Taxonomy and molecular taxonomy

Abstract

Cryptosporidium parasites belong to the phylum Apicomplexa and possess features of both the coccidia and gregarines. Currently, 25 species of Cryptosporidium are recognized in fish, amphibians, reptiles, birds and mammals. All 25 species have been confirmed by morphological, biological, and molecular data. Cryptosporidium duismarci and C. scophthalmi lack sufficient biological and/or molecular data to be considered valid species. In addition to the named species, more than 40 genotypes from various vertebrate hosts have been described. For these genotypes to receive taxonomic status, sufficient morphological, biological, and molecular data are required and names must comply with the rules of the International Code for Zoological Nomenclature (ICZN). A different interpretation of the ICZN led to the proposal that Cryptosporidium parvum be renamed as Cryptosporidium pestis and that C. parvum be retained for C. tyzzeri. However, this proposal violates the guiding ICZN principle of maintaining taxonomic stability and avoiding confusion. In addition, C. pestis lacks a full taxonomic description and therefore is not a valid species. The taxonomic status of Cryptosporidium spp. is rapidly evolving and many genotypes are likely to be formally described as species in the future.