Cytotaxonomic and molecular analysis of Simulium (Edwardsellum) damnosum sensu lato (Diptera: Simuliidae) from Abu Hamed, Sudan

Abstract

The northernmost focus for Onchocerca volvulus Leuckhart (Nematoda: Onchocercidae), the causative agent of human onchocerciasis, is found along the Nile near the town of Abu Hamed in Sudan. The vector for O. volvulus at this focus is a single monomorphic population of Simulium (Edwardsellum) damnosum Theobald. This black fly population is limited to a small area between the fourth and fifth cataracts of the Nile River that is isolated geographically from all other populations of S. damnosum sensu lato. Phylogenies produced from cytological analyses and sequence data derived from the NADH dehydrogenase subunit 4 and 16S rRNA genes indicate that Abu Hamed black flies are similar to, but distinct from, the savanna-dwelling sibling species of S. damnosum s.l., Simulium (Edwardsellum) damnosum sensu strictu Theobald, and S. (Edwardsellum) sirbanum Vajime & Dunbar. The DNA sequence and the cytological data support the hypothesis that the black fly population present in Abu Hamed may represent a new sibling species of S. damnosum s.l. We propose that this population be informally designated as the hamedense form of the Simulium damnosum complex.