A hyperparasite of coccids develops as a primary parasite of fly puparia

Species ofPachyneuron (Hym.: Pteromalidae) have been recorded as either primary parasites or hyperparasites.P. concolor (Foerster) is a polyphagous secondary parasite, attacking encyrtid primary parasites in soft scales, mealy bugs and coccinellid larvae. It also develops as a tertiary parasite. We now report thatP. concolor may also develop as a primary parasite of aphidophagous fly puparia. Host selection in this species appears to be based on locating a soft-bodied host within a hard, dry shell, independent of whether the host is a dipterous pupa in its puparium or a primary parasite in its mummified host. The overall effect ofP. concolor is detrimental. Its introduction into new areas should definitely be avoided.     

Roost selection and roost switching of female Bechstein’s bats (<Emphasis Type="Italic">Myotis bechsteinii</Emphasis>) as a strategy of parasite avoidance

Ectoparasites of vertebrates often spend part of their life cycle in their hosts’ home. Consequently, hosts should take into account the parasite infestation of a site when selecting where to live. In a field study, we investigated whether colonial female Bechstein’s bats (Myotis bechsteinii) adapt their roosting behaviour to the life cycle of the bat fly Basilia nana in order to decrease their contact with infective stages of this parasite. B. nana imagoes live permanently on the bat’s body but deposit puparia in the bat’s roosts. The flies metamorphose independently in the roosts, but after metamorphosis emerge only in the presence of a potential host. In a field experiment, the bats preferred non-contagious to contagious day-roosts and hence were able to detect either the parasite load of roosts or some correlate with infestation, such as bat droppings. In addition, 9 years of observational data on the natural roosting behaviour of female Bechstein’s bats indicate that the bats largely avoid re-occupying roosts when highly contagious puparia are likely to be present as a result of previous occupations of the roosts by the bat colony. Our results indicate that the females adapted their roosting behaviour to the age-dependent contagiousness (emergence probability) of the puparia. However, some infested roosts were re-occupied, which we assume was because these roosts provided advantages to the bats (e.g. a beneficial microclimate) that outweighed the negative effects associated with bat fly infestation. We suggest that roost selection in Bechstein’s bats is the outcome of a trade-off between the costs of parasite infestation and beneficial roost qualities.     

Host status of ‘Scifresh’ apples to the invasive fruit fly species Bactrocera dorsalis,Zeugodacus cucurbitae,and Ceratitis capitata (Diptera: Tephritidae)

We conducted no-choice cage and field infestation studies to determine if the fruit of apples (Malus x domestica L., ‘Scifresh’) are hosts for three invasive tephritid fruit fly species that may enter New Zealand or other apple growing areas. In screen cage tests, punctured and unpunctured (intact) fruit of ‘Scifresh’ apples were exposed to gravid females of Bactrocera dorsalis (Hendel) (Oriental fruit fly), Zeugodacus (Bactrocera) cucurbitae (Coquillet) (melon fly), or Ceratitis capitata (Wiedemann) (Mediterranean fruit fly), outdoors for 24 h and then held on sand in the laboratory for four weeks for pupal development and adult emergence. Unpunctured fruit produced an average of 269.4, 4.3 and 70.1 puparia per kg of fruit for B. dorsalis, Z. cucurbitae and C. capitata, respectively. Punctured fruit produced an average of 619.4, 0.8 and 129.5 puparia per kg of fruit for B. dorsalis, Z. cucurbitae and C. capitata, respectively. By comparison, unpunctured and punctured papaya fruit (Carica papaya, ‘Rainbow’, a preferred host) produced 206–675 and 464–735 puparia per kg of fruit, respectively, across all species. In general, the average weight of individual fruit fly puparia from apple was significantly less (41–71%) than that of puparia reared from papaya, and development times were slower on apple than on papaya. Overall, ‘Scifresh’ apples were a moderately good host for B. dorsalis and C. capitata, and a very poor host for Z. cucurbitae in cage tests. Field exposure of ‘Scifresh’ apples suspended from papaya trees resulted in no infestation by B. dorsalis or Z. cucurbitae under natural conditions. This information will help to inform decisions about quarantine restrictions and potential crop loss in the event of incursions of these fruit flies into apple-producing countries.     

