Andrew J. Jajack

Fungicide Contamination Reduces Beneficial Fungi in Bee Bread Based on an Area-Wide Field Study in Honey Bee, Apis mellifera, Colonies

Fermentation by fungi converts stored pollen into bee bread that is fed to honey bee larvae, Apis mellifera, so the diversity of fungi in bee bread may be related to its food value. To explore the relationship between fungicide exposure and bee bread fungi, samples of bee bread collected from bee colonies pollinating orchards from 7 locations over 2 years were analyzed for fungicide residues and fungus composition. There were detectable levels of fungicides from regions that were sprayed before bloom. An organic orchard had the highest quantity and variety of fungicides, likely due to the presence of treated orchards within bees’ flight range. Aspergillus, Penicillium, Rhizopus, and Cladosporium (beneficial fungi) were the primary fungal isolates found, regardless of habitat differences. There was some variation in fungal components amongst colonies, even within the same apiary. The variable components were Absidia, Alternaria, Aureobasidium, Bipolaris, Fusarium, Geotrichum, Mucor, Nigrospora, Paecilomyces, Scopulariopsis, and Trichoderma. The number of fungal isolates was reduced as an effect of fungicide contamination. Aspergillus abundance was particularly affected by increased fungicide levels, as indicated by Simpsons diversity index. Bee bread showing fungicide contamination originated from colonies, many of which showed chalkbrood symptoms.

Pollen feeding in Balaustium murorum (Acari: Erythraeidae): visualization and behaviour

To determine whether pollen is a significant food source for Balaustium cf. murorum (tentative identification), behavioural responses to pollen feeding were examined in short-range Petri plate bioassays. Evans blue dye was used as a tracer to stain pollen after being incorporated into the gut. The results show that all active stages (larva, deutonymph and adult) ingested whole pollen from viburnum shrub (Viburnum) and daffodil (Narcissus) cultivars. All active stages fed on all types of pollen tested: tulip (Tulipa), daffodil (Narcissus), pear (Pyrus), maple (Acer), viburnum (Viburnum) and crabapple (Malus) cultivars except for tulip in the adult and tulip, pear and crabapple in the deutonymph. A higher percentage of larvae fed on pollen-covered surfaces and cleared pollen at a faster rate than other life stages in the bioassays. Clearance of viburnum and daffodil pollen by larvae and deutonymphs was particularly rapid, but this shifted to maple and crabapple pollen in the adult. In pheromone bioassays, pollen-fed larvae, deutonymphs and adults did not prompt clustering or avoidance by free-ranging mites. Our conclusion is that B. murorum can feed on pollen from different sources, no attraction-aggregation pheromone or alarm pheromone is emitted by fed mites and pollen feeding is more important for larvae that emerge in early spring when other food options are scarce.

Off-host aggregation in the non-fed, female brown dog tick, Rhipicephalus sanguineus (Latreille), is induced by tick excreta and enhanced by low relative humidity.

We report that Rhipicephalus sanguineus (Ixodida: Ixodidae) faeces and its main component, guanine, act as assembly pheromones in short‐range Petri plate bioassays. Arrestment activity in response to guanine was lower than that in response to natural excreta, indicating the presence of other active ingredients in natural excreta. The selective removal of appendages was used to establish the important roles played by the palps and the front pair of legs in the detection of the pheromone. Reaction to chemically pure guanine at varying concentrations occurred without a dose response; thus only the presence of guanine, not a critical amount, is required to induce assembly. Higher speed and intensity of clustering occurred at 33% relative humidity (RH). We conclude that female adults of R. sanguineus are more prone to assemble under dry conditions that match the arid microhabitats preferred by this species and that this tendency allows this tick to reside in human dwellings and dog kennels that maintain standards of comfort at 30–50% RH. Cleaning or removing tick excreta‐covered surfaces on which ticks aggregate from within and around human dwellings may prove useful as a means of interfering with the establishment of off‐host clusters of R. sanguineus.

