Finally, the field continues to probe the mechanisms through which parasitoids manipulate host behavior, and now examines the role of parasitoid symbionts in this interaction., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Virus-insect interactions are primarily parasitic, yet diverse mutualistic interactions, some of which are symbiogenic, also occur. These viruses can modify insect physiology and behavior so that hosts can gain resistance against various biotic challenges like pathogen and parasites. In the recent past, many insect mutualistic viruses have been reported. Viruses can show symbiogenic interactions with some insects, which have been explored at the molecular level. However, understanding about molecular mechanisms for many of the mutualistic viruses is still enigmatic. Exploration of these interactions and its mechanism can shed light on phenomenon of virus mediated biotic stress resistance in insects., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Insect populations are declining even in protected areas, but the underlying causes are unclear. Here, I consider whether the factors driving the loss of insect diversity include invasive and/or introduced insects transmitting pathogens to less-resistant native species. The introduction of insects into new areas for biocontrol, to promote pollination, or for mass rearing in insect farms, threatens the health and diversity of indigenous insects by the co-introduction of entomopathogens whose spillover is difficult to control. Even less virulent pathogens or covert infections can become lethal if environmental stressors weaken the resistance of indigenous host species in an additive, potentiating or synergistic manner. More research is needed to develop effective strategies that protect the health and diversity of native insects., (Copyright © 2019 The Author. Published by Elsevier Inc. All rights reserved.)

Studies have demonstrated that medication behaviors by insects are much more common than previously thought. Bees, ants, flies, and butterflies can use a wide range of toxic and nutritional compounds to medicate themselves or their genetic kin. Medication occurs either in response to active infection (therapy) or high infection risk (prophylaxis), and can be used to increase resistance or tolerance to infection. While much progress has been made over the last few years, there are also key areas that require in-depth investigation. These include quantifying the costs of medication, especially at the colony level of social insects, and formulating theoretical models that can predict the role of infection risk in driving micro-evolutionary and macro-evolutionary patterns of animal medication behaviors., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Some parasites manipulate host behavior by exploiting the host's behavioral control networks. This review explores two examples of this approach using parasites from opposite ends of the size spectrum, that is, viruses and parasitic insects. The first example explores the use of the gene (egt) by some baculoviruses to deactivate the hormone 20-hydroxyecdysone. Suppressing this chemical signal prevents the expression of behaviors that could reduce viral transmission. The second example explores how a parasitic wasp uses the host's immune/neural communication system to control host behavior. When a host's manipulated behavior requires complex neural coordination, exploitation of host behavioral control systems is likely to be involved. Simpler host behaviors can be induced by damage to host tissues., (Copyright © 2019 Elsevier Inc. All rights reserved.)

In insects, bacterial endosymbionts are known to influence the ecology of their hosts by modifying interactions with natural enemies such as parasitoids. Symbionts can modulate both parasitoid behavioral and/or physiological traits as well as host behaviors and life-history traits. Together these suggest that endosymbionts may impact the host range of parasitoids. For example, endosymbionts may narrow parasitoid host range through first, reducing parasitoid ability to locate hosts and/or larval survival, second, affecting fitness traits of the emerging adult parasitoid and/or third, modulating the outcome of interference and exploitative competition between parasitoid species. From both a fundamental and applied point of view, these symbiotic effects would influence the ecology and evolution of parasitoids and associated population-level processes and ecosystem services (e.g. biocontrol)., (Copyright © 2018. Published by Elsevier Inc.)

