Alteration of the Pathogenicity of Pasteurella pneumotropica for the Murine Lung Caused by Changes in Pulmonary Antibacterial Activity

Pasteurella pneumotropica is a potential pulmonary pathogen in mice. In healthy animals, this organism was killed rapidly by the normal function of the intrapulmonary phagocytic defense mechanisms. Impairment of this bactericidal activity by the acute renal failure of nephrectomy resulted in multiplication of the Pasteurella in the lung, both when the animals were nephrectomized first and then infected, and when the animals were infected first and nephrectomized several hours after the infection. The study demonstrates that the pathogenicity of the Pasteurella organisms is governed by the functional state of these pulmonary antibacterial mechanisms.     

Rapid development of cleaning behaviour by Torresian crows Corvus orru on non-native banteng Bos javanicus in northern Australia

In this paper we report the observation of a rapidly developed vertebrate symbiosis involving ectoparasite cleaning by a native corvid of northern Australia, the Torresian crow Corvus orru , on a recently introduced bovid ungulate, the banteng Bos javanicus . Facultative symbioses benefiting both participants (mutualisms) between birds and mammals appear to be rare, despite the apparent advantages obtained by the participants (ecto-parasite removal from the host and food provision to the cleaner). On three separate dates we observed a total of four C. orru individuals eliciting facilitation behaviours by a total of ten female banteng to assist in the removal of ectoparasites. Our observations document the first-known incidence of facultative cleaning behaviour by a native bird species on a non-native, wild vertebrate that has developed in approximately 150 years since the banteng's introduction to Australia.     

VARIABLE SELECTION ON EUROSTA'S GALL SIZE,I: THE EXTENT AND NATURE OF VARIATION IN PHENOTYPIC SELECTION

Natural fluctuations in environmental conditions are likely to induce variation in the intensity or direction of natural selection. A long-term study of the insect, Eurosta solidaginins Fitch (Diptera; Tephritidae), which induces stem galls on the perennial herb Solidago altissima (Asteraceae) was performed to explore the patterns of variation in phenotypic selection. The intensity of selection imposed by parasitoids and predators on gallmaking larvae, for gall size, was measured across 16 populations over the course of 4 generations, for a total of 64 population-generations. Directional selection was quantified by i, the selection intensity, and variance selection by j‘, a measure of the intensity of selection on phenotypic variance. Size-dependent attack by parasitoids caused upward directional selection (mean i_p = 0.42; SE = 0.023), while size-dependent bird attack favored larvae that induced smaller galls (mean i_b = -0.07; SE = 0.013. The mean net directional selection intensity was 0.35 (SE = 0.030), which indicates that insects inducing larger galls are generally favored by selection. The opposing patterns of size-dependent attack resulted in stabilizing selection in half the population generations, with an overall average. j‘ of -0.11 (SE = 0.078). The magnitude of directional selection was strongly influenced by the population mean gall size and weakly by the optimal gall size. The intensity of variance selection was strongly influenced by the shape of the fitness function, with sigmoidal and Gaussian-like shapes causing greater depletion of phenotypic variance.