New insights into the systematics of the AfrotropicalAmblyomma marmoreumcomplex (Acari, Ixodidae) and a novelRickettsia africaestrain using morphological and metagenomic approaches

Abstract

AbstractTheAmblyomma marmoreumcomplex includes some Afrotropical species, such asAmblyomma sparsum, a three-host tick that parasitizes reptiles, birds, and mammals, and is a recognized vector ofEhrlichia ruminatum. However, the lack of morphological, genetic and ecological data onA. sparsumhas caused considerable confusion in its identification amongA. marmoreumcomplex members. In this study, we used microscopy and metagenomic approaches to analyzeA. sparsum ticks collected from a puff adder snake (Bitis arietans) in southwest Senegal (an endemic rickettsioses area) in order to supplement previous morphological descriptions, provide novel genomic data for theA. marmoreumcomplex, and search for some associated spotted fever agent. Based on stereoscope and scanning electron microscopy (SEM) morphological evaluations, we provided high-quality images and new insights about punctation and enameling in the male ofA. sparsumto facilitate identification for future studies. Additionally, the metagenomic approach allowed us assembly the complete mitochondrial genome ofA. sparsum, as well as the nearly entire chromosome and complete plasmid sequences of a novelRickettsia africaestrain. Phylogenomic analyses showed a close relationship betweenA. sparsumandA. nuttallifor the first time and confirmed the position ofA. sparsumwithin theA. marmoreumcomplex. Our results provide new insights into the systematic ofA. sparsumandA. marmoreumcomplex, as well as the genetic diversity ofR. africaein Afrotropical region. Future studies should consider the possibility thatA. sparsummay be a competent vector forR. africae.