Host age modulates within-host parasite competition.

In many host populations, one of the most striking differences among hosts is their age. While parasite prevalence differences in relation to host age are well known, little is known on how host age impacts ecological and evolutionary dynamics of diseases. Using two clones of the water flea Daphnia magna and two clones of its bacterial parasite Pasteuria ramosa, we examined how host age at exposure influences within-host parasite competition and virulence.

Host age modulates parasite infectivity, virulence and reproduction.

Host age is one of the most striking differences among hosts within most populations, but there is very little data on how age-dependent effects impact ecological and evolutionary dynamics of both the host and the parasite. Here, we examined the influence of host age (juveniles, young and old adults) at parasite exposure on host susceptibility, fecundity and survival as well as parasite transmission, using two clones of the water flea Daphnia magna and two clones of its bacterial parasite Pasteuria ramosa. Younger D.

Threat detection: behavioral practices in animals and humans.

In contrast to a perceptible threat that releases freezing, fleeing and fighting, abstract potential threat elicits anxiety and vigilance. The prevalent view is that the larger the animal groups the lower the individual vigilance. Vigilance is a reflection of anxiety, and here we show that anxiety is contagious in grouped social animals.

Together they stand: A life-threatening event reduces individual behavioral variability in groups of voles.

In the present study, voles were exposed to owl attack as a group, with their cage mates and in their familiar cages. The anxiety level of each vole was assessed using two parameters: time spent in the open arm of an elevated plus maze; and time spent away from the walls of an open field. Each parameter was measured 24h before and after the group exposure to the owls.