A new cytotype of Simulium squamosum from south‐west Cameroon

Abstract

A new cytotype of Simulium squamosum Enderlein (Diptera: Simuliidae) (here named S. squamosum'D') is described from around Mount Cameroon in south-west Cameroon on the basis of sex-chromosome differences on the short arm of chromosome I. Two polymorphic inversions, IS-To (a new inversion) and IS-2, are partially Y linked. These inversions usually occur together, although IS-To has a higher frequency and is more strongly Y linked than IS-2. This sex-chromosome system has not been previously described and the occurrence and evolution of sex-chromosome systems in S. squamosum is discussed.

Molecular systematics ofSimulium squamosum, the vector in the Kinsuka onchocerciasis focus (Kinshasa, Democratic Republic of Congo)

“…Although they found 1Ca associated with males only, the existence of both of these polymorphisms was reported by Henry and Meredith (1990), who also stated that the 1Ce polymorphism is unknown from any S. squamosum population other than that in the Kinshasa area. Therefore, the Kinshasa population is not identical to the subsequently reported cytotypes 'A-D' from Cameroon and Nigeria, which all lack 1Ce (Traore-Lamizana et al, 2001;Mustapha et al, 2004).…”

“…Although the Simulium species causing the biting nuisance 60 or 70 years ago was never identified, Henry and Meredith (1990) unequivocally identified S. squamosum in the Kinshasa region. Certain sex-differentiating features of the Kinshasa flies resembled, however, those of the cytotypes A, B, C, and D that were subsequently described from Cameroon and Nigeria (Traore-Lamizana et al, 2001;Mustapha et al, 2004). The primary goal of the present study was to re-establish the cytotaxonomic background for the Kinsuka population of S. squamosum.…”

“…Further east can be found a distinct subspecies -S. s. kitetense, from the eastern Democratic Republic of the Congo (Elsen and Post, 1989) -and the related 'Kagera' cytoform, on the Ugandan-Tanzanian frontier (Dunbar, 1966). To the north, S. squamosum occurs in Cameroon (Traore-Lamizana et al, 2001;Mustapha et al, 2004) and, represented by the 