PubMed · 15318448
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
2004. Disruptive physicians.. https://pubmed.ncbi.nlm.nih.gov/15318448/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Lanchester's models of attrition describe casualty rates during battles between groups as functions of the numbers of individuals and their fighting abilities. Originally developed to describe human warfare, Lanchester's square law has been hypothesized to apply broadly to social animals as well, with important consequences for their aggressive behaviour and social structure. According to the square law, the fighting ability of a group is proportional to the square of the number of individuals, but rises only linearly with fighting ability of individuals within the group. By analyzing mortality rates of fire ants (Solenopsis invicta) fighting in different numerical ratios, we provide the first quantitative test of Lanchester's model for a non-human animal. Casualty rates of fire ants were not consistent with the square law; instead, group fighting ability was an approximately linear function of group size. This implies that the relative numbers of casualties incurred by two fighting groups are not strongly affected by relative group sizes and that battles do not disproportionately favour group size over individual prowess.
Glutathione is the major non-protein thiol to which many different roles in the central nervous system (CNS) are attributed. To further investigate the glutathione response in the CNS, we tested the effect of three stress models on glutathione levels in the brain. We tested the effect of two models of repeated intraspecific agonistic interaction in mice. No influence was observed over the glutathione levels in the mice cerebral cortex, cerebellum, liver, and blood. Acute restraint stress in rats was found to induce an increase in glutathione levels in the cerebellum after 2 and 4 h of immobilization, an effect not observed in the cerebral cortex, striatum, and hippocampus. To investigate the interference of an inhibitor of nitric oxide synthase (NOS), N(omega)Nitro-L-arginine-methyl-ester (L-NAME, 50 mg/kg) was applied i.p. at the beginning of restraint stress. L-NAME alone did not lead to a change in glutathione levels although, in combination with restraint stress, it induced an increase in such levels. This effect was observed in all four structures studied, i.e. cortex, hippocampus, striatum, and cerebellum. The values returned to basal levels after 6h of immobilization. In conclusion, the pattern of dominance, after repeated intraspecific agonistic interaction, was ineffective in producing alterations in brain glutathione, whereas acute restraint stress led to an increase in glutathione levels within a window of 2-4 h, and the inhibition of NOS increased glutathione levels in all studied rat brain structures, suggesting a specificity interference of acute restraint stress with the glutathione system.
Because of pelagic-larval dispersal, coral-reef fishes are distributed widely with minimal genetic differentiation between populations. Amphiprion akallopisos, a clownfish that uses sound production to defend its anemone territory, has a wide but disjunct distribution in the Indian Ocean. We compared sounds produced by these fishes from populations in Madagascar and Indonesia, a distance of 6500 km. Differentiation of agonistic calls into distinct types indicates a complexity not previously recorded in fishes' acoustic communication. Moreover, various acoustic parameters, including peak frequency, pulse duration, number of peaks per pulse, differed between the two populations. The geographic comparison is the first to demonstrate 'dialects' in a marine fish species, and these differences in sound parameters suggest genetic divergence between these two populations. These results highlight the possible approach for investigating the role of sounds in fish behaviour in reproductive divergence and speciation.