ИСТИНА

After invading a vertebrate host, parasites elicit a shift in metabolic priorities within the host, forcing it to reallocate its energy resources between an immune response and other life-history traits. Malarial parasites (Plasmodium, Haemosporida) proliferate in red blood cells and destroy them after releasing merozoites from infected cells. These processes may cause oppositely directed results: an increase of metabolic rate due to the immune response demand or its decrease because of the lower oxygen-binding capacity of blood. It is well known that long host-parasite coevolution may alter the extent of damage to the host’s organism. In our study, two groups of juvenile siskins (Spinus spinus) were infected: one with locally transmitted Plasmodium relictum (lineage SGS1) and second with an African P. ashfordi (GRW2). We used flow-through respirometry to measure resting metabolic rate (RMR) of infected siskins. We found a significant relationship between RMR and number of days post infection in both groups. After one-week post infection, RMR of all experimental birds decreased. However, by the next measurement there was a sharp increase in RMR followed by a further slight increase, which continued until the end of the experiment. Birds from the group infected with P. ashfordi had higher RMR compared with the birds from P. relictum group. Birds having initially high RMR tended to reduce it, while individuals with low initial RMR tended to increase it. It seems that malarial parasite, new to the host, causes mobilization of energy resources in naïve birds, which may lead to a rapid depletion and even death. The study has been funded by Russian Science Foundation (20-14-00049).