The cactophilic Drosophila system of the Sonoran Desert is an excellent model not only to study how organisms process toxins, but how some taxa have evolved to rely on toxic compounds. Cacti contain toxic compounds that protect them from herbivory. When a cactus is injured, sap exudes from wounds, and microorganisms quickly colonize the sap and begin the decomposition process. Several Drosophila species feed and reproduce on necrotic tissue of columnar cacti.
While many members of the cactophilic Drosophilarepleta species group have been able to transition seamlessly onto a standard cornmeal diet, Drosophilamettleri is an exception. This is the only known species to breed exclusively in soil soaked with necrotic cactus. This taxon requires cactus-supplemented media to maintain healthy cultures under laboratory conditions.
Our understanding of the physiological processes required for Drosophila to utilize decomposing cactus as a host plant is limited. For example, we currently do now know whether D. mettleri derives nutritional benefit from the decomposing cactus, the saprophytic microorganisms present during decomposition, or a combination of the two. This study examines D. mettleri to understand how various life stages perform when reared on (1) standard media, (2) standard media + cactus powder, and (3) standard media + sterilized cactus powder. Development times at each life stage and the physical effects of nutrition on development, such as wing, head, and thorax size, were examined. The results show that the cactus has an essential role in ensuring that Drosophila survive the pupation and eclose successfully.
