Simplified view of sex-determining pathways in the branchiopod crustacean Daphnia and insects.

An ESD pathway in Daphnia is compared with GSD pathways in insect model species, honeybee (Apis mellifera [64]), Mediterranean fruit fly (Med. fly, Ceratitis capitata, [62]) and fruit fly (Drosophila melanogaster [78]). Conserved Doublesex and Transformer homologs are indicated with red and blue boxes, respectively. Phylogenetic relationships among the four species are shown above the pathways [42], [64], [71]. CSD, complementary sex determiner; fem, feminizer; Am, Apis mellifera: Cc, Ceratits capitata; sxl, sex lethal; mya, million years ago.