Advances in rearing ofLixophaga diatraeae [Dipt.: Tachinidae]

Larvae ofDiatraea saccharalis (F) were reared on artificial diet in 30-ml cups (1–3 larvae/cup). Adults of the larviparous tachinid parasite,Lixophaga diatraeae (Townsend), were removed from emergence and holding cages with a modified vacuum sweeper. Maggots were extracted from 10 to 14-day-old female flies, that had been disinfected with 1% NaOCl by one of two methods. In method I, fly uteri were removed and placed in a 10-ml vial containing a 0.15% agar-water solution with 3–4 glass beads; rapid vibration of the vial ruptured the uteri and distributed the maggots in the agar solution. In method 2, whole flies were blended with 50-ml water in a blender, and maggots were separated from fly particles by screening; then they were suspended in the agar solution. A procedure was devised for determining the number of maggots obtained by each method. The maggot-agar solution was injected into cups containing host larvae and maggots sought out and parasitized the host larvae; however, the percentage producing puparia generally decreased with increases of host larva and/or maggot density. Puparia were harvested from cups by hand and washed in 1% NaOCl to disinfect and destroy host larval webbing.     

Limited protection of the parasitoid Pachycrepoideus vindemiae from Drosophila suzukii host‐directed spinosad suppression

Laboratory trials were conducted to determine whether the spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), puparium can provide an effective physical barrier to protect immature stages of the pupal parasitoid Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) from spinosad treatments. Spinosad insecticides are currently an important suppression strategy for D. suzukii in organically managed fruit orchards although they are well known to cause mortality in hymenopteran parasitoids. High adult P. vindemiae female mortality (83%) occurred within 24 h of exposure to D. suzukii pupae treated with 10 mg a.i. l^?1 spinosad and female parasitoids did not avoid the pupae treated with similar low levels of spinosad in choice tests that included untreated pupae. Pachycrepoideus vindemiae develops as an idiobiont ectoparasitoid on host fly pupa within the sclerotized host puparium. Significant P. vindemiae survival and emergence was recorded when parasitized D. suzukii puparia were exposed to field treatment levels of spinosad; however, the parasitoid survival was dependent on the time of the spinosad treatment of the host post‐parasitization. Significant parasitoid survival occurred when the host puparia were treated at 2 weeks when the parasitoid was in the pupal stage but did not occur when the host puparia were treated at 1 week post‐parasitization, when the parasitoids were still in a larval stage. The parasitoid adults consumed or otherwise came in contact with residual degrading spinosad when they exited the treated host, and consequently high and low adult parasitoid mortality occurred when the adults emerged from puparia treated at 2 and 1 week(s), respectively. Our study indicates that generally the integration of P. vindemiae parasitism into a sustainable D. suzukii management program is not compatible with spinosad treatments, although P. vindemiae in the pupal stage inside sclerotized host puparia appear to be minimally impacted by spinosad treatments, provided that the spinosad degrades before parasitoid emergence.     

Some effects of low oxygen partial pressures on the development of Calliphora vomitoria;

