Influence of intertree distance on foraging behaviour of Rhagoletis pomonella in the field

Abstract. 1. We tested a prediction from contemporary foraging theory that animals should decrease their allocation of energy to the searching of individual patches when interpatch travel costs decrease.
2. We used individual Rhagoletis pomonella Walsh (Diptera: Tephritidae) females foraging for oviposition sites (= Crataegus fruit) in a host tree which was surrounded by four other trees at varying distances.
3. We found that flies generally invested less search, measured as time spent searching a tree or number of leaves visited on a tree, when neighbouring trees were nearby than when farther away.
4. Under our test conditions, flies appeared to have difficulty locating neighbouring trees at a distance of more than 1.6 m.
5. Our study calls into question the interpretation of search effort by insects within resource patches in the absence of information on interpatch distances.     

Haematobia irritans parasitism of F1 yak × beef cattle (Bos grunniens × Bos taurus) hybrids

The horn fly Haematobia irritans (Diptera: Muscidae) is a blood obligate ectoparasite of bovids that causes annual losses to the U.S. beef cattle industry of over US$1.75 billion. Climate warming, the anthropogenic dispersion of bovids and the cross‐breeding of beef cattle with other bovid species may facilitate novel horn fly–host interactions. In particular, hybridizing yaks [Bos grunniens (Artiodactyla: Bovidae)] with beef cows (Bos taurus) for heterosis and carcass improvements may increase the exposure of yak × beef hybrids to horn flies. The present paper reports on the collection of digital images of commingled beef heifers (n = 12) and F1 yak × beef hybrid bovids (heifers, n = 7; steers, n = 5) near Laramie, Wyoming (～ 2200 m a.s.l.) in 2018. The total numbers of horn flies on beef heifers and F1 yak × beef heifers [mean ± standard error (SE): 88 ± 13 and 70 ± 17, respectively] did not differ significantly; however, F1 yak × beef steers had greater total horn fly abundance (mean ± SE: 159 ± 39) than female bovids. The present report of this experiment is the first such report in the literature and suggests that F1 yak × beef bovids are as susceptible as cattle to horn fly parasitism. Therefore, similar monitoring and treatment practices should be adopted by veterinarians, entomologists and producers.     

Food sharing: a model of manipulation by harassment

Most analyses of food-sharing behavior invoke complex explanationssuch as indirect and delayed benefits for sharing via kin selectionand reciprocal altruism. However, food sharing can be a moregeneral phenomenon accounted for by more parsimonious, mutualisticexplanations. We propose a game theoretical model of a generalsharing situation in which food owners share because it is in their own self-interest—they avoid high costs associatedwith beggar harassment. When beggars harass, owners may benefitfrom sharing part of the food if their consumption rate islow relative to the rate of cost accrual. Our model predictsthat harassment can be a profitable strategy for beggars if they reap some direct benefits from harassing other than sharedfood (such as picking up scraps). Therefore, beggars may manipulatethe owner's fitness payoffs in such a way as to make sharingmutualistic.     

UDP-Gal: <Emphasis Type="Italic">N</Emphasis>-acetylglucosamine β 1–4 galactosyltransferase expressing live attenuated parasites as vaccine for visceral leishmaniasis

As compared to cutaneous leishmaniasis, vaccination against visceral leishmaniasis (VL) has received limited attention. In this study, we demonstrate for the first time that an UDP-Galactose: N-acetylglucosamine β 1–4 galactosyltransferase (GenBank Accession No. EF159943) expressing attenuated LD clonal population (A-LD) is able to confer protection against the experimental challenge with the virulent LD AG83 parasite. A-LD was also effective in established leishmania infection. The vaccinated animals showed both cell mediated (in vitro T-cell proliferation, and DTH response) and humoral responses (Th1 type). These results demonstrate the potential of the attenuated clones as an immunotherapeutic and immunoprophylactic agent against visceral leishmaniasis.     

Minireview: Metabolic control of the reproductive physiology: Insights from genetic mouse models

This article is part of a Special Issue Energy Balance.     

Spiggin levels are reduced in male sticklebacks infected with Schistocephalus solidus

Using an enzyme-linked immunosorbent assay (ELISA) based technique, Schistocephalus solidus infection was shown to considerably reduce levels of spiggin in the kidney of male three-spined sticklebacks Gasterosteus aculeatus from an oligotrophic upland lake. These results suggested a graduated effect of the infection on the reproductive physiology of male three-spined sticklebacks.     

Cluster analysis as a method for evaluation of genetic similarity in specific host — parasite interaction (Lactuca sativa — Bremia lactucae)

Summary In gene-for-gene systems, specificity of hostparasite interactions is most often estimated qualitatively using the symbols +, –, (i.e. susceptibility and/or resistance). In large sets (interaction patterns) it becomes impossible to analyze numerous data by mere comparison. This is overcome by application of cluster analysis. In our experiments the methods in question were used to estimate the data obtained in a study on interactions between more than 220 Lactuca sativa cultivars and 12 Bremia lactucae physiological races (isolates) of Czechoslovak origin. The matrix of similarity coefficients was analyzed by hierarchical clustering. Similarity and/or dissimilarity of host R-genotypes was graphically expressed using the method of two principal components. The results obtained are related to genetic constitution of race specific resistance of the host and the possibility of predicting effective resistance sources.     

The effects of gregarine parasites on longevity, weight loss, fecundity and developmental time in the field crickets Gryllus veletis and G.pennsylvanicus

ABSTRACT. 1. Gregarines, debilitating gut parasites, significantly reduced longevity and increased weight loss in the field cricket Gryllus pennsylvanicus Burmeiser when adults were kept on suboptimal diets, but in G.pennsylvanicus and G.veletis (Alexander and Bigelow) fed ad libitum , weight change, longevity, and fecundity were not significantly different in infected and control individuals.
2. Adults harbouring gregarines at eclosion took significantly longer to develop from the second and third instars than did uninfected adults.
3. Longevity of nymphs kept in the laboratory without food was decreased in infected individuals compared with uninfected ones, but not significantly so.
4. The evolutionary and ecological implications of nonlethal parasites are discussed.