Morphological and molecular characterisation of the rhino-specific tick, Amblyomma rhinocerotis from South Africa

Abstract Ticks are hematophagous ectoparasitic arthropods that transmit pathogens to humans and animals worldwide. The Ixodidae are the largest family in the order Ixodida, and the genus Amblyomma is among the most diverse and widely distributed, occurring on all continents except Antarctica. In the Afrotropical region, Amblyomma species are of significant veterinary and public health concern, characterised by their large size, ornate appearance, and aggressive host-seeking behaviour. Amblyomma rhinocerotis is a host-specific tick associated with both black rhinoceroses ( Diceros bicornis ) and white rhinoceroses ( Ceratotherium simum ). Despite its ecological importance and close association with endangered hosts, it remains poorly studied. Prior to this study, knowledge of the species was limited to morphological descriptions of adult stages, with immature stages remaining undescribed. Molecular data are scarce, with only one partial 12S rRNA sequence available in GenBank. To address these gaps, the present study presents a comprehensive morphological characterisation of A. rhinocerotis across all developmental stages, together with molecular confirmation using the 12S rRNA, 16S rRNA, and COI genes. Detailed morphological descriptions of all stages were supported by high-resolution imaging and scanning electron microscopy, while molecular analyses were performed using the 12S rRNA, 16S rRNA, and cytochrome c oxidase subunit I genes. Maximum likelihood analyses were performed in MEGA12. Adult morphology was consistent with previous descriptions. Phylogenetic analyses showed strong support for the A. rhinocerotis monophyletic clade, with bootstrap values ranging from 84–100%, and all intraspecific genetic distances were lower than interspecific distances. This integrated morphological and molecular approach confirms A. rhinocerotis identity across developmental stages and reinforces the use of mitochondrial markers in tick systematics.