Social immunity of the family: parental contributions to a public good modulated by brood size.

Social immunity refers to any immune defence that benefits others, besides the individual that mounts the response. Since contributions to social immunity are known to be personally costly, they are contributions to a public good. However, individuals vary in their contributions to this public good and it is unclear why.

Parents influence asymmetric sibling competition: experimental evidence with partially dependent young.

Asymmetric sibling competition, which occurs when some siblings hatch as stronger competitors than others, is an important component of avian reproductive strategies. Here, we report two experiments on the burying beetle Nicrophorus vespilloides investigating how parents might influence the outcome of asymmetric sibling competition. In this species, as in altricial birds, different-aged offspring compete for resources provided by the parents.

Influence of aqueous aluminium on the immune system of the freshwater crayfish Pacifasticus leniusculus.

Little is known of the effects of aluminium (Al) on invertebrate immunity despite the ubiquitous nature of the metal and its toxicity to aquatic organisms. Here we examine the effect of Al at neutral pH on the immune system of the freshwater crayfish Pacifasticus leniusculus. Heat-killed bacteria were injected at intervals into the haemolymph of crayfish continuously exposed to a sub-lethal concentration (500 microg l(-1)) of Al over 40 days.