parasites: suborder Adeleorina—eight genera suborder Haemosporina—all genera in this suborder suborder Eimeriorina—two genera (Lankesterella and Schellackia) Within the Adelorina are species that infect invertebrates and others that infect vertebrates. The Eimeriorina—the largest suborder in this phylum—the lifecycle involves both sexual and asexual stages. The asexual stages reproduce by schizogony. The male gametocyte produces a large number of gametes and the zygote gives rise to an oocyst, which is the infective stage. The majority are monoxenous (infect one host only), but a few are heteroxenous (lifecycle involves two or more hosts). The number of families in this later suborder is debated, with the number of families being between one and 20 depending on the authority and the number of genera being between 19 and 25. Taxonomy History The first Apicomplexa protozoan was seen by Antonie van Leeuwenhoek, who in 1674 saw probably oocysts of Eimeria stiedae in the gall bladder of a rabbit. The first species of the phylum to be described, Gregarina ovata in earwigs intestines, was named by Dufour in 1828. He thought that they were a peculiar group related to the trematodes, at that time included in Vermes. Since then, many more have been identified and named. During 1826–1850, 41 species and six genera of Apicomplexa were named. In 1951–1975, 1873 new species and 83 new genera were added. The older taxon Sporozoa, included in Protozoa, was created by Leuckart in 1879 and adopted by Bütschli in 1880. Through history, it grouped with the current Apicomplexa many unrelated groups. For example, Kudo (1954) included in the Sporozoa species of the Ascetosporea (Rhizaria), Microsporidia (Fungi), Myxozoa (Animalia), and Helicosporidium (Chlorophyta), while Zierdt (1978) included the genus Blastocystis (Stramenopiles). Dermocystidium was also thought to be sporozoan. Not all of these groups had spores, but all were parasitic. However, other parasitic or symbiotic unicellular organisms were included too in protozoan groups outside Sporozoa (Flagellata, Ciliophora and Sarcodina), if they had flagella (e.g., many Kinetoplastida, Retortamonadida, Diplomonadida, Trichomonadida, Hypermastigida), cilia (e.g., Balantidium) or pseudopods (e.g., Entamoeba, Acanthamoeba, Naegleria). If they had cell walls, they also could be included in plant kingdom between bacteria or yeasts. Sporozoa is no longer regarded as biologically valid and its use is discouraged, although some authors still use it as a synonym for the Apicomplexa. More recently, other groups were excluded from Apicomplexa, e.g., Perkinsus and Colpodella (now in Protalveolata). The field of classifying Apicomplexa is in