Bloodmeal analysis in Culicoides midges collected near horses,donkeys and zebras in the Eastern Cape,South Africa

An upsurge in African horse sickness (AHS) in the Eastern Cape, South Africa, from 2006 led to an epidemiological reassessment of the disease there. Light trapping surveys carried out near horses, donkeys and zebras in 2014–2016 collected 39 species of Culicoides midge (Diptera: Ceratopogonidae) that are potential vectors of AHS. To establish if these midges fed on equids, DNA sequences were obtained from the gut contents of 52 female midges (35 freshly blood‐fed, 13 gravid and four parous), representing 11 species collected across 11 sites. Culicoides leucostictus fed on all three equids. Culicoides bolitinos, Culicoides imicola and Culicoides magnus fed on both horses and donkeys. Culicoides onderstepoortensis fed on donkeys, and Culicoides similis and Culicoides pycnostictus fed on zebras. Bloodmeals from cows, pigs, warthogs, impalas and a domestic dog were also identified in various species, but none of the midges tested had fed on birds. These results contribute to knowledge of the vectorial capacity of several species of Culicoides with regard to AHS in the Eastern Cape and point to potential reservoir hosts, of which donkeys, zebras and domestic dogs have previously been found to harbour AHS. Blood‐fed midges were also obtained throughout winter, indicating the potential for endemic AHS in the province.     

Emerging infectious diseases and animal social systems

Emerging infectious diseases threaten a wide diversity of animals, and important questions remain concerning disease emergence in socially structured populations. We developed a spatially explicit simulation model to investigate whether—and under what conditions—disease-related mortality can impact rates of pathogen spread in populations of polygynous groups. Specifically, we investigated whether pathogen-mediated dispersal (PMD) can occur when females disperse after the resident male dies from disease, thus carrying infections to new groups. We also examined the effects of incubation period and virulence, host mortality and rates of background dispersal, and we used the model to investigate the spread of the virus responsible for Ebola hemorrhagic fever, which currently is devastating African ape populations. Output was analyzed using regression trees, which enable exploration of hierarchical and non-linear relationships. Analyses revealed that the incidence of disease in single-male (polygynous) groups was significantly greater for those groups containing an average of more than six females, while the total number of infected hosts in the population was most sensitive to the number of females per group. Thus, as expected, PMD occurs in polygynous groups and its effects increase as harem size (the number of females) increases. Simulation output further indicated that population-level effects of Ebola are likely to differ among multi-male–multi-female chimpanzees and polygynous gorillas, with larger overall numbers of chimpanzees infected, but more gorilla groups becoming infected due to increased dispersal when the resident male dies. Collectively, our results highlight the importance of social system on the spread of disease in wild mammals.     

Allometric growth and adaptive value of exaggerated body parts in the larvae of Gratiana spadicea (Klug) (Coleoptera: Chrysomelidae)

1. Larvae of tortoise beetles present exaggerated body parts in association with an abdominal shield, which is made of faeces and exuviae that are deposited on the urogomphi throughout ontogeny. Growth trajectories and scaling relationships of these functional structures associated with the shield, if any, are unknown. 2. This study of Gratiana spadicea first tested, under field conditions, whether there is adaptive value associated with the shield regarding protection against predation and sunlight. Then, under laboratory conditions, the growth trajectory and allometric relationships among body parts were investigated, including scoli, individual and apparent furcae, and shield. The influence of food deprivation on the development of these structures was also determined. 3. Findings from previous studies were confirmed, suggesting that the adaptive value assigned to the shield is related to protection against predators. The present study demonstrated for the first time that the shield acts as a parasol in cassidines, decreasing the exposure of their larval body to sunlight. The scoli and apparent furca are exaggerated structures of G. spadicea, the development of which involves allometric growth and greater energetic investment (positive allometry) during ontogeny. There was proportionally less energetic investment for somatic construction of individual furca (negative allometry) due to the accumulation of the exuviae. 4. The possible consequences, in terms of developmental costs and survivorship benefits associated with the evolution of such exaggerated structures, are discussed.     

