Melanotic masses are black nodules that form inside larvae and can be found in multiple mutants (Minakhina & Steward, 2006). There are two... Show moreMelanotic masses are black nodules that form inside larvae and can be found in multiple mutants (Minakhina & Steward, 2006). There are two types of melanotic masses, the immune-related masses and the non-hemocyte-associated masses (Minakhina & Steward, 2006). Immune-related melanotic masses form in lam mutants (Markovic et.al, 2009). We now show all lam mutant larvae survived and 33% of the them developed melanotic masses when grown on fresh food, however, only 66% of them survived and none of them formed melanotic masses when living in the frassfood; the mixture of poo medium collected from wild type larvae vials. We find that frassfood lethality is not recipe specific, since the results were similar on normal yeast mashed potato medium and Nutrifly food. Our results also identified that it is bacteria in frassfood that kills lam mutant larvae with melanotic masses because the survival and melanotic mass incidence of lam mutant larvae were similar to fresh food when antibiotics were added to frassfood. However lam mutant larvae with melanotic masses are not generally sensitive to bacteria because all lam mutant larvae showed sensitivity to S. marcescens. Besides, since there is no frassfood lethality observed on Relish mutants, we propose that the humoral response was not affected in the lam mutants. The frassfood lethality to larvae with melanotic masses was also observed in neither cactus mutants nor the hopTum-l mutants, so the immune defects that caused melanotic masses in these two mutants do not lead to the frassfood lethality. Finally, we show that the frassfood lethality is not exactly the same in lam overexpressing larvae with melanotic masses and lam C overexpressing larvae with melanotic masses to the lam/Df larvae with melanotic masses. Thus it is possible that the gut immunity was affected in lam mutants with melanotic masses so that they were killed by the bacteria in frassfood. M.S. in Biology, May 2012 Show less