Endogenous Viral Elements (EVEs) are remnants of viral genomes that are permanently integrated into the genome of another organism. Parasitoid wasps have independently acquired nudivirus-derived EVEs in three lineages. Each parasitoid produces virions or virus-like particles (VLPs) that are injected into hosts during parasitism to function in subversion of host defenses. Comparing the inventory of nudivirus-like genes in different lineages of parasitoids can provide insights into the importance of each encoded function in virus or VLP production and parasitism success. Comparisons revealed the following conserved features: first, retention of genes encoding a viral RNA polymerase and infectivity factors; second, loss of the ancestral DNA polymerase gene; and third, signatures of viral ancestry in patterns of gene retention., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Divergence and escalation in defences promote chemical diversity in plants, and consequently the diversity of insect herbivores. This diversification cascades to insect parasitoids through direct effects on host herbivore susceptibility, changes in herbivore community composition, or disparity in plant volatiles. Large tropical plant genera represent an ideal model for studying these trends due to the high diversity of sympatric species and their insects. Novel measures of chemical structural similarity should be used to analyse evolutionary trends in both direct and indirect defences. Host chemical data need to be combined with detailed herbivore and parasitoid data. This will help to identify truly active compounds. Furthermore, resolved genomic phylogenies for plants and insects should be included to assign directionality in the processes., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Retortamonas spp. has been reported as an intestinal parasite among various host organisms, including humans; however, its intra-genus molecular diversity has not yet been elucidated. Haplotypes of the 18S small subunit ribosomal RNA locus (1836-1899 bp) of Retortamonas spp. from humans (n = 8), pigs (n = 6), dogs (n = 1), goats (n = 16), water buffalos (n = 23), cattle (n = 7), rats (n = 3), and chickens (n = 5) were analyzed with references isolated from non-human mammals, amphibians, and insects. Phylogenetic and network analyses revealed a statistically supported three cluster formation among the vertebrate-isolated haplotypes, while insect-isolated haplotypes were independently clustered with Chilomastix. In the clade of vertebrate isolates, assemblage A (amphibian genotype), which included the amphibian references, was addressed as an out-group of the other clusters. Assemblage B (mammalian and chicken genotype) included most haplotypes from various mammals including humans with the haplotypes isolated from a chicken. Human isolates were all classified into this assemblage, thus assemblage B might correspond to R. intestinalis. Assemblage C (bovine genotype), which included specific haplotypes from water buffalos and cattle, was addressed as a sister lineage of assemblage B. Among the diversified haplotypes of assemblage B, a specific haplotype, which was identified from multiple host mammals (humans, dogs, pigs, cattle, water buffalos, elks, goats, and rats), indicates the potential zoonotic transmission of the Retortamonas among them. The genotyping classification of retortamonads could contribute to a better understanding of its molecular epidemiology, especially among humans and related host organisms., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Insects typically forage in complex habitats in which their resources are surrounded by non-resources. For herbivores, pollinators, parasitoids, and higher level predators research has focused on how specific trophic levels filter and integrate information from cues in their habitat to locate resources. However, these insights frequently build specific theory per trophic level and seldom across trophic levels. Here, we synthesize advances in understanding of insect foraging behavior in complex habitats by comparing trophic levels in specialist host-parasitoid-hyperparasitoid systems. We argue that resources may become less apparent to foraging insects when they are member of higher trophic levels and hypothesize that higher trophic level organisms require a larger number of steps in their foraging decisions. We identify important knowledge gaps of information integration strategies by insects that belong to higher trophic levels., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

Entomopathogenic nematodes in the genus Steinernema (Nematoda: Steinernematidae) have a mutualistic relationship with Xenorhabdus bacteria (Gram-negative Enterobacteriaceae). This partnership however, is pathogenic to a wide range of insect species. Because of their potent insecticidal ability, they have successfully been implemented in biological control and integrated pest management programs worldwide. Steinernema-Xenorhabdus-insect partnerships are extremely diverse and represent a model system in ecology and evolution to investigate symbioses between invertebrates and microbes. The reproductive fitness of the nematode-bacterium partnership is tightly associated, and maintenance of their virulence is critical to the conversion of the insect host as a suitable environment where this partnership can be perpetuated., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Defensive endosymbionts are now understood to be widespread among insects, targeting many different threats, including predators, parasites and disease. The effects on natural enemies can be significant, resulting in dramatic changes in the outcome of interactions between insects and their attackers. Evidence is now emerging from laboratory and field work that defensive symbionts can have important effects on the surrounding insect community, as well as on vulnerable enemy species; for example, by reducing prey available for the trophic level above the enemy. However, there is a need for more experimental work across a greater taxonomic range of species in order to understand the different ways in which defensive symbionts influence insect communities., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Insects commonly possess heritable microbial symbionts that increase their resistance to particular parasites. A diverse community of defensive symbionts may thus provide hosts with effective and specific protection against multiple parasites, although costs might constrain the accumulation of many symbionts. In parallel to the allelic diversity in the MHC complex of the vertebrate immune system, parasite diversity could be the driving force behind symbiont diversity. There is indeed evidence that parasites have the ability to drive frequencies of defensive symbionts in their hosts, and that these symbionts influence parasite communities, but direct evidence that parasite diversity can promote symbiont diversity is still lacking. We provide suggestions to investigate this potential link., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Parasitoids (parasitic wasps) are ubiquitous components of nearly all communities containing plant-insect herbivore associations. Plant toxin defenses against herbivores may also affect higher trophic levels by directly (e.g., plant toxins encountered in host hemolymph) or indirectly (e.g., plant toxins reduce host size/quality or alter the host's immunity against parasitoids). Yet, whether parasitoids structure plant-herbivore interactions remains relatively understudied. Nevertheless, recent meta-analyses and empirical work emphasize the importance of parasitoids in structuring interactions among lower trophic levels. Two promising areas of research are particularly ripe for future exploration: a) the potential for microbes to alter the interactions among plants, insect herbivores, and parasitoids, and b) the effects of climate change on phenological (mis)matches among trophic levels., (Copyright © 2019. Published by Elsevier Inc.)