Water balance characteristics of pupae developing in different size maggot masses from six species of forensically important flies

The impact of maggot mass size on body water content, net transpiration rate, and dehydration tolerance of fly pupae was examined in six species of necrophagous flies. Species that spent more time on food as larvae, produced pupae with high body water contents. Dehydration tolerance limits of pupae were modest, matching the moisture-rich conditions of decaying carrion for larvae. Protophormia terraenovae pupariates on food as it dries, and this was reflected by pupae having the highest body water content and lowest net transpiration rate. Megaselia scalaris featured the lowest body water content and highest dehydration tolerance, implying that this species is arid-suited, which matches its ability to feed and colonize on post-decay carrion. Lucilia illustris was the most sensitive to larval overcrowding, resulting in a dramatic decrease in pupal size, early dispersal from food, fed less and had fast net transpiration rates. By contrast, Lucilia sericata was the most resistant, by showing no pupal size decrease and no change in net transpiration rate. Other species were between these extremes, requiring larger maggot mass sizes to produce the effect of decreasing pupal size and increasing net transpiration rate. We conclude: (1) the pupas response to overcrowding and water balance profile are species-specific, varying according to pupal size and net transpiration rate as independent characteristics; (2) water balance profile of the pupae reflects the behavior and microhabitat of the larva; and (3) danger of lethal desiccation to smaller-sized pupae is circumvented by a faster developmental rate rather than enhanced water conservation.

Knot formation reduces water exchange by adult males of the hairworm, Paragordius varius (Nematomorpha: Gordioidea)

To examine how aggregation by hairworms may enhance survival in freshwater, we determined water balance characteristics of Paragordius varius in groups of different sizes. P. varius is hyperosmotic resulting in high body water content and functions down to one-half of water stores. Absence of a critical transition temperature implies a watertight, low-porosity cuticle. Aggregated worms lose water slowly, as a physiological consequence of reduced motor activity. The water balance strategy shifts from a reliance on high dehydration tolerance for isolated individuals, affording high water loss rates, to suppressed activation energy when aggregated, wherein blocking water gain is important when water loss is slower. Low water loss rate derives from stillness and aggregating that facilitate mating or anti-predator defense, rather than as a behavior to regulate water loss. Presence of hairworms in streams is an indicator of high-quality water that is necessary to maintain water balance.

Engorged nymphs act as a conditioning stage to protect adult American dog ticks and lone star ticks (Acari: Ixodidae) against heat stress

To correlate proper development and survival with moulting in hot summers for adults of the American dog tick Dermacentor variabilis and the lone star tick Amblyomma americanum, the maximum heat shock response was determined for engorged nymphs. An impressive ability to moult successfully with near complete adult survival occurred with 1-hour heat shock as high as 46°C for both species. Heat shock exposures at and above 48°C were detrimental, disrupting regular life history pattern by extending the crawling phase and severely reducing the number of adults that emerged. Amblyomma americanum was characterized by completion of adult development from engorged nymphs, greater adult yield, and enhanced adult survival in response to short-term heat exposure up to 50°C for engorged nymphs and 54°C for adult females. Both species featured the improved ability to recover from heat-induced injury as adults following prior exposure to heat at an ecologically relevant temperature (32ºC) as an engorged nymph. Capacity for recovery from heat-related injury was particularly heightened for A. americanum. We conclude that A. americanum is more heat tolerant than D. variabilis, engorged nymphs are a conditioning stage for acclimating adults to high temperature, and negative effects of heat stress on fed nymphs is unlikely to prevent, but may delay, adult development at the temperatures that occur naturally.

Snakes produce kairomones that induce aggregation of unfed larval blacklegged ticks Ixodes scapularis (Acari: Ixodidae)

We have observed in the field copperhead snakes with Ixodes scapularis larvae feeding near the head and cloaca opening. Results show that copperhead excreta acts as a host cue that causes a significant proportion of unfed I. scapularis larvae to stop crawling, curl their legs, and remain motionless in short range bioassays. Clustering of larvae on snake excreta-treated surfaces occurred within one hour and aggregations remained for up to 12 hours. Shed skins of copperheads also prompted arrestment of larval activity (i.e., mobility has stopped). Similar levels of arrestment were noted when testing shed skins and excreta from captive ball pythons (Python regius), Burmese pythons (Python moralus), Mexican cantils (Agkistrodon bilineatus), and variable kingsnakes (Lampropeltis mexicana), suggesting that chemical cues utilized by larvae are similar among snake species. Larvae reacted positively by arresting to uric acid (main purine component in reptile excreta) and squalene (main lipid on shed snake skin). Uric acid and squalene function as tick arrestants, not attractants; physical contact with these compounds is required in order for larvae to settle. Snakes defecate and molt outside dens. The conclusion is that snakes generate two tick kairomones, uric acid and squalene. These compounds promote off-host clustering of unfed I. scapularis larvae in areas likely to be frequented by snakes and their prey such as mice, small lizards, and ground-dwelling birds that serve as tick hosts.

