A deeper look at Set8: Apicomplexa, animals and slime molds. A phylogenetic analysis with only animal, apicomplexan and slime mold Set8. Set8 from Apicomplexa, nematodes and arthropods strongly group together (0.81 posterior probability) in a sub-clade apart from vertebrates. A Set8 ortholog from an animal, the parasitic nematode Trichinella spiralis, groups with strong Bayesian posterior probability with the Apicomplexans orthologs. Similarly, soil nematodes group with the soil-based slime mold Dictyostelium, implying a horizontal gene transfer event in this taxon as well. These proposed events are denoted by black arrows. As all apicomplexans studied feature Set8, the most likely scenario is a horizontal gene transfer to an ancestral apicomplexan.