Immunology textbooks teach us about the ways hosts can recognize and kill microbes but leave out something important: the mechanisms used to survive infections. Survival depends on more than simply detecting and eliminating microbes; it requires that we prevent and repair the damage caused by pathogens and the immune response. Recent work in insects is helping to build our understanding of this aspect of pathology, called disease tolerance. Here we discuss papers that explore disease tolerance using theoretical, population genetics, and mechanistic approaches., (Copyright © 2018. Published by Elsevier Inc.)

Lipid uptake and metabolism by trypanosomatid parasites from vertebrate host blood have been well established in the literature. However, there is a lack of knowledge regarding the same aspects concerning the parasites that cross the hemolymph of their invertebrate hosts. We have investigated the lipid composition and metabolism of the insect trypanosomatid Herpetomonas muscarum by 3 H- palmitic acid and phosphate ( 32 Pi) and the parasite interaction with Lipophorin (Lp) the main lipid carrying protein of insect hemolymph. Gas chromatography-mass spectrometry (GC-MS) analyses were used to identify the fatty acids and sterols composition of H.muscarum. Furthermore, we investigated the Lp binding site in the plasma membrane of parasite by Immunolocalization. We showed that H. muscarum incorporated 3H-palmitic acid and inorganic phosphate (32Pi) which were readily used as precursor molecules of lipid biosynthetic pathways. Furthermore, H. muscarum was able to take up both protein and lipid moieties of Lp which could be used as nutrient sources. Moreover, we have also demonstrated for the first time the presence of a Lp binding site in the membrane of a parasite. Such results point out the role of describing the metabolic pathways of trypanosomatids in order to provide a better understanding of parasite-host interaction peculiarities. Such studies may enhance the potential form the identification of novel chemotherapeutic targets in harmful parasites., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Animals often alter their food choices following a pathogen infection in order to increase immune function and combat the infection. Whether social animals that collect food for their brood or nestmates adjust their nutrient intake to the infection states of their social partners is virtually unexplored. Here we develop an individual-based model of nutritional geometry to examine the impact of collective nutrient balancing on pathogen spread in a social insect colony. The model simulates a hypothetical social insect colony infected by a horizontally transmitted parasite. Simulation experiments suggest that collective nutrition, by which foragers adjust their nutrient intake to simultaneously address their own nutritional needs as well as those of their infected nestmates, is an efficient social immunity mechanism to limit contamination when immune responses are short. Impaired foraging in infected workers can favour colony resilience when pathogen transmission rate is low (by reducing contacts with the few infected foragers) or trigger colony collapse when transmission rate is fast (by depleting the entire pool of foragers). Our theoretical examination of dietary collective medication in social insects suggests a new possible mechanism by which colonies can defend themselves against pathogens and provides a conceptual framework for experimental investigations of the nutritional immunology of social animals., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

