Immune measures
Immune measures (circulating hemocytes, presence of microaggregations, antibacterial activity) of 137 males were taken immediately after calling effort trials (sample sizes for diet type and infection cue dose included in appendix table A1). Prior mortality resulting from diet and infection cue treatments limits our interpretation of these data.
Neither diet type (χ2 1,131 = 2.275; p = 0.1315) nor infection cue (χ2 4,131 = 2.533; p = 0.6387) significantly influenced the number of circulating hemocytes; the nonsignificant interaction between diet and infection cue (χ2 4,124 = 5.421; p = 0.2468) was removed from analysis. However, the presence of circulating microaggregations of hemocytes was significantly influenced by both pronotum width (χ2 1,123 = 4.237; p = 0.0396) and the interaction between diet type and infection cue (χ2 4,123 = 10.472; p = 0.0332). Larger males were more likely to have circulating microaggregations (see appendix Fig. A1). Males fed on the high carbohydrate diet were less likely to have circulating microaggregations if they received the high infection cue dose, and this also tended to be true for males fed the high protein diet and receiving a moderate infection cue dose (Fig. A1).
For antibacterial activity of hemolymph, we found a nonsignificant trend for infection cue to affect the zone of growth inhibition of M. luteus (F4,125 = 2.293; p = 0.0631), with antibacterial activity lowest at the high infection cue dose (estimated marginal means ± standard error: naive = 2.248 ± 0.487, sham = 1.457 ± 0.322, low = 1.567 ± 0.326, moderate = 2.189 ± 0.490, high = 0.944 ± 0.218). However, diet type did not significantly influence antibacterial activity (F1,125 = 0.9194; p = 0.33949; estimated marginal means ± standard error: high protein = 1.66 ± 0.251, high carbohydrate = 1.41 ± 0.172).