Conifer phloem is typically nitrogen-poor, constraining the development of phloeophagous bark beetles and the growth of their microbial associates. Mountain pine beetle (Dendroctonus ponderosae Hopkins 1902) galleries contain ophiostomatoid fungi that can supplement insect nutrition, yet these fungi are also consumed by abundant mycetophagous mites. Whether such mites function solely as exploitative consumers or also return nitrogen to fungi through a recycling feedback loop remains unclear. We tested whether a common gallery mite, Histiogaster arborsignis Woodring 1963; the most abundant mycetophagous mite in the mountain pine beetle system, recycles nitrogen to a representative beetle-associated fungus, Ophiostoma montium (Rumbold) von Arx 1952. First, we compared fungal biomass responses to two nitrogen sources, homogenized dead mites and potato infusion, using ergosterol concentration as a proxy. Second, we conducted a two-stage 15N tracer assay in which mites fed on 15N-labeled fungal tissue. Mite carcasses and fecal pellets were collected and analyzed for 15N enrichment. In the second stage, a subset of ¹⁵N-labeled dead mites was incorporated into fresh medium. Unlabeled fungal plugs were then placed onto the amended plates to establish secondary cultures. Isotope analyses showed that mites acquired fungal 15N and that secondary cultures incorporated 15N following exposure to mite-derived material. Together, these results indicate evidence of bidirectional nitrogen transfer between mites and fungi under experimental conditions. This interaction represents a localized recycling pathway that may influence nitrogen retention within beetle-fungus-mite communities, although its ecological consequences for beetles remain uncertain.

Parasite exposure without infection can lead to risk-induced trait responses with potential costs to host fitness or non-consumptive effects (NCEs). The various ways in which NCEs can manifest has gained considerable research attention, but the NCEs of parasite exposure on host mating behaviour remain unknown. Using a host-parasite system involving cactophilic flies (Drosophila nigrospiracula) and ectoparasitic mites (Macrocheles subbadius), we investigated the effects of current and prior parasite exposure (sans infection) on host mating behaviour. Current exposure did not influence host mating behaviour. However, female flies previously exposed to mites exhibited increased copulation latency, and were less likely to mate or be courted by males, suggesting that prior exposure makes females less receptive to mating, or that previously exposed females are less attractive to males. On average, previously exposed males invested less time per mating. Our results demonstrate that prior exposure potentially leads to a trade-off between reproduction and parasite defense even after exposure has ended, likely in favour of increased vigilance and parasite avoidance. While other studies have examined the impact of infection on host behaviour, this study represents the first investigation of NCEs on host mating behaviour. Additionally, our findings suggest that the NCEs of parasite exposure without infection could play an important role in parasite-mediated sexual selection.

Parasite exposure can lead to non-consumptive effects (NCEs) in hosts and research in this area has thus far focused primarily on exposure at the developmental stage known to be infected. Using the Drosophila nigrospiracula-Macrocheles subbadius system, we investigated the impact of parasite exposure at two stages undergoing major developmental changes and/or metamorphosis but not known to be infected (i.e., egg and pupae). Drosophila eggs were exposed to parasites indirectly (caged mites) or directly (free-roaming mites) to test the effects of exposure on egg hatching success and larval development. We then investigated whether M. subbadius can utilize the fly pupae as a resource by measuring host emergence success and mite survival when provisioned with a pre-pharate or post-pharate pupa. We found that eggs in direct contact with mites had an 87% decrease in hatching success compared to unexposed eggs. However, indirect exposure had no effect on hatching success. We also found direct exposure to mites resulted in a 43% reduction in emergence among pre-pharate pupae compared to post-pharate pupae. On average, there was a 69% reduction in mite longevity when offered pupae or water compared to a fly host, suggesting mites cannot parasitize pupae. These results highlight the importance of accounting for host ontogeny as non-consumptive effects may be stage-specific; otherwise, we may be mischaracterizing the total impact of parasite exposure. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)Drosophila nigrospiracula ((sic)(sic))(sic)Macrocheles subbadius ((sic))(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)/(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) ((sic)(sic)(sic)). (sic)(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic))(sic)(sic)(sic)((sic)(sic)(sic)(sic)(sic)(sic))(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)/(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic) M. subbadius (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)87%.(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)43%.(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)69%,(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic);(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