All insects, including pest species, are colonized by microorganisms, variously located in the gut and within insect tissues. Manipulation of these microbial partners can reduce the pest status of insects, either by modifying insect traits (e.g. altering the host range or tolerance of abiotic conditions, reducing insect competence to vector disease agents) or by reducing fitness. Strategies utilizing heterologous microorganisms (i.e. derived from different insect species) and genetically-modified microbial symbionts are under development, particularly in relation to insect vectors of human disease agents. There is also the potential to target microorganisms absolutely required by the insect, resulting in insect mortality or suppression of insect growth or fecundity. This latter approach is particularly valuable for insect pests that depend on nutrients from symbiotic microorganisms to supplement their nutritionally-inadequate diet, e.g. insects feeding through the life cycle on vertebrate blood (cimicid bugs, anopluran lice, tsetse flies), plant sap (whiteflies, aphids, psyllids, planthoppers, leafhoppers/sharpshooters) and sound wood (various xylophagous beetles and some termites). Further research will facilitate implementation of these novel insect pest control strategies, particularly to ensure specificity of control agents to the pest insect without dissemination of bio-active compounds, novel microorganisms or their genes into the wider environment., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

When infection alters host behaviour such that the pathogen benefits, the behaviour is termed a manipulation. There are several examples of this fascinating phenomenon in many different systems. Vector-borne diseases are no exception. In some instances, as the term implies, pathogens directly interfere with host processes to control behaviour. However, host response to infection and host physiology are likely to play important roles in these phenotypes. We highlight the importance of considering host response and physiology from recent work on altered host-seeking in malaria parasite-infected mosquitoes and argue that this general approach will provide useful insights across vector-borne disease systems., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Blastocystis is a common unicellular eukaryotic parasite found not only in humans, but also in various kinds of animal species worldwide. Since Blastocystis isolates are morphologically indistinguishable, many molecular biological approaches have been applied to classify these isolates. The complete or partial sequences of the small subunit rRNA gene (SSU rDNA) are mainly used for comparisons and phylogenetic analyses among Blastocystis isolates. However, various lengths of the partial SSU rDNA sequence have been used for phylogenetic inference among genetically different isolates. Based on the complete SSU rDNA sequences, consensus terminology of nine subtypes (STs) of Blastocystis sp. that were supported by phylogenetically monophyletic nine clades was proposed in 2007. Thereafter, eight additional kinds of STs comprising non-human mammalian Blastocystis isolates have been reported based on the phylogeny of SSU rDNA sequences, while STs 11 and 12 were only proposed on the base of partial sequences. Although many sequence data from mammalian and avian Blastocystis are registered in GenBank, only limited data on SSU rDNA are available for poikilotherm-derived Blastocystis isolates. Therefore, the phylogenetic positions of the reptilian/amphibian Blastocystis clades are unstable. The phylogenetic inference of various STs comprising mammalian and/or avian Blastocystis isolates was verified herein based on comparisons between partial and complete SSU rDNA sequences, and the phylogenetic positions of reptilian and amphibian Blastocystis isolates were also investigated using 14 new Blastocystis isolates from reptiles with all known isolates from other reptilians, amphibians, and insects registered in GenBank., (Copyright © 2016. Published by Elsevier Ireland Ltd.)