Narratives of success among Irish and African Caribbean migrants

This paper compares the narratives of two men in midlife who migrated to the UK from Ireland and from the Caribbean as children, in the middle of the last century. We examine how success is narrated over the life course to show how migrants’ positioning of themselves differs from the ways in which they are positioned by outsiders, including in policy and public discourse. We conclude that while outsider narratives often polarise success and failure, insider understandings of success are dynamic and culturally and historically situated.     

Induced defenses of loblolly pine, Pinus taeda: potential impact on Dendroctonus frontalis within-tree mortality

Loblolly pine (Pinus taeda L.) produces an induced defensive hypersensitive response in inner bark colonized by the southern pine beetle, Dendroctonus frontalis Zimm. (Coleoptera: Scolytidae), and its associated fungi. Adult beetles forced to colonize the induced response tissue in a laboratory study constructed galleries that were the same length as adults boring in normal phloem. However, each female laid fewer eggs in the induced tissue. Larval and pupal mortality were also higher in this tissue when compared to surrounding phloem. Beetles colonizing trees in response to pheromone baits constructed less gallery and laid fewer eggs in induced tissue than in surrounding normal phloem. These results suggest that the lesions produced by the induced defense system in conifers may not only contain the growth of fungi inoculated into trees during the attack phase of beetle colonization, but may also affect survival of bark beetle progeny.

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Résumé Une réaction hypersensible de défense a été induite dans les couches profondes de l'écorce de P. taeda colonisée par D. frontalis et le champignon qui lui est associé. Au laboratoire, des adultes, contraints de coloniser les tissus où une réaction hypersensible e été induite, ont foré des galeries de même longueur que celles creusées dans du phloème sain. Cependant les femelles ont pondu moins d'oeufs dans les tissus induits; les mortalités larvaires et nymphales étaient aussi plus fortes dans ce tissu que dans le phloème voisin. Les scolytes, ayant colonisé les arbres après attraction par des pièges à phéromones, forent moins de galeries et pondent moins d'oeufs dans le tissu induit que dans le phloème sain voisin. Ces résultats suggèrent que les lésions, provoquées par le système de défense induit des conifères, peuvent non seulement limiter la croissance du champignon inoculé dans l'arbre au cours de la colonisation des scolytes, mais aussi affecter la survie des descendants dans l'écorce.

     

The age-sex structure of the slave population in Harris County, Texas: 1850 and 1860

The effect of the slave system on demography can be revealed by examining the age-sex structure of slave populations. The age-sex structure of slaves in Harris County, Texas is investigated using the 1850 and 1860 slave schedules. Median ages for black and mulatto slaves suggest that the population was young. Population pyramids exhibit a narrow base and top with a broad middle. The high proportion of slaves between 10 and 30 years of age and the increase in population size between 1850 and 1860 were mainly related to the importation of slaves and only partly due to natural increase. The data also show that black slaves were older on small plantations while mulattoes were older on larger farms. It is suggested that differential treatment in terms of purchase practices, assignment of tasks, food allocation, and/or differential susceptibility to infectious diseases may account for this pattern.     

Life cycle changes during 12 successive generations of laboratory colonisation of the leafroller Cnephasia jactatana (Walker) (Lepidoptera: Tortricidae) on artificial diet

Abstract

Close monitoring of the lepidopteran leafroller Cnephasia jactatana under laboratory colonisation revealed few distinct effects of successive rearing on artificial diet on the life cycle. The second laboratory generation had a prolonged development time and altered sex synchronism in pupation and eclosion patterns. Some deleterious changes were observed in later generations, including decreases in fertility, egg hatch and sperm motility, failure of mating adults to separate, and pupal and adult malformations. These changes were not adaptive, but were due to incompatibility with the general purpose diet (GPD) used; they were absent under sub-colonisation on a sheepnut-bean based diet (SBD). Success in the laboratory colonisation of C. jactatana is attributed to a random mating protocol, choice of environmental conditions representing the wild habitat, and a rapid rate of population growth.