The influence of wet conditions and low pO₂ on the survival and development of non-feeding final instar larvae and puparia of Calliphora vomitoria has been investigated. The larvae delay the formation of the puparium in wet conditions in air and in dry or wet conditions in 10 and 5% oxygen. This may be related to the susceptibility of the newly formed puparia to oxygen shortage. The pupal respiratory horns play an important part in maintaining O₂ uptake when the puparia are surrounded by particles covered with a film of water but are not involved in aiding survival in low pO₂. Zero age puparia are killed by a 2 day exposure to 10% O₂ but later stages can continue to develop in this gas. Fifty per cent of the 0, 1 and 9 day old puparia are killed by about a 12 hr exposure to 1% O₂ whereas 50 per cent of the 2 to 8 day old puparia can survive over 1·5 days exposure to this gas. Development, as measured by respiration rates and the timing of the emergence of the adults, is delayed by 1% O₂ by the amount of time that the insects spend in that gas. However, the first phase of elongation of the pharate adult longitudinal flight muscle, occurring between the third and fourth day of puparial life, is only slightly slowed down in 1% O₂. The variations in susceptibility to 1% O₂ and the growth of the muscles are discussed in relation to published accounts of protein synthesis in the puparium.     

A circular analysis of chronobiology of Schistosoma japonicum cercarial emergence from hilly areas of Anhui,China

About 46 mammal species have been suspected as reservoir hosts for Schistosoma japonicum and therefore the track of the target parasites, in relation to definitive host species, may be of great importance in terms of theoretical and practical implications. The circadian rhythm of cercariae emergence, a genetically controlled behavior for parasites to adapt to their definitive hosts, may seem to be a perfect biological marker for S. japonicum. In this study, a late (or nocturnal) cercarial emergence pattern was observed on the parasites from one hilly region in Anhui of China, where rodents serve as reservoirs, and on the first generation of the parasites. Moreover, by using the circular statistics, the homogeneity of parasites in such trait was also demonstrated. All these provide evidence for the genetically controlled biological trait, which seems essential in the investigation of macro- or micro-dynamics of parasite transmission of interest. This is particularly true in the case of S. japonicum when multiple parasite isolates or strains are more likely to exist.     

Laboratory Culture and Life History of Heleidomermis magnapapula in Its Host, Culicoides variipennis (Diptera: Ceratopogonidae)

The mermithid parasite Heleidomermis magnapapula was maintained in larvae of the midge Culicoides variipennis for 20 months in enamel pans containing nutrient-rich water and polyester pads as a substrate. Inseminated female mermithids were introduced to the pad surface when the host was in the late second or early third-instar. Host larvae were harvested from the pans 9 days after exposure and held in tap water for nematode emergence. Preparasite yield was positively correlated with female nematode size and averaged 1,267 preparasites/female. Male and female nematodes emerged an average of 12.2 and 13.4 days after host exposure, respectively. Supplemental host food (Panagrellus) during the final days of parasitism did not alter time of emergence. Parasites emerging singly were 64% females, whereas superparasitized hosts yielded males (up to nine/host). Nematode carryover into the adult midge normally occurred at a level of 0.5-2.5%. Parasite load (nematodes/ parasitized individual) in midge adults was lower than that of larvae from the same cohort, and adult midges were more likely to harbor female parasites. Exposure of fourth-instar host larvae resulted in higher levels of adult parasitism (up to 17%).     

Similar yet different: co-analysis of the genetic diversity and structure of an invasive nematode parasite and its invasive mammalian host

Animal parasitic nematodes can cause serious diseases and their emergence in new areas can be an issue of major concern for biodiversity conservation and human health. Their ability to adapt to new environments and hosts is likely to be affected by their degree of genetic diversity, with gene flow between distinct populations counteracting genetic drift and increasing effective population size. The raccoon roundworm (Baylisascaris procyonis), a gastrointestinal parasite of the raccoon (Procyon lotor), has increased its global geographic range after being translocated with its host. The raccoon has been introduced multiple times to Germany, but not all its populations are infected with the parasite. While fewer introduced individuals may have led to reduced diversity in the parasite, admixture between different founder populations may have counteracted genetic drift and bottlenecks. Here, we analyse the population genetic structure of the roundworm and its raccoon host at the intersection of distinct raccoon populations infected with B. procyonis. We found evidence for two parasite clusters resulting from independent introductions. Both clusters exhibited an extremely low genetic diversity, suggesting small founding populations subjected to inbreeding and genetic drift with no, or very limited, genetic influx from population admixture. Comparison of the population genetic structures of both host and parasite suggested that the parasite spread to an uninfected raccoon founder population. On the other hand, an almost perfect match between cluster boundaries also suggested that the population genetic structure of B. procyonis has remained stable since its introduction, mirroring that of its raccoon host.     

