Cues used by the black fly,Simulium annulus,for attraction to the common loon (Gavia immer)

The parasitic relationship between a black fly, Simulium annulus, and the common loon (Gavia immer) has been considered one of the most exclusive relationships between any host species and a black fly species. To test the host specificity of this blood‐feeding insect, we made a series of bird decoy presentations to black flies on loon‐inhabited lakes in northern Wisconsin, U.S.A. To examine the importance of chemical and visual cues for black fly detection of and attraction to hosts, we made decoy presentations with and without chemical cues. Flies attracted to the decoys were collected, identified to species, and quantified. Results showed that S. annulus had a strong preference for common loon visual and chemical cues, although visual cues from Canada geese (Branta canadensis) and mallards (Anas platyrynchos) did attract some flies in significantly smaller numbers.     

Drug transport mechanisms in helminth parasites: passive diffusion of benzimidazole anthelmintics

Anthelmintic molecules must reach their receptors inside target parasites to exert the pharmacological effect. Available data suggest that the main route of entry of antiparasitic drugs into helminth parasites would be through their external surface. However, it is unclear if trans-tegumental/cuticular penetration is the most important way of entry of benzimidazole (BZD) anthelmintics into their target parasites compared to oral ingestion. The relative involvement of active and passive transport mechanisms has not been defined. The goal of the work reported here was to determine the main processes involved in the entry of BZD anthelmintic molecules into the three main classes of helminth parasites. Adult specimens of Moniezia benedeni (cestode), Fasciola hepatica (trematode) and Ascaris suum (nematode) were incubated in Kreb's Ringer Tris buffer (pH 7.4, 37 degrees C) (1g parasite/10 ml incubation medium) for 15, 45, and 90 min, respectively, in the presence of a concentration gradient of either fenbendazole (FBZ), oxfendazole or triclabendazole sulphoxide (TCBZSO) (1-30 mol/ml, n=4). Dead helminth specimens were also incubated with the same drug concentration gradient. Specimens of F. hepatica with the oral route closed off by ligation were incubated with TCBZSO in the presence or absence of bovine serum albumin. After the incubation time elapsed, samples of parasite material were chemically extracted and prepared for high performance liquid chromatography analysis to measure drug/metabolite concentrations. Equivalent drug concentrations were measured within ligated and non-ligated liver flukes, demonstrating that BZD do mainly penetrate by trans-tegumental diffusion. The higher the concentration of BZD molecules in the incubation medium, the greater their concentration recovered within the helminth parasites. High correlation coefficients (>0.98) were obtained between initial drug concentration in the incubation medium and those measured inside the nematode, cestode, and trematode parasites. FBZ concentrations recovered from tissues of dead cestodes/nematodes over time were significantly greater compared to those measured in living parasites. These differences in drug diffusion may be related to the morphological/functional properties of the parasite's external surfaces. The outcome of the work reported here indicates that passive drug transfer through the external helminth surface is the main transport mechanism accounting for BZD accumulation into target parasites.     

Polymorphic growth in larvae of Maculinea butterflies, as an example of biennialism in myrmecophilous insects

The presence of annual and biennial individuals within the same population has been recently demonstrated in the myrmecophilous butterflies Maculinea rebeli and Maculinea alcon, which present a cuckoo strategy inside Myrmica nests, and Maculinea arion which is a predatory species. Here, we present field and laboratory data on polymorphic larval growth in two other predatory species of Maculinea: M. teleius and M. nausithous. Body mass distributions of pre-pupation larvae were bimodal in both species. These results point to the existence of larvae that develop in 1 or 2 years. We also showed that the probability of pupation depended on larval body mass. In the case of M. teleius, the critical body mass at which larvae have a 50% probability of pupation is about 80 mg. We suggest that polymorphism in Maculinea may have evolved as an adaptation to life in ant nests, a habitat which protects them from predators and provides food. However, the quality of this resource is highly variable and unpredictable. According to the bet-hedging hypothesis, if the habitat is unpredictable, females should have an advantage by producing more variable offspring. In the case of Maculinea butterflies, this may involve maintaining larvae that develop in 1 or 2 years.     

Preimaginal development,adult longevity and fecundity ofEncarsia inaron (Hym.: Aphelinidae) parasitizingSiphoninus phillyreae (Hom.: Aleyrodidae) in California

A laboratory study of preimaginal development, adult longevity and fecundity ofEncarsia inaron (Walker) was conducted. Preimaginal developmental times varied with temperature, from 55–60 d at 15±1°C to 14–17 d at 30±1°C. No development took place at 10°C, which was approximately the developmental minimum estimated from regression analysis of developmental rates vs. temperature in the range 15–30°C. Development was slowed and survival was reduced at 32°C. Females lived an average of 18.6 days and laid a average of 159 eggs/female at 25°C. At 25°C, average preimaginal survival was 59.3%, and the sex ratio was 73.5% female. The net reproductive rate (R₀) forE. inaron calculated from these studies was 69.3, while the intrinsic rate of natural increase was 0.1686 individuals per individual per day. Oviposition was concentrated slightly in third instar nymphs of the host.     