In occupying an intermediate trophic position, herbivorous insects serve a vital link between plants at the base of the food chain and parasitoids at the top. Although these herbivore-mediated indirect plant-parasitoid interactions are well-documented, new studies have uncovered previously undescribed mechanisms that are fundamentally changing how we view tri-trophic relationships. In this review we highlight recent advances in this field focusing on both plant-driven and parasitoid-driven outcomes that flow up and down the trophic web, respectively. From the bottom-up, plant metabolites can impact parasitoid success by altering host immune function; however, few have considered the potential effects of other plant defense strategies such as tolerance on parasitoid ecology and behavior. From the top-down, parasitoids have long been considered plant bodyguards, but in reality the consequences of parasitism for herbivory rates and induction of plant defensive chemistry are far more complicated with cascading effects on community-level interactions., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The parasitic life cycle of Leishmania includes an extracellular promastigote stage that occurs in the gut of the insect vector. During that period, the sucrose metabolism and more specifically the first glycosidase of this pathway are essential for growth and survival of the parasite. We investigated the expression of the invertase BfrA in the promastigote and amastigote stages of three parasite species representative of the three various clinical forms and of various geographical areas, namely Leishmania major, L. donovani and L. braziliensis. Thereafter, we cloned, overexpressed and biochemically characterized this invertase BfrA from L. major, heterologously expressed in both Escherichia coli and L. tarentolae. For all species, expression levels of BfrA mRNA were correlated to the time of the culture and the parasitic stage (promastigotes > amastigotes). BfrA exhibited no activity when expressed as a glycoprotein in L. tarentolae but proved to be an invertase when not glycosylated, yet owing low sequence homology with other invertases from the same family. Our data suggest that BfrA is an original invertase that is located inside the parasite. It is expressed in both parasitic stages, though to a higher extent in promastigotes. This work provides new insight into the parasite sucrose metabolism., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Entomopathogenic nematodes are effective biological control agents against insect pests but their commercial application is restricted by their limited shelf life. This study applies our knowledge of the cold tolerance of nematodes to this problem and investigates further the cold tolerance mechanisms of Steinernema feltiae and Heterorhabditis bacteriophora infective juveniles. When frozen using a fast freezing regime these nematodes are moderately freezing tolerant, with a lower lethal temperature of -5°C. Survival is significantly enhanced by slow freezing overnight (at -1°C), with a decrease in the lower lethal temperature to -14°C. This may indicate that these nematodes are capable of cryoprotective dehydration. Acclimation at 5°C further enhanced freezing survival in S. feltiae but only by a small amount. Nematodes that had survived freezing to -13°C retained their pathogenicity to an insect host. Rapid cold hardening or exposure to a cold shock had no significant effect on freezing survival. The further development of methods based on cryoprotective dehydration may result in a method for the commercial storage of these nematodes., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Nutrition is critical to immune defence and parasite resistance, which not only affects individual organisms, but also has profound ecological and evolutionary consequences. Nutrition and immunity are complex traits that interact via multiple direct and indirect pathways, including the direct effects of nutrition on host immunity but also indirect effects mediated by the host's microbiota and pathogen populations. The challenge remains, however, to capture the complexity of the network of interactions that defines nutritional immunology. The aim of this paper is to discuss the recent findings in nutritional research in the context of immunological studies. By taking examples from the entomological literature, we argue that insects provide a powerful tool for examining the network of interactions between nutrition and immunity due to their tractability, short lifespan and ethical considerations. We describe the relationships between dietary composition, immunity, disease and microbiota in insects, and highlight the importance of adopting an integrative and multi-dimensional approach to nutritional immunology., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)

Intraguild predation (IGP) is a widespread ecological phenomenon in which two consumers that share a resource also engage in a predator-prey interaction. Theory on IGP predicts the occurrence of alternative stable states, but empirical evidence of such states is scarce. This raises the question of whether alternative states are a rare phenomenon that is unlikely to be observed in nature. Here we analyze a model in which the resource exhibits logistic or chemostat dynamics and consumers have saturating (Type II) functional responses. We show that alternative states can arise for a wide range of biological scenarios and that environmental constraints can make their detection difficult. Our analysis identifies three possible combinations of alternative states: (i) IG prey or IG predator, (ii) coexistence or IG predator, and (iii) coexistence or IG prey. Bifurcation diagrams reveal that alternative states are possible over large regions of the parameter space. However, they can be limited to narrow ranges along the resource productivity axis, which may make it difficult to observe the occurrence of alternative states in communities with IGP. Microcosm experiments provide a promising avenue for detecting combinations of asymptotically stable states along a productivity gradient.

Delayed host self-regulation using a Beverton-Holt function and delayed logistic self-regulation are included in a host-pathogen model with free-living infective stages (Anderson and May's model G) with the purpose of investigating whether adding the relatively complex self-regulations decrease the likelihood of population cycles. The main results indicate that adding delayed self-regulation to the baseline model increases the likelihood of population cycles. The dynamics display some of the key features seen in the field, such as cycle peak density exceeding the carrying capacity and a locally stable equilibrium coexisting with a stable cycle (bistability). Numerical studies show that the model with more complex forms of self-regulation can generate cycles which match most aspects of the cycles observed in nature.

The ability of organisms to adapt to fluctuating food conditions is essential for their survival and reproduction. Accumulating energy reserves, such as lipids, in anticipation of harsh conditions, will reduce negative effects of a low food supply. For Hymenoptera and Diptera, several parasitoid species lack adult lipogenesis, and are unable to store excess energy in the form of lipid reserves. The aim of this review is to provide a synthesis of current knowledge regarding the inability to accumulate lipids in parasitoids, leading to new insights and prospects for further research. We will emphasize physiological mechanisms underlying lack of lipogenesis, the evolution of this adaptation in parasitoids and its biological implications with regard to life history traits. We suggest the occurrence of lack of lipogenesis in parasitoids to be dependent on the extent of host exploitation through metabolic manipulation. Currently available data shows lack of lipogenesis to have evolved independently at least twice, in parasitic Hymenoptera and Diptera. The underlying genetic mechanism, however, remains to be solved. Furthermore, due to the inability to replenish adult fat reserves, parasitoids are severely constrained in resource allocation strategies, in particular the trade-off between survival and reproduction.

