Trans-generational immune priming & sexual immune dimorphism across a parental care gradient in two fish families

Males and females have different life-history strategies due to the anisogamy of their reproductive elements. In conventional sex role species, female fitness is positively correlated with longevity, whereas males are selected for increasing mating rates. This is also reflected in the sexual immune dimorphism suggesting that females usually need a greater immune defence than females to efficiently fight parasites and pathogens. In addition, only females transfer immunity to their offspring due to both mechanistic and evolutionary constraints. In species with increased paternal care, these principles may fall. With higher paternal investment into offspring we hypothesize sexual immune dimorphism to be inverted: if paternal investment is higher, males should have a greater immune defence than females as now they are the limiting sex. In addition, if offspring are born in paternal environment, fathers should be selected to boost the offspring immune system as they will be exposed to similar parasite pressures. We want to investigate these evolutionary concepts in two fish families with a parental investment gradient, Syngnathids and Cichlids. With extensive sampling and assessment of direct immune defence and immune genes we want to determine the immunocompetence of different species in the field to determine sexual immune dimorphism and the inducibility of immune defence dynamics. As a second goal we want to address the mechanistic hormonal basis of sexual immune dimorphism via both baseline measuring and experimental manipulation of the hormone level. We then want to investigate the generality of bi-parental immune priming in both cichlids and fish and evaluate the costs of maternal versus paternal immune priming. This will be done using cross-fostering approach and extensive breeding experiments. This project will enhance our understanding of selection pressures of immune defence evolution and determine the effect of parental care on immune defence dyamics and parasite defence.