Functional response to host density by the egg parasiteTrichogramma pretiosum

The effect of host density on parasitism byTrichogramma pretiosum Riley was studied by exposing groups of 150, 300, 600 or 1200 eggs of potato tuber moth to 2, 4 or 8 female parasites per group. The parasite exhibited a type 2 functional response. As host density increasedT. pretiosum parasitised more hosts, but at a decreasing rate. The attack coefficient (a′) decreased as parasite density increased, whereas the handling time (T _h ) remained almost constant. The search rate (a) decreased with increasing host density.T. pretiosum responded to increasing host density by increasing the number of its encounters with hosts and the number of hosts it parasitised only up to host density of 300 when the parasite density was 2 and up to host density of 600 when the parasite densities were greater and then remained almost constant. The observed incidence of parasitism was higher than that expected on the assumption that the parasites behaved the same at higher host densities as at the lowest. When parasite density was raised from 2 to 8 females per group the percentage of female progeny fell from about 73 to about 48%. A 2-fold increase in the number of female progeny was observed when parasite density was reduced from 8 to 2 and also when the host density was raised from 150 to 1200 eggs.     

The impact of host genetic diversity on virus evolution and emergence

Accumulating evidence indicates that biodiversity has an important impact on parasite evolution and emergence. The vast majority of studies in this area have only considered the diversity of species within an environment as an overall measure of biodiversity, overlooking the role of genetic diversity within a particular host species. Although theoretical models propose that host genetic diversity in part shapes that of the infecting parasite population, and hence modulates the risk of parasite emergence, this effect has seldom been tested empirically. Using Rabies virus (RABV) as a model parasite, we provide evidence that greater host genetic diversity increases both parasite genetic diversity and the likelihood of a host being a donor in RABV cross‐species transmission events. We conclude that host genetic diversity may be an important determinant of parasite evolution and emergence.     

Predictors of Parasitism in Wild White-Faced Capuchins (Cebus capucinus)

Parasite infections in wildlife are influenced by many factors including host demography, behavior and physiology, climate, habitat characteristics, and parasite biology and ecology. White-faced capuchins (Cebus capucinus) host a suite of gastrointestinal and pulmonary parasites, yet the mechanisms affecting host susceptibility and parasite transmissibility have not been examined in this host species. We used the information-theoretic approach (Akaike’s information criterion) and traditional null-hypothesis testing to determine which host characteristics, behaviors, or environmental factors affected the presence of two prevalent capuchin parasites (Filariopsis barretoi and Strongyloides sp.) as well as parasite species richness in four groups of wild capuchins from September 2007 to January 2008 and January to August 2009. Older capuchins were more likely to be infected with Filariopsis barretoi and had higher parasite species richness. Age-biased nematode infections may stem from age differences in capuchin behavior and physiology while high species richness likely results from long- term exposure to numerous parasite species. Infections with Strongyloides sp. were more likely to occur in the dry season when capuchins often descend to the forest floor to drink from terrestrial water sources, potentially increasing their risk of infection from soil-borne larvae. Capuchin behaviors were poor predictors of parasitism, as were female rank, host sex, home range size, and habitat quality. Many of our results were atypical for primate parasitology, suggesting that host–parasite interactions, and subsequently infection risk, may differ in highly seasonal habitats such as tropical dry forests where these monkeys occur.     

