Biomedical subjects

K Tracy Reynolds

Publications and source records attributed to K Tracy Reynolds.

3 recordsLinked to original sources

PubMed2004

Superparasitism: a non-adaptive strategy?

Although once thought to be detrimental, superparasitism (where a host is parasitized more than once) by solitary parasitoids is now accepted to be an adaptive strategy. However, a recent study reveals that this might not always be the case. Varaldi et al. show that the superparasitism behaviour of the wasp Leptopilina boulardi is caused by a vertically and horizontally transmitted infectious agent. A reinterpretation of the adaptive significance of superparasitism in this species might therefore be required.

Journal Article↗

PubMed2003

The effects of host age, host nuclear background and temperature on phenotypic effects of the virulent Wolbachia strain popcorn in Drosophila melanogaster.

Because of their obligate endosymbiotic nature, Wolbachia strains by necessity are defined by their phenotypic effects upon their host. Nevertheless, studies on the influence of host background and environmental conditions upon the manifestation of Wolbachia effects are relatively uncommon. Here we examine the behavior of the overreplicating Wolbachia strain popcorn in four different Drosophila melanogaster backgrounds at two temperatures. Unlike other strains of Wolbachia in Drosophila, popcorn has a major fitness impact upon its hosts. The rapid proliferation of popcorn causes cells to rupture, resulting in the premature death of adult hosts. Apart from this effect, we found that popcorn delayed development time, and host background influenced both this trait and the rate of mortality associated with infection. Temperature influenced the impact of popcorn upon host mortality, with no reduction in life span occurring in flies reared at 19 degrees. No effect upon fecundity was found. Contrary to earlier reports, popcorn induced high levels of incompatibility when young males were used in tests, and CI levels declined rapidly with male age. The population dynamics of popcorn-type infections will therefore depend on environmental temperature, host background, and the age structure of the population.

Age Factors↗

PubMed2002

Male age, host effects and the weak expression or non-expression of cytoplasmic incompatibility in Drosophila strains infected by maternally transmitted Wolbachia.

In Drosophila melanogaster, the maternally inherited endocellular microbe Wolbachia causes cytoplasmic incompatibility (CI) in crosses between infected males and uninfected females. CI results in a reduction in the number of eggs that hatch. The level of CI expression in this species has been reported as varying from partial (a few eggs fail to hatch) to nonexistent (all eggs hatch). We show that male age in this host species has a large impact on the level of CI exhibited and explains much of this variability. Strong CI is apparent when young males are used in crosses. CI declines rapidly with male age, particularly when males are repeatedly mated. Wolbachia from a Canton S line that was previously reported as not causing CI does in fact induce CI when young males are used in crosses, albeit at a weaker level than in other D. melanogaster strains. The strain differences in CI expression are due to host background effects rather than differences in Wolbachia strains. These results highlight the importance of undertaking crosses with a range of male ages and nuclear backgrounds before ascribing particular host phenotypes to Wolbachia strains.

Age Factors↗