Figure 3.
Development of mycosis (Metarhizium brunneum) in melanic (M) and non-melanic (NM) morphs of Galleria mellonella larvae after topical inoculation. The survival of each insect morph was recorded over 12 days following exposure to two doses of M. brunneum conidia. LС30 values demonstrate similar mortality levels of M and NM larvae in the presence of 107 conidia (p < 0.01, **) and 105 conidia (p < 0.001, ***), respectively (n = 60). The numbers of conidia per 0.25 mm2 cuticle were counted on M and NM morphs during infection with M. brunneum (107) (b), and the percentage of germinating conidia (c) that successfully adhered (*** = p < 0.001; n = 22). Penetration of the integument by germinating conidia led to the formation of melanotic lesions (white arrows) on NM larvae – representing de novo synthesis of melanin (d). Conversely, the pattern of melanin deposition on M larvae remained unchanged (e), indicating the melanic-defenses are preformed (images were taken 24 h.p.i. with 107 conidia).