Parental investment and life history theories predict that long-lived parents facing pathogenic stress should divert energy away from reproduction and redirect that energy towards coping with the imminent threat of disease. After generating a successful immune response, parents can revert to investing in reproduction. Although termite queens can sustain offspring quality in the face of disease, the consequences of pathogenic stress on the king’s reproductive investment have not been quantified.
Termite kings were allocated to four treatments to assess reproduction costs in response to disease: naïve, saline injection (controls), heat-killed Serratia (bacterial vaccine) injection, or live Serratia injection. They were then paired with a naïve queen. Twenty-one days post-pairing, the testes of these kings were dissected, photographed, and their surface area estimated. Total protein content as a function of paternal treatment was also quantified. Additionally, testes were assayed for their antibacterial properties against Serratia. If live Serratia-injected kings traded reproduction for personal immunity, then testes size should be smaller, and protein content should be lower than those of controls. Moreover, the testes protein profiles of live Serratia-injected kings should differ relative to controls. Finally, testes of live Serratia-injected kings should reduce the growth of the pathogen compared to controls.
Contrary to expectation, testes size is not affected by exposure to Serratia. Additional assays are currently underway. Focusing on how kings respond to disease exposure in terms of reproductive investment, can help explain the physiological “decisions” animals make in nature: invest in immunity or reproduction?