Nosema ceranae and Lotmaria passim are two commonly encountered digestive tract parasites of the adult honey bee (Apis mellifera L.). Although these parasites are associated with colony losses, little is known about how they affect individual bee physiology and behaviour at the colony level. Using locally obtained isolates, we investigated the effects of both single and mixed infections of L. passim and N. ceranae on honey bee vitellogenin (Vg) expression and foraging behaviour. At the first instance of foraging, bees inoculated with either parasite had significantly lower Vg expression than uninoculated bees, with bees from the mixed infection treatment having the lowest Vg expression. Bees from the mixed infection treatment also had significantly higher densities of N. ceranae spores and numerically greater densities of L. passim cells per bee compared with bees inoculated with either parasite alone. In addition, bees from the mixed infection treatment had a significantly younger average foraging age compared with uninoculated bees from the same cohort. Although we did not find any effect of treatment on foraging effort, we discovered that bees inoculated with L. passim alone, or together with N. ceranae, had higher returning rates of foragers than control bees or bees inoculated with N. ceranae alone. Our findings indicate that both parasites can alter individual bee physiology, leading to individual changes in behaviour that could alter colony foraging dynamics. These have the potential to result in smaller, less productive colonies, decreased colony survivorship and reduced income for beekeepers. Crown Copyright (c) 2024 Published by Elsevier Ltd on behalf of Australian Society for Parasitology. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The presence of natural enemies can cause organisms to change habitat use, foraging behavior, and/or resource allocation in response to a perceived risk, responses that may come at the cost of other fitness-related traits. Since most species encounter multiple natural enemies in nature, defensive behaviors against one attacker may make the focal organism more vulnerable to attack by a different natural enemy. Anti-predator behaviors can lead to trait-mediated indirect effects, such as an increased risk of parasitism and vice versa. Few empirical studies have examined the response of a single focal species to the risk of attack by multiple species. Our experiments provided the cactiphilic fly Drosophila nigrospiracula with opportunities to prioritize either anti-predator (e.g., reduced activity) or anti-parasite behavior (e.g., increased activity) at the cost of increased infection or predation, respectively. We experimentally show that when flies were exposed to ectoparasitic mites, in the presence of predator (jumping spider) cues, flies incurred increased levels of infection compared to flies without predator cues. The mean infection prevalence increased by 80% and the infection intensity increased by 180%. However, the presence of parasite cues had no analogous effect on predation rates, which suggests that flies prioritized predation risk over parasite defense at the cost of increased infection. We provide empirical evidence that the presence of multiple threats can lead to trait-mediated indirect effects, with important consequences for host-parasite and food web dynamics, and the ecology of fear.

The presence of parasites can elicit host responses even in the absence of infection. These risk-induced trait responses include altered host behaviours, morphology, and/or physiology, which can trade off with other fitness-related traits. Studies of predator-induced non-consumptive effects (NCEs) have demonstrated that exposure at one life stage can lead to NCEs in the next stage, but no studies to date have examined such an effect of parasite exposure. Numerous NCEs have been demonstrated in larval, pupal and adult stages of Drosophila nigrospiracula exposed to ectoparasitic mites (Macrocheles subbadius). Here we experimentally investigated whether parasite-induced NCEs carry over into subsequent developmental stages (i.e. interstadial effects). We tested the prediction that when flies are exposed to mites during the larval and pupal stages, the subsequent adult stage will exhibit decreased body mass, fecundity and longevity. However, we did not detect downstream effects of parasite exposure on adult body mass, fecundity or longevity. The probability of survival and lifetime fecundity were comparable for previously exposed and unexposed groups. We suggest that when parasite exposure is confined to one developmental stage, and the risk of infection is removed in the subsequent stage, the long-term effects of parasite exposure dissipate. The potential to recover from the interim costs of parasite exposure may provide an added benefit to host dispersal.

