PARASITISM, IMMUNE-RESPONSE AND REPRODUCTIVE SUCCESS IN THE HOUSE MARTIN DELICHON URBICA

Parasites often exert strong selection pressures on their hosts that h ave evolved anti-parasite defences to counter the negative effects of parasites. Wie studied the relationship between intensity of parasitis m, one aspect of host immune response, and host reproductive success, using the house martin bug Oeciacus hirundinis and its house martin De lichon urbica host as a model system. Experimental manipulation of par asite load of nests during laying of the first clutch altered the inte nsity of parasitism. Parasites reduced the reproductive success of the ir-hosts measured in terms of body condition and survival of nestlings . Host immune response, measured as the concentration of gammaglobulin s and total plasma proteins, was positively associated with parasite r eproduction. estimated as the number of juvenile parasites, but was on ly weakly related to the intensity of adult parasites. The concentrati on of gammaglobulins was negatively related to nestling body mass, imp lying a trade-off between immune function and body condition, Parasite reproduction thus exerts a cost on hosts by increasing the immune res ponse.