|Haemogregarines are Apicomplexan parasites only distantly related to the malaria parasites. Haemogregarines are very common in reptile hosts. We have found them in lizards from very wet habitats (west Africa where perhaps five species were found in the rainbow lizards in Sierra Leone) to very dry deserts (the Gobi in northern China). We have also found Haemogregarines in crocs in South America. The life cycles of these parasites can be very complex and diverse. Proper description and identification of Haemogregarines requires knowledge of the full life cycle, and thus the real diversity of the parasites is unknown. In fact, the Haemogregarines may be regarded as among the poorest known common parasites of vertebrates. Note the diversity of shapes seen in the photos above and the variation in how the parasites may displace the host cell nucleus. The most general impression of these parasites is of a cigar or sausage-shaped cell, with the red or purple staining nucleus as a band in the middle. Perkins and Keller (Journal of Parasitology) provide one of the first molecular phylogenies of a small number of species of Haemogregrines.
Infections can have high parasitemia, and so we might expect the parasite to harm the lizard host. An early study (Schall, 1986, Journal of Parasitology) found no harm to the endemic whiptail lizard of Aruba island. Far more detailed studies in Australia and Europe have now found that Haemogregarines can be an important factor in the ecology and behavior of lizard hosts.