Vairimorpha (Nosema) ceranae and Lotmaria passim are two commonly encountered digestive tract parasites of the Western honey bee (Apis mellifera L.). Although these parasites are associated with colony losses, little is known regarding how they affect the bee humoral defense response, particularly at the level of the digestive tract where the parasites are found. Using locally-obtained parasite isolates, the effects of both single and mixed V. ceranae and L. passim infections on the bee humoral defense response were evaluated at the digestive tract level by quantifying the expression of three antimicrobial peptides (apidaecin, defensin-1, hymenoptaecin) at five timepoints post-infection. Parasite density was also monitored in digestive tract tissues at these five timepoints to determine if the parasites, particularly L. passim, have distinct host tissue preferences. In general, it was found that bees do not elicit distinct humoral defense responses within the digestive tract in response to infection with either single or mixed V. ceranae and L. passim infections. Increased L. passim density in hindgut tissues compared to midgut tissues at each of the five timepoints suggests a hindgut preference for the parasite. Interestingly, for bees that received mixed infections, both L. passim and V. ceranae densities were elevated in hindgut tissues, suggesting that there could be an interaction occurring between the two parasites.

The cuticle of arthropods provides the first line of defense against predators, pathogens, and parasites. While most studies focus on the role of cuticular defense against microbial pathogens, few have examined whether the cuticle protects against parasites. Here, we investigate the relative importance of cuticular sclerotization and behavioral defenses in Drosophila nigrospiracula against an ectoparasite (Macrocheles subbadius). We first tested whether newly eclosed (NE; i.e., teneral) flies are more susceptible to parasitism than fully sclerotized (FS) flies. In a separate experiment, we severed the wings to test whether the differential susceptibility between NE and FS flies was explained by wing-mediated defenses. We also performed endurance (negative geotaxis) assays to determine whether reduced physical endurance among NE flies contributed to higher vulnerability to parasitism. We found that regardless of whether wings were intact or removed, the prevalence and intensity of infection was significantly higher among NE flies than among FS flies. The negative geotaxis assay also showed that NE flies had lower endurance than FS flies. Moreover, differences in the probability and severity of parasitism between NE and FS flies were magnified when the wings were removed. These results suggest that while cuticular sclerotization serves as the primary first line of defense, wing-mediated behaviors likely allow flies to avoid or minimize mite attacks, and the effectiveness of these behaviors is likely limited by physical endurance. Differences in morphology and behavior between immature adults (not FS) and mature organisms (FS) may drive variation in parasitism risk across developmental stages.

Sleep serves an essential function, and as such sleep deprivation has numerous negative effects on a wide range of organisms, including Drosophila . The link between sleep and cellular/humoral immunity is well studied, but behavioural immunity has been neglected for the most part. Here, we investigate the role of sleep deprivation on Drosophila nigrospiracula susceptibility to parasitism by the ectoparasitic mite, Macrocheles subbadius . We tested the hypothesis that sleep deprivation reduces behavioural resistance against mites, resulting in higher rates of infection among sleep‐deprived (SD) flies compared to non‐sleep‐deprived flies, and that this is mediated by lower endurance (in negative geotaxis assays) among SD flies. We tested the impact of sleep deprivation on two age groups, flies 14 and 21 days post‐eclosion. The prevalence of infection was 15% higher and mite abundance nearly 3x higher in older flies compared to younger flies. Moreover, older sleep‐deprived flies experienced increased susceptibility to infection and lower climbing endurance compared to control flies. 21‐day‐old SD flies were 11% more likely to be infected and accumulated nearly double the number of mites as control flies. As such, we performed endurance assays on 21‐day‐old flies; control flies were 1.7x more likely to initiate climbing and climbed 6x longer in duration than SD flies. Taken together, our results show that increased susceptibility to parasitism among sleep‐deprived flies is mediated by a concomitant decline in endurance. These findings contribute to our understanding of the importance of sleep and consequently the adverse effects of sleep deprivation on animals, particularly with regard to behavioural immunity.

Endosymbiotic bacteria have a wide range of impacts on host physiology, behavior, metabolism, endurance, and mobility. Recent work found some endosymbionts also impact host sleep duration and quality. These effects may increase as flies age and endosymbiont titers increase. We tested the hypothesis that Spiroplasma poulsonni MSRO negatively impacts sleep in Drosophila melanogaster, and this in turn impairs fly endurance. In geotaxis climbing assays (a proxy for endurance), we found that MSRO impacted climbing endurance but in an age-dependent manner. Among younger flies, MSRO+ flies slept significantly less during dark periods (measured by a Drosophila Activity Monitoring System) compared to uninfected flies, but older MSRO+ flies did not show significant differences in amount of sleep compared to uninfected flies in the same cohort. While MSRO status impacted both sleep and endurance of hosts, endosymbiont-mediated sleep deprivation did not directly explain decreases in fly endurance. We discuss these results in the context of endosymbiont comparative biology.