How does the suppression of energy supplementation affect herbage intake,performance and parasitism in lactating saddle mares?

Agroecology opens up new perspectives for the design of sustainable farming systems by using the stimulation of natural processes to reduce the inputs needed for production. In horse farming systems, the challenge is to maximize the proportion of forages in the diet, and to develop alternatives to synthetic chemical drugs for controlling gastrointestinal nematodes. Lactating saddle mares, with high nutritional requirements, are commonly supplemented with concentrates at pasture, although the influence of energy supplementation on voluntary intake, performance and immune response against parasites has not yet been quantified. In a 4-month study, 16 lactating mares experimentally infected with cyathostome larvae either received a daily supplement of barley (60% of energy requirements for lactation) or were non-supplemented. The mares were rotationally grazed on permanent pastures over three vegetation cycles. All the mares met their energy requirements and maintained their body condition score higher than 3. In both treatments, they produced foals with a satisfying growth rate (cycle 1: 1293 g/day; cycle 2: 1029 g/day; cycle 3: 559 g/day) and conformation (according to measurements of height at withers and cannon bone width at 11 months). Parasite egg excretion by mares increased in both groups during the grazing season (from 150 to 2011 epg), independently of whether they were supplemented or not. This suggests that energy supplementation did not improve mare ability to regulate parasite burden. Under unlimited herbage conditions, grass dry matter intake by supplemented mares remained stable around 22.6 g DM/kg LW per day (i.e. 13.5 kg DM/al per day), whereas non-supplemented mares increased voluntary intake from 22.6 to 28.0 g DM/kg LW per day (13.5 to 17.2 kg DM/al per day) between mid-June and the end of August. Hence total digestible dry matter intake and net energy intake did not significantly differ between supplemented and non-supplemented mares during the second and third cycles. In conclusion, supplementing lactating mares at pasture should not be systematic because their adaptive capacities enable to increase herbage intake and ensure foal growth. Further research is needed to determine the herbage allowance threshold below which supplementation is required.     

Regional genetic variation in the major sperm protein genes of Onchocerca volvulus and Mansonella ozzardi (Nematoda: Filarioidea)

Onchocerca volvulus and Mansonella ozzardi are two human filarial parasites present in South and Central America. In the Brazilian Amazonia they are found in sympatry, and the lack of clear morphological diagnostic characters in the microfilariae hinders their identification. The major sperm protein (MSP) gene of both species has been sequenced and characterised to determine its potential as a molecular diagnostic character. The length of the MSP gene is different in each species, and this could be used to detect and differentiate them by running the polymerase chain reaction (PCR) product in an agarose gel. Two major gene groups were identified in O. volvulus with a genetic distance of 6% between them. In M. ozzardi only one major group of genes was observed. The high similarity between the protein amino acid sequence of both filarial species confirms that the MSP has been highly conserved through nematode evolution.     

The importance of fish stocking in the dissemination of parasites throughout a group of reservoirs

In view of the known importance of anthropochore movements of fish in disseminating their parasites, it was hypothesized that local movements of fish between neighbouring water bodies for stocking and management purposes would similarly disseminate their parasites, resulting in a high degree of similarity in the parasite communities of fish in water bodies that have been linked by fish transfers. This hypothesis was tested by comparing the helminth parasite communities in brown trout, Salmo trutta Linnaeus and rainbow trout, Oncorhynchus mykiss (Walbaum), in reservoirs in south west England. In one group of six reservoirs there is a recent history of transfers of rainbow trout, and in the second group of four there have been no transfers over the last decade. There was no difference in mean similarity, using Jaccard's Coefficient and a Percentage Similarity Index, between the helminth faunas of trout in the reservoirs linked by transfers and those not so linked, and the distribution of several individual species of helminths was not consistent with their having been disseminated in the course of fish stockings. The hypothesis is thus rejected and it is concluded that anthropochore transfers of trout between reservoirs have been of little or no significance in the dispersal of parasites throughout the reservoirs or in the transfer of helminths from one reservoir to another. The reasons for this unexpected conclusion are discussed in the light of indications that factors unrelated to fish transfers were important determinants of helminth community composition in individual reservoirs.