Recent evolutionary studies have suggested that females have a more robust immune system than males. Using two damselfly species (Hetaerina americana and Argia tezpi), we tested if females produced higher immune responses (as phenoloxidase and hydrolytic enzymes), had a higher survival (using a nylon implant inserted in the abdomen and measuring survival after 24h) and fewer parasites (gregarines and water mites) than males. We also tested whether immune differences should emerge in different body areas (thorax vs. abdomen) within each sex with the prediction that only females will differ with the abdomen having a higher immune response than their thorax since the former area, for ecological and physiological reasons, may be a target zone for increased immune investment. Animals were adults of approximately the same age. In both species, females were more immunocompetent than males, but only in H. americana females were immune responses greater in the abdomen than in the thorax. However, there were no differences in survival and parasite intensity or the probability of being parasitised between the sexes in either of the two species. Thus, this study lends partial support to the principle that females are better at defending than males despite the null difference in parasitism and survival.

In this paper we develop a novel discrete, individual-based mathematical model of the evolution of life history, dispersal and other behavioural characteristics in insect host-parasitoid-microbe associations, and use it to investigate their evolutionary dynamics. For any individual characteristic the model begins with an even, rectangular distribution of characteristic values. Selection is then allowed to act, and the change in the distribution of the characteristic values is observed. Evolutionary change in the population variance of the characteristic value is also observed, since we would expect this to decline under selection in most cases. The paper, therefore, introduces a general framework for modeling problems of evolution in stochastic, spatially structured environments, where movement and dispersal are under selection. The model then extends this approach to include the sex-distorting bacterium Wolbachia in order to investigate aspects of its horizontal and vertical transmission under different levels of superparasitism by parasitoids. The model also includes a neutral genetic marker, in order to be able to detect changes in phenotype frequency caused by genetic drift, as well as a simplified simulation of sexual reproduction so as to allow the possibility of recombination between genotypes. Key results from the model simulations show that: (i) the refractory time after oviposition affects the value of superparasitism, with short refractory times favouring high rates of superparasitism; (ii) variable levels of superparasitism do not affect the stable proportion of the population of parasitoids infected with Wolbachia, but this is achieved by different evolutionary pathways under low and high superparasitism, respectively. In the case of low superparasitism Wolbachia spreads mainly by vertical transmission, leading to population replacement, whereas when superparasitism rates are high there is significant horizontal transfer.

Within many agricultural systems, insect pests and their natural enemies are forced to persist as a metapopulation, continuously recolonizing patches following disturbance through harvesting or spraying with insecticides. Despite the need to understand factors influencing biocontrol success, few theoretical studies of host-parasitoid interactions have examined the potential impact of local disturbance within a metapopulation framework. Here, we add periodic local mortality to series of classical host-parasitoid models to examine its effect on host suppression and parasitoid persistence. Using a deterministic lattice model, we show that despite the wide range of complex dynamics generated at the patch level, the region wide pattern of disturbance is the key factor influencing host suppression. The level of host suppression achieved can be understood in terms of both the strength of density dependent parasitism, and the relative amounts of host and parasitoid mixing amongst patches of different ages. Local dispersal among patches is sufficient to ensure coexistence of the host and parasitoid, though persistence is not necessarily associated with the formation of self-organized spatial structures reported in previous studies. Finally, a stochastic version of the model is developed, in order to highlight how the effects of demographic stochasticity may influence biocontrol success in highly disturbed agricultural systems.

