PARASITES AND THE AVIAN SPLEEN - HELMINTHS

A comparative analysis of the relationship between the spleen-a major organ of immunity-and helminths was undertaken with bird species, usin g the phylogenetic regression technique. Species in which many individ uals are infected with nematodes relative to the number of individuals examined for the presence of helminths (termed 'relative nematode pre sence') have significantly larger spleens, for a given body weight, in females (though not in males). There was little indication that this relationship depends on incidental ecological indices, the weights of other organs, or the 'relative presences' of trematodes, cestodes or h aematozoa. Combined with previous, experimental, work it suggests that the avian spleen is important in resisting nematodes. Body weight is correlated with the relative presence of helminths; but even after rem oving body size effects, bird species which tend to be infected with t rematodes are also more likely to be infected with cestodes. This pape r indicates that the spleens of wild bird species are associated with macroparasites in the natural environment.