Hepatozoon Gamonts in Focus: New Insights on Morphometrics, Ultrastructural Features, and Cytopathological Effects of H. annularis and H. rawashi from their Heavily Infected Geckonid Hosts

The morphological and ultrastructural characteristics of Hepatozoon annularis and H. rawashi (Apicomplexa: Hepatozoidae), which infect two gecko species (Tarentola annularis and Ptyodactylus hasselquistii) in Egypt, were thoroughly investigated. Parasitemia levels reached up to 40 % for H. annularis and 20 % for H. rawashi. Several key morphometric parameters were measured, including nuclear/body area and nuclear/cytoplasmic area, for the gamonts of both species. Uninfected erythrocytes and single and double gamont-infected erythrocytes were also analysed. The study revealed notable structural changes in the infected cells, such as nuclear fragmentation and a progressive increase in cytoplasmic consumption. Transmission electron microscopy (TEM) revealed distinct ultrastructural features, including trilaminate membranes, apicomplexan organelles, and electron-dense nuclear heterochromatin. H. annularis exhibited micropores and membrane invaginations, which may play a role in parasite-host interactions, whereas H. rawashi showed dense granule accumulations and an elongated membrane protrusion, potentially facilitating host cell entry. Additionally, a unique membranous organelle has been observed in H. rawashi. These findings provide new insights into the cellular adaptations of these Hepatozoon species and their interactions with the host, contributing to the understanding of host-parasite dynamics.