Aleochara suffusa andA. bilineata (Col.: Staphylinidae) as parasitoids of brassica root flies in northern Norway

A sample ofDelia puparia collected in late autumn from a brassica field at Tromsø, northern Norway, was investigated to study the level of parasitism byAleochara. BothA. suffusa andA. bilineata were reared from puparia of the cabbage root fly,Delia radicum, and the bean seed flies,D. florilega and/orD. platura. Only two specimens ofA. bilineata emerged from puparia of the turnip root fly,D. floralis. BothAleochara species hibernated in the larval state and both pupated inside the host puparium. Most specimens ofA. suffusa emerged from small hosts (D. florilega/D. platura), whereas the majority of A.bilineata emerged from host species of larger size (D. radicum/D. floralis). The time to develop from first instar larva to adult was similar for bothA. suffusa andA. bilineata. Parasitoids developing in large hosts emerged later than those in small hosts, the delay being the same for both species ofAleochara.     

The energy burden of the bopyrid parasite Argeia pauperata (Crustacea,isopoda) on the grass shrimp Crangon franciscorum (Crustacea,crangonidae)

• 1.1. The relationship between host and parasite rates of energy metabolism was used to estimate the energy burden of Argeia pauperata on its host Crangon franciscorum.
• 2.2. Respiration rates of the host were not significantly affected by the parasite even though the caloric turnover rate of the parasite was more than three times that of the host.
• 3.3. The ratios of both energy expenditure and size of the parasite to those of the host were positively correlated with host size.

     

Nosema pyrausta infection in Macrocentrus grandii, a braconid parasite of the European corn borer, Ostrinia nubilalis

Macrocentrus grandii which develop within Nosema pyrausta-infected larvae of the European corn borer, Ostrinia nubilalis, develop direct systemic infections from the ingestion of spores at the time of larval emergence from the host. Infections adversely affect pupal development and adult longevity. Infected females are unable to transmit the microsporidian to additional corn borer hosts. Pathogen development in the parasite host appears identical to its development in the corn borer host and mature spores show no morphological differences in size or shape when observed at the ultrastructural level. The prevalence of infection in natural parasite populations is 53.8% and closely parallels the 56.7% prevalence of infection in corn borer populations. Results suggest N. pyrausta may play a significant role in limiting M. grandii populations when levels of N. pyrausta in corn borers are high.     

Phylogenetic and environmental DNA insights into emerging aquatic parasites: implications for risk management

Species translocation leads to disease emergence in native species of considerable economic importance. Generalist parasites are more likely to be transported, become established and infect new hosts, thus their risk needs to be evaluated. Freshwater systems are particularly at risk from parasite introductions due to the frequency of fish movements, lack of international legislative controls for non-listed pathogens and inherent difficulties with monitoring disease introductions in wild fish populations. Here we used one of the world’s most invasive freshwater fish, the topmouth gudgeon, Pseudorasbora parva, to demonstrate the risk posed by an emergent generalist parasite, Sphaerothecum destruens. Pseudorasbora parva has spread to 32 countries from its native range in China through the aquaculture trade and has introduced S. destruens to at least five of these. We systematically investigated the spread of S. destruens through Great Britain and its establishment in native fish communities through a combination of phylogenetic studies of the host and parasite and a novel environmental DNA detection assay. Molecular approaches confirmed that S. destruens is present in 50% of the P. parva communities tested and was also detected in resident native fish communities but in the absence of notable histopathological changes. We identified specific P. parva haplotypes associated with S. destruens and evaluated the risk of disease emergence from this cryptic fish parasite. We provide a framework that can be applied to any aquatic pathogen to enhance detection and help mitigate future disease risks in wild fish populations.     