We describe the intermediate and definitive hosts of the fish nematodes Rhabdochona coronacauda and R. denudata honshuensis and discuss the relationships between parasitism and the feeding habitats of their intermediate hosts. We found that the principal intermediate hosts of the two nematodes were filter-feeding mayflies of the genera Ephemera, Photamanthus and Isonychia. Ephemera strigata seemed to be the most important intermediate host of these nematodes. Adult R. coronacauda were found mainly in Hemibarbus longirostris and Rhinogobius flumineus, which are benthic fishes that feed on benthic aquatic insects, including E. strigata. For R. coronacauda, therefore, the feeding habits of the definitive hosts facilitate host alternation by this species. However, adult R. denudata honshuensis were found in cyprinids. In particular, Zacco temmincki was the principal natural definitive host in our study area. Since Z. temmincki is a swimming predator, E. strigata nymphs that burrow in the substrate are not the main prey of this species. This indicates that the transmission of R. denudata honshuensis hardly occurs from E. strigata nymph to Z. temmincki, suggesting another, unknown transmission route.

When several competitors deplete a patch, it can be advantageous for each of them to stay provided that others leave, whereas, on the other hand, staying longer decreases the expected payoff for everyone. This situation can be considered as a generalized war of attrition. Previous studies have shown that optimal patch leaving strategies become stochastic and the expected leaving time is much larger than predicted by the marginal value theorem when competitors interfere. The possibility of superparasitism, as occurs for example in parasitoids, induces such interference. In addition, it gives several complications. First, the payoff of females that have left the patch is affected by the ovipositions of the remaining individuals. Second, differences in the arrival time of females cause payoff-relevant asymmetries, since females that arrived early on have parasitized more hosts in a patch at the moment superparasitism starts than those that arrived later. We show that this can be modelled as an asymmetric generalized war of attrition, and derive global characteristics of the ESS for simultaneous decisions on when to start superparasitism and when to leave a patch.

Females of many animal species mate with several different males, despite the extra costs. Recent studies in social insects now suggest that the resulting increase in genotypic variance in offspring is beneficial under selection by parasites. This finding also helps to understand the evolution and maintenance of sexual reproduction.

The insect stage of the protozoan parasite Leishmania mexicana secretes a filamentous acid phosphatase (secreted acid phosphatase, SAP), a polymeric phosphoglycoprotein. The wild-type (wt) SAP filament is a copolymer composed of two related gene products SAP1 and SAP2, which are identical in the enzymatically active NH2-terminal domain and the COOH-terminal domain, but differ in the length of a highly glycosylated Ser/Thr-rich repeat region (32 amino acids and 383 amino acids, respectively) which is located between these domains. When expressed separately, full length SAP1, SAP2, or the NH2-terminal domain alone, are able to assemble into filaments. The Ser/Thr-rich region is the exclusive target for a novel type of O-glycosylation via phosphoserines. By using glycerol spraying/low-angle rotary metal shadowing and labelling with monoclonal antibodies it is demonstrated that the repetitive region adopts an extended conformation forming side arms which project radially from the filament core and terminate with the COOH-terminal domain. The length of the side arms of SAP1 and SAP2 (20 nm and 90 nm, respectively) corresponds to the predicted length of the Ser/Thr-rich repeat region of SAP1 and SAP2. Mass determination by scanning electron microscopy (STEM) shows that one morphologically defined globular particle of the filament core is a polypeptide dimer. We propose a model for the filament core, in which the globular NH2-terminal SAP domains form one strand composed of polypeptide dimers or two tightly associated strands of monomers which may twist into a double helix, similar to actin filaments. The highly O-glycosylated side arms project from the filament core conferring an overall bottle-brush-like appearance. The L. mexicana SAP is compared to SAPs secreted by the closely related species L. amazonensis and L. donovani., (Copyright 1998 Academic Press.)

Mouse macrophages were infected with bloodstream, tissue culture-derived and axenic culture-derived trypomastigotes of the Y and the CL strains of Trypanosoma cruzi. The percentage of infected cells, the mean number of parasites per cell and the incorporation index were determined after 2 h of interaction. Longer periods of interaction were used to evaluate the fate of the different trypomastigotes inside the macrophage. It was observed that the incorporation of T. cruzi by the macrophages was high for tissue culture-derived trypomastigotes, intermediate for axenic culture-derived trypomastigotes and low for bloodstream trypomastigotes. For the three types of trypomastigotes, a larger number of macrophages were infected with parasites from the Y than the CL strain. These results suggest that the ability to infect macrophages is a basic characteristic of each strain which is maintained when the parasites are transferred from the vertebrate of the invertebrate host to in vitro systems.