| Summary: | Purpose: Maternal effects are important drivers of evolutionary dynamics through expression of phenotypic plasticity in offspring. One form of maternal effects that is understudied is the impactof maternal stress hormones on offspring phenotype, especially in the context of lactation. We assessed phenotypic programming of immune development in response to maternal stress during lactation in wild Northern Elephant seal (Mirounga angustirostris) offspring. Methods: We induced an artificial stress response by administering repeated ACTH (adrenocorticotropic hormone) challenges in lactating mothers, and observed effects in offspring during the end of lactation and two weeks after weaning. We analyzed cortisol and a suite of immune markers comprising the innate and adaptive branches of the immune system. Once weaned, we measured immune response to a novel antigen, Keyhole Limpet Hemocyanin (KLH). Findings: Mothers transferred significant amounts of cortisol to pups in milk, resulting in highly elevated cortisol in our treatment group of Northern Elephant Seal (Mirounga angustirostris) pups. In contrast, treatment pups exhibited lower serum cortisol after weaning. Few immune markers showed alteration during suckling or weaning, except for reduced Immunoglobulin E (IgE) concentrations in treatment pups after weaning. By weaning, treatment pups experienced a lowered response of antibodies to KLH. Conclusion: This study is the first to use an immune test on a marine mammal, and shows it may be critical in assessing immune function. These results suggest maternal cortisol transfer via lactation has the ability to modulate offspring phenotype in both immune and HPA axis response.
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