The chemotaxis responses of soil nematodes have been well studied in bacteriophagic nematodes, plant-parasitic nematodes, entomopathogenic nematodes, and to a lesser extent malacopathogenic nematodes. Free-living stages of parasitic nematodes often use chemotaxis to locate hosts. In this study, we compared the chemotaxis profile of 2 slug-associated nematodes with overlapping host ranges. Phasmarhabditis californica is a facultative parasite that has been shown to express strain-dependent variation in chemoattraction profile. We tested 4 slug species to determine the attraction index of a Canadian strain of Ph. californica and a sympatric necromenic nematode, Pristionchus entomophagus. When tested against a control (distilled water), Ph. californica showed a clear (positive) attraction towards the mucus of slugs Ambigolimax valentianus, Arion rufus, and Arion fasciatus, but not Deroceras reticulatum. However, when given a choice between the mucus of D. reticulatum and Ar. fasciatus in a pairwise test, Ph. californica was strongly attracted to the former. Other pairwise comparisons did not reveal a clear preference for either slug species in the following pairs: D. reticulatum-Ar. rufus, Am. valentianus-Ar. rufus, D. reticulatum-Am. valentianus. The chemotaxis assay for Pr. entomophagus showed an attraction toward D. reticulatum and Ar. fasciatus (tested against controls); the attraction index for Am. valentianus was positive, but this was not statistically significant. In contrast, the attraction index for Ar. rufus was negative, suggesting possible repulsion to the mucus of this slug species. Given that Pr. entomophagus and Ph. californica occupy overlapping habitats, utilize similar hosts, and exhibit similar chemotaxis profiles, there is a potential for direct interaction between these 2 nematodes. Like other members of the genus Pristionchus, Pr. entomophagus may be able to prey upon the co-occurring Ph. californica, such antagonistic interactions could have important implications for the coexistence of these 2 species and Ph. californica in particular as a biocontrol agent against pestiferous slugs.

Parasites can indirectly impact hosts through non-consumptive effects (NCEs) via changes in behaviour, morphology, and/or physiology. These responses can be understood in terms of the ecology of fear (ectoparasites) or the ecology of disgust (endoparasites) framework. We tested the hypothesis that NCEs of parasite exposure (e.g., parasite avoidance and defense) trade off with other important behaviours such as feeding and resting. We predicted that when exposed to parasites (without infection), hosts will increase their defensive behaviors at the expense of feeding. We also posited that history of exposure (without infection), or previous infection would impact the expression of these NCEs. The study system involves a cactophilic fruit fly (Drosophila nigrospiracula) and a naturally occurring parasitic mite (Macrocheles subbadius). First, we assessed how prior mite exposure affected fly behaviour in response to current parasite exposure. Mite presence resulted in increased grooming and movement, but exposure history did not affect these behaviours. However, the interaction between previous and current exposure influenced host feeding and resting behaviours. We found that previously exposed flies increased feeding and decreased resting upon a secondary mite exposure. In a second experiment, we tested the role of infection history on current parasite exposure. Compared with naïve flies, previously infected flies were expected to increase defensive behaviours upon secondary exposure. Flies increased defensive and ambulatory behaviour in the presence of mites, and consequently less time was spent resting but feeding was unaffected. None of the behaviours measured were affected by previous infection status. In general, current parasite exposure resulted in NCEs. Moreover, our results showed that previous exposure (without infection) to parasites may have an even stronger effect upon secondary exposure than infection history. Our study highlights the importance of the ecology of fear and the role that exposure and infection history plays in generating NCEs of parasitism.