Toxicity of certain insecticides toSturmiopsis inferens,a larval parasite of sugarcane moth borers

Susceptibility of adults and puparia ofSturmiopsis inferens Tns. [Tachinidae, Diptera] to 9 commonly recommended insecticide sprays against sugarcane pests was determined. The chemicals tested as emulsifiable concentrates include lindane 0.1%, endosulfan 0.1%, monocrotophos 0.05%, quinalphos 0.05%, malathion 0.1%, dimethoate 0.1%, cypermethrin 0.01%, fenvalerate 0.01% and decamethrin 0.0014%. Lindane, malathion, dimethoate monocrotophos and quinalphos were highly toxic, while decamethrin had little harmful effect to the adults when exposed for 6 h to filter paper impregnated or sugarcane shoot bits sprayed with the chemicals. However, the insecticides had no harmful effect on the puparia and adult emergence was normal from the puparia sprayed with insecticides. In another study, susceptibility of adults to soil application of lindane EC, carbofuran G, chlorpyriphos G, Sevidol G and whorl application of lindane G, chlorpyriphos G and Sevidol G was tested in pot culture. Except for soil application of lindane EC, all other chemicals had no harmful effect to the adults in pot culture experiment. In a field trial, commonly recommended insecticides against shoot borer,Chilo infuscatellus Snell.viz., soil application of granules of lindane, carbofuran, chlorpyriphos and Sevidol and folia spray of endosulfan did not affect the parasite activity. Institute Publication No 1030.     

Stabilization of mineralized and sclerotized puparial cuticle of muscid flies

Calcium, magnesium and phosphorus are the major mineral elements in puparial exuviae of the face fly, Musca autumnalis, house fly, M. domestica and stable fly, Stomoxys calcitrans, but they are 20–50 times more prevalent in face fly than in the other two species that sclerotize the puparium. Carbon and nitrogen are approx. 5 times more abundant in house fly puparia than in face fly puparia. Face fly puparia contain two and three-fold less total amino acids than the house fly and stable fly, respectively. β-Alanine is a major amino acid in puparial cuticle of the house fly and stable fly, but it is absent in the face fly. There is no significant difference in glucosamine (chitin) content between the three species. Dopamine is the major catechol detected in face fly puparial cuticle while N-β-alanyldopamine (NBAD) is 10 to 15 times more prevalent than other catechols such as dopamine, N-acetyldopamine (NADA), 3,4-dihydroxyphenylalanine (DOPA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in house fly and stable fly puparial cuticles. The latter two species have 75 to nearly 200 times higher levels of extractable catechols than the face fly. At the onset of pupariation, dopamine and NBAD attain nearly equivalent titres in puparial cuticles of face fly and house fly, respectively. Dopamine subsequently decreases more than 40-fold in the face fly as the cuticle becomes stabilized, while NBAD continues to accumulate in the house fly. The house fly covalently incorporates about 150 times more catechols in the puparium than does the face fly. The force required to fracture house fly and stable fly puparia is about three-fold greater than that required to fracture face fly puparia of comparable thickness. However, the face fly puparium attains a strength comparable to those of house fly and stable fly puparia by significantly increasing its thickness. These results demonstrate that dipterans use both catecholamines and minerals for stabilization of puparial cuticle with the house fly and stable fly relying primarily on sclerotization and the face fly on mineralization.     

Endemic infection reduces transmission potential of an epidemic parasite during co-infection

Endemic, low-virulence parasitic infections are common in nature. Such infections may deplete host resources, which in turn could affect the reproduction of other parasites during co-infection. We aimed to determine whether the reproduction, and therefore transmission potential, of an epidemic parasite was limited by energy costs imposed on the host by an endemic infection. Total lipids, triacylglycerols (TAG) and polar lipids were measured in cockroaches (Blattella germanica) that were fed ad libitum, starved or infected with an endemic parasite, Gregarina blattarum. Reproductive output of an epidemic parasite, Steinernema carpocapsae, was then assessed by counting the number of infective stages emerging from these three host groups. We found both starvation and gregarine infection reduced cockroach lipids, mainly through depletion of TAG. Further, both starvation and G. blattarum infection resulted in reduced emergence of nematode transmission stages. This is, to our knowledge, the first study to demonstrate directly that host resource depletion caused by endemic infection could affect epidemic disease transmission. In view of the ubiquity of endemic infections in nature, future studies of epidemic transmission should take greater account of endemic co-infections.