Functional genomics of the parasitic habits of blowflies and botflies
Infestation by dipterous larvae - myiasis - is a major problem for livestock industries worldwide and can cause severe economic losses. The Oestroidea superfamily is an interesting model to study the evolution of myiasis-causing flies because of the diversity of parasitism strategies among closely-related species. These flies are saprophagous, obligate parasites, or facultative parasites and can be subdivided into cutaneous, nasopharyngeal, traumatic, and furuncular. We expect that closely-related species have genetic differences that lead to the diverse parasitic strategies. To identify genes with such differences, we used gene expression and coding sequence data from five species (Cochliomyia hominivorax, Chrysomya megacephala, Lucilia cuprina, Dermatobia hominis, and Oestrus ovis). We tested whether 1,287 orthologs have different expression and evolutionary constraints under different scenarios. We found two up-regulated genes; one in species causing cutaneous myiasis that is involved in iron transportation/metabolization (ferritin), and another in species causing traumatic myiasis that responds to reduced oxygen levels (anoxia up-regulated-like). Our evolutionary analysis showed a similar result. In the Ch. hominivorax branch, we found one gene with the same function as ferritin that may be evolving under positive selection, spook. This is the first step towards understanding origins and evolution of parasitic strategy diversity in Oestroidea.