Most organisms are at risk of being consumed by a predator or getting infected by a parasite at some point in their life. Theoretical constructs such as the landscape of fear (perception of risk) and nonconsumptive effects (NCEs, costly responses sans predation or infection) have been proposed to describe and quantify antipredator and antiparasite responses. How prey/host species identify and respond to these risks determines their survival, reproductive success and, ultimately, fitness. Most studies to date have focused on either predator-prey or parasite-host interactions, yet habitats and ecosystems contain both parasitic and/or predatory species that represent a complex and heterogenous mosaic of risk factors. Here, we experimentally investigated the behavioral responses of a cactophilic fruit fly, Drosophila nigrospiracula, exposed to a range of species that include parasites (ectoparasitic mite), predators (jumping spiders), as well as harmless heterospecifics (nonparasitic mites, ants, and weevils). We demonstrate that D. nigrospiracula can differentiate between threat and non-threat species, increase erratic movements and decrease velocity in the presence of parasites, but decrease erratic movements and time spent grooming in the presence of predators. Of particular importance, flies could distinguish between parasitic female mites and nonparasitic male mites of the same species, and respond accordingly. We also show that the direction of these NCEs differs when exposed to parasitic mites (i.e., risk of infection) versus spiders (i.e., risk of predation). Given the opposing effects of predation versus infection risk on fly behavior, we discuss potential trade-offs between parasite and predator avoidance behaviors. Our findings illustrate the complexity of risk assessment in a landscape of fear and the fine-tuned NCEs that arise in response. Moreover, this study is the first to examine these behavioral NCEs in a terrestrial system.

Phasmarhabditis (syn. Pellioditis) californica is a facultative parasite that has been marketed as a popular biocontrol agent against pestiferous slugs in England, Scotland, and Wales. The necromenic nematode Pristionchus entomophagus has also been recovered from slugs infected with Ph. californica. In this study, we experimentally investigated the outcome of single and mixed applications of Pr. entomophagus and Ph. californica on the slug Deroceras reticulatum (Müller). Host mortality was comparable for single and mixed applications of Ph. californica, with time to death significantly shorter in both treatment groups compared with controls. However, trials with Pr. entomophagus alone did not cause any significant host mortality relative to controls. Compared with the single Ph. californica applications, mixed applications resulted in 67% fewer infective juveniles establishing in the host, and subsequently far fewer infective juveniles were recovered in the next generation. In contrast, the establishment rate and progeny production in Pr. entomophagus were not impacted by the presence of Ph. californica (i.e., mixed applications). Hence, the presence of Pr. entomophagus had a deleterious effect on the establishment success and progeny production of Ph. californica. Our findings reveal an asymmetrical, antagonistic interaction between Ph. californica and Pr. entomophagus and highlight the importance of understanding the ecological relationships between co-occurring species. A decrease in parasite establishment success and progeny production has the potential to directly impact the persistence, sustainability, and efficacy of Ph. californica as a biological control agent.

Predators negatively affect prey outside of direct attack, and these nonconsumptive effects (NCEs) may cause over half the impacts of predators on prey populations. This "ecology of fear" framework has been extended to host-parasite interactions. The NCEs of parasites are thought to be small relative to those of predators. However, recent research shows ectoparasites exert NCEs on multiple life stages of Drosophila. In this study, we apply recent data to a matrix-based model of fly populations experiencing infection/consumption and NCEs from an ectoparasitic mite. We found the NCEs of parasites on larvae, which are not actively parasitized, decreased the size of simulated host populations. By contrast, the NCEs on adult flies increased population size through compensatory egg production. The negative NCEs on larvae outweighed the positive effects on adults to reduce population size. This study suggests that parasitic NCEs can suppress host populations independent of infection.

1. Non-consumptive effects (NCEs) arise in the presence of parasites even when infection does not occur and can include changes to host behaviour, physiology or morphology. Using the Drosophila nigrospiracula-Macrocheles subbadius fly-mite system, we investigated the impact of parasite exposure (sans infection) during the pupal and adult pre-reproductive stages. 2. First, we exposed fly pupae to mites-either indirectly (caged mites) or directly (free-roaming mites) to test the effects of parasite exposure on pupation success. Second, we tested how exposing adult female flies to mites prior to reproduction affects fecundity during the post-exposure reproductive period. 3. We found that direct exposure to mites significantly decreased the rate of successful eclosion (development from pupa to adult) compared with unexposed pupae; however, the duration of pupation was not significantly affected. The indirect exposure did not have a significant effect on either successful eclosion or duration of pupation. We also found that indirectly exposed (caged mites) females had a significant decrease in the number of offspring produced, but only for the first few days post eclosion, suggesting the effect was reversible after mite removal. 4. NCEs arise after mite exposure during the pupal and pre-reproductive life stage of Drosophila, in the form of decreased eclosion success and fecundity. Investigating the NCEs associated with parasite exposure at various life stages of the host is important in understanding the ecology of fear and its total impact on hosts throughout their entire lifespan, with consequences for host ontogeny and population growth.