Assembly behaviour by the lone star tick, Amblyomma americanum (Acari: Ixodidae), to tick excreta is not species-specific and influenced by relative humidity

This study tested the lone star tick, Amblyomma americanum, vector of ehrlichiosis, tularemia, Southern tick-associated rash illness borreliosis, for arrestment to excreta from different tick species. The purpose was to explore off-host clustering along with spread and establishment into habitats occupied previously by other ticks. This response was analysed in relation to relative humidity since this is environmental. Females had the greatest responses towards natural excreta, and excreta components guanine and uric, and nymphs behaved like adults but with lower response levels. Response was poor by larvae, by showing inconsistent, or no response to excreta exposure. Clustering occurred on excreta from Amblyomma maculatum, Dermacentor variabilis, Ixodes scapularis, and Rhipicephalus sanguineus. This indicates there is unlikely a species-specific assembly component in excreta of A. americanum. In fact, highest level of assembly by A. americanum was to I. scapularis excreta. Greater speed and intensity for assembly occurred at 33% RH, with more ticks engaged in clustering on excreta-coated surfaces, than at 93% RH. No avoidance reaction was observed when exposed to other tick species excreta, suggesting that excreta from heterospecifics do not repel A. americanum. We conclude that dehydrating conditions cause lone star ticks to more actively pursue optimal moisture-rich, favourable habitats signalled by tick excreta. This behaviour is more important for females and nymphs than larvae, and there is capacity to recognize excreta of overlapping tick species. This co-recognition could facilitate occurrence of A. americanum with other ticks such as I. scapularis that are frequently sympatric with A. americanum through much of their geographic distribution.

The effects of water exposure, soil conditions, and fungus exposure on hatching of the larval lone star tick, Amblyomma americanum (Acari: Ixodidae)

We examined whether water functions as a developmental cue for hatching in the lone star tick, Amblyomma americanum. The experiments examined various exposure routes to water: submersion, relative humidity and an ecologically relevant setup of moist soil along with soil fungi to mimic fungus–egg interactions at oviposition sites. We demonstrate that eggs survive for up to a week underwater; increasing water entry into the egg suppresses hatching; and exposure to liquid water, H2O or D2O, neither shortens nor prolongs the incubation period of those eggs that remain viable. In response to relative humidity, hatching takes place most readily when the air is nearly or fully saturated (with water); relative humidity neither shortens nor extends incubation period; and the length of incubation time is unrelated to the percentage of larvae that hatch. When incubated with fungi (common soil isolates), Aspergillus niger, Metarhizium anisopliae, Penicillium glabrum, Rhizopus stolonifer, Scopulariopsis brevicaulis, eggs tolerate being inundated with fungus mycelium (except for A. niger and the entomopathogen M. anisopliae) and complete development to hatching, albeit in reduced percentages. There was no triggering effect on shortening incubation time and larvae hatching as a result of exposure to these various soil fungi. We conclude that the egg is adapted to multiple types of water stress conditions.

Madagascar hissing cockroach mite, Gromphadorholaelaps schaeferi, prevents fungal infection in its cockroach host: evidence for a mutualistic symbiosis

In this study, we provide the first evidence that the mite Gromphadorholaelaps schaeferi is beneficial to the Madagascar hissing cockroach Gromphadorhina portentosa by participating in a cleaning symbiosis and thus prolonging the life of its host. Gromphadorholaelaps schaeferi is a permanent resident of the cockroach and reduces mould levels by removing the food debris from the cockroach that acts as a substrate for fungal growth. To investigate the mould clearance attributes of these mites, we determined the effectiveness of mite infestation for decreasing cockroach mortality from a topically applied entomopathogenic fungus Metarhizium anisopliae. We further determined the effects of regulating cockroach food levels on altering the mycoflora profile of the cockroaches, with and without mites. Results showed that the lifespan of the cockroaches is extended by approximately 9 months when infested with mites. When treated with M. anisopliae (107 conidia/ml), which is pathogenic to the cockroach but not to the mite, mite infestation increases cockroach longevity by 65% as compared to uninfested cockroaches. Also, the effects of limiting the food offered to the cockroaches synergize with the cleaning symbiosis relationship to further reduce cockroach surface moulds. As a side observation, limiting food input in the cockroach colony not only reduces total cockroach moulds, but also shifts the fungal competition to favour those strains that are less medically significant, that is, away from an otherwise heavy zygomycete load of Rhizopus spp. and Mucor spp. to mitosporic fungi. Maintaining a healthy mite population, and reducing the amount of food kept in the cages, when keeping the hissing cockroach in captivity can potentially reduce fungal load and therefore any associated (human) allergies.