Although parasites represent a major component of biodiversity, they remain poorly assessed, especially in remote regions. In this study, we screened 461 reptiles from Socotra, the largest and most biologically diverse archipelago in Arabia. Using 18S rRNA primers, we detected various apicomplexan parasites, namely haemogregarines, sarcocystids and eimeriids. Haemogregarines were the most common and genetically diverse, followed by sarcocystids (genus Sarcocystis) and eimeriids (genera Isospora and Lankesterella). All were related to parasites of other reptiles, including species from Arabia, Northern Africa and Asia. Like their 29 endemic reptile hosts, almost all Socotran parasites presented high genetic divergence and ecological differences from those found elsewhere, and probably represent undescribed endemic species. Among hosts, skinks were the most parasitized, which contrasted with similar studies from other areas, probably due to their more generalist diet and habitat use. As expected due to its high species richness, geckos harboured the highest parasite diversity in the archipelago. Parasite diversity also seemed to be correlated to island size, as the largest island harboured most haplotypes. This study emphasizes the importance of screening parasites in wild hosts from remote regions and of considering host ecology to understand disease transmission across taxa.

Haemogregarines (Apicomplexa: Adeleiorina) are a diverse group of haemoparasites reported from almost all vertebrate classes. The most commonly recorded haemogregarines to parasitize anurans are species of Hepatozoon Miller, 1908. To date 16 Hepatozoon species have been described from anurans in Africa, with only a single species, Hepatozoon hyperolli (Hoare, 1932), infecting a member of the Hyperoliidae. Furthermore, only two Hepatozoon species are known from South African anurans, namely Hepatozoon theileri (Laveran, 1905) and Hepatozoon ixoxo Netherlands, Cook and Smit, 2014, from Amietia delalandii (syn. Amietia quecketti) and three Sclerophrys species, respectively. Blood samples were collected from a total of 225 individuals representing nine hyperoliid species from several localities throughout northern KwaZulu-Natal, South Africa. Twenty frogs from three species were found positive for haemogregarines, namely Afrixalus fornasinii (6/14), Hyperolius argus (2/39), and Hyperolius marmoratus (12/74). Based on morphological characteristics, morphometrics and molecular findings three new haemogregarine species, Hepatozoon involucrum Netherlands, Cook and Smit n. sp., Hepatozoon tenuis Netherlands, Cook and Smit n. sp. and Hepatozoon thori Netherlands, Cook and Smit n. sp., are described from hyperoliid hosts. Furthermore, molecular analyses show anuran Hepatozoon species to be a separate monophyletic group, with species isolated from African hosts forming a monophyletic clade within this cluster.

Understanding the processes that shape parasite diversification, their distribution and abundance provides valuable information on the dynamics and evolution of disease. In this study, we assessed the diversity, distribution, host-specificity and infection patterns of apicomplexan parasites in amphibians and reptiles from Oman, Arabia. Using a quantitative PCR approach we detected three apicomplexan parasites (haemogregarines, lankesterellids and sarcocystids). A total of 13 haemogregarine haplotypes were identified, which fell into four main clades in a phylogenetic framework. Phylogenetic analysis of six new lankesterellid haplotypes revealed that these parasites were distinct from, but phylogenetically related to, known Lankesterella species and might represent new taxa. The percentage of infected hosts (prevalence) and the number of haemogregarines in the blood (parasitaemia) varied significantly between gecko species. We also found significant differences in parasitaemia between haemogregarine parasite lineages (defined by phylogenetic clustering of haplotypes), suggesting differences in host–parasite compatibility between these lineages. For Pristurus rupestris, we found significant differences in haemogregarine prevalence between geographical areas. Our results suggest that host ecology and host relatedness may influence haemogregarine distributions and, more generally, highlight the importance of screening wild hosts from remote regions to provide new insights into parasite diversity.

The effect of haemoparasites on the physiology and behaviour traits of their hosts was examined using Haemogregarina sp., a parasite of the common lizard, Lacerta vivipara, from the south of France. Infection with haemogregarines was associated with a reduced haemoglobin concentration and an increased number of immature red blood cells. Parasitized individuals also showed a reduced oxygen consumption at rest and a lower locomotor speed. We also found that the multiplication rate of the parasite depended on the temperature at which the lizard was maintained. Between 21 and 28 °C the multiplication rate of the parasite was significantly lower than between 29 and 35 °C. This suggests that the parasites may suffer reproductive costs when hosts reduce their body temperature.