Authors

C A Cook¹; N J Smit¹;  ¹ North-West University, South Africa

Discussion

Haemogregarines are obligate endoparasitic intracellular protozoa found in the blood of a range of vertebrates. Haemogregarines have a heteroxenous life cycle that includes asexual development in the vertebrate host, and sexual development in the invertebrate haematophagous vector responsible for their transmission. Classification of genera is based on the development within the vector. However, in the absence of life cycle data, the identity and taxonomy of these becomes difficult, particularly when relying solely on morphological features of peripheral blood stages in the vertebrate host. In most cases these blood stages are all that is accessible and as such the majority of descriptions are based mainly on these. In the past decade, molecular characterisation of haemogregarines and the phylogenetic placement of the different genera have provided insight into these parasites’ generic relationships, assisting with taxonomy and insight into the potential vectors and modes of transmission. However, this is particular to those parasitising mammals, reptiles and amphibians. Not until recently has the same been attempted for those infecting fishes. Genera parasitising fishes include Babesiosoma and Dactylosoma (Dactylosomatidae), as well as Cyrilia, Desseria and Haemogregarina (sensu lato)(Haemogregarinidae). Recent research by Hayes and Smit (2019) on Haemogregarina (s.l.) bigemina represents the first molecular characterisation for any of the named haemogregarines of fishes.  Furthermore, these authors’ research suggests H. bigemina to fall outside of the “Haemogregarina” clade and altogether out of the Adeleorina, rather forming a separate apicomplexan marine clade. Building on this, current research into the molecular characterisation of further fish haemogregarines, of known and unknown identity, from Australia, the Caribbean, and South Africa, has followed a similar trend. As such, this brings into question the current identity and taxonomy of a number of haemogregarines of fishes, suggesting the possible need for a new genus and even family.