Crowded locusts produce hatchlings vulnerable to fungal attack

Abstract

Transgenerational effects of parental experience on offspring immunity are well documented in the vertebrate literature (where antibodies play an obligatory role), but have only recently been described in invertebrates. We have assessed the impact of parental rearing density upon offspring disease resistance by challenging day-old locust hatchlings (Schistocerca gregaria) from either crowd- or solitary-reared parents with the fungal pathogen Metarhizium anisopliae var. acridum. When immersed in standardized conidia suspensions, hatchlings from gregarious parents suffered greater pathogen-induced mortality than hatchlings from solitary-reared parents. This observation contradicts the basic theory of positive density-dependent prophylaxis and demonstrates that crowding has a transgenerational influence upon locust disease resistance.

Figure 1.

(a,b) Pathogen challenge affects survivorship of hatchlings from both (a) solitarious and (b) gregarious parents. Solid black lines indicate control treatments and dashed red lines indicate pathogen treatments. Thin, flanking lines show standard errors. Fungal pathogens increase mortality in both groups, but the impact upon gregarious-parent insects is significantly greater (see table 1). (n = 51 gregarious; n = 228 solitarious; **p < 0.01; ***p < 0.001.)