Some slug species are considered a nuisance in agriculture and horticulture worldwide, causing economic losses to growers. Phasmarhabditis is a genus of bacteria-feeding nematodes that can parasitize slugs and snails and thus potentially serve as a biological control agent. Canada had no record of Phasmarhabditis until a survey conducted in 2019 reported a Canadian strain of Phasmarhabditis californica from a single Arion rufus slug. To build on this discovery, we surveyed three major agricultural sites, ten greenhouses, and nurseries in Alberta from June to September 2021 to collect pest slug species and investigate their associated nematodes, specifically P. californica. Slugs were collected from the field and returned to the laboratory to check for emerging nematodes on White traps. We collected 1331 slugs belonging to nine species, with Deroceras reticulatum being the most common. Only 45 (3.38%) slug samples were positive for nematodes, and the majority were identified to species level: Alloionema appendiculatum, Caenorhabditis briggsae, Caenorhabditis elegans, Panagrolaimus subelongatus, and Mesorhabditis spiculigera. We did not isolate P. californica from any of the slugs collected from these survey sites, which included the original site where P. californica was discovered. However, four D. reticulatum slugs retrieved from a residential garden sample were infected with P. californica. These findings suggest the possibility of a fragmented distribution of P. californica across Alberta. Future research should focus on extensively surveying agriculture and horticulture sites and residential gardens in different provinces across Canada.

Body size generally correlates intraspecifically with insect fitness but can also correlate with parasite abundance (number of parasites). Host preferences by parasites, and variation in host immunity, could contribute to this trend. We investigated the effect of host size on mite-fly interactions (Macrocheles subbadius and Drosophila nigrospiracula). Mites strongly preferred to infect larger flies in pair-wise choices, and larger flies were more likely to be infected and acquired more mites in infection microcosms. Preferences of parasites resulted in size-biased infection outcomes. We discuss the implications of this heterogeneity in infection on parasite overdispersion and fly populations.

The mere presence of predators or parasites can negatively impact the fitness of prey or hosts. Exposure to predators during an organism's development can have deleterious effects on juvenile survival and the subsequent adult stage. Currently, it is unknown if parasites have analogous impacts on host larval stages and whether these effects carry over into other subsequent life stages. However, parasites may be exerting widespread yet underestimated non-consumptive effects (NCEs). We tested if Drosophila nigrospiracula larvae avoid pupating near mite cues (caged Macrocheles subbadius ) in arena experiments, and measured the rate of pupation in arenas with mites and arenas without mites. Larvae disproportionately pupated on the side of arenas that lacked mite cues. Furthermore, fewer larvae successfully pupated in arenas containing mites cues compared to arenas without mite cues. We found that ectoparasitic mites exert NCEs on Drosophila larvae, even though the larval stage is not susceptible to infection. We discuss these results in the context of parasite impacts on host population growth in an infectious world.

Nosema ceranae and Lotmaria passim are two commonly encountered digestive tract parasites of the honey bee that have been associated with colony losses in Canada, the United States, and Europe. Though honey bees can be co-infected with these parasites, we still lack basic information regarding how they impact bee health at the individual and colony level. Using locally-isolated parasite strains, we investigated the effect of single and co-infections of these parasites on individual honey bee survival, and their responsiveness to sucrose. Results showed that a single N. ceranae infection is more virulent than both single L. passim infections and co-infections. Honey bees singly infected with N. ceranae reached < 50% survival eight days earlier than those inoculated with L. passim alone, and four days earlier than those inoculated with both parasites. Honey bees infected with either one, or both, parasites had increased responsiveness to sucrose compared to uninfected bees, which could correspond to higher levels of hunger and increased energetic stress. Together, these findings suggest that N. ceranae and L. passim pose threats to bee health, and that the beekeeping industry should monitor for both parasites in an effort correlate pathogen status with changes in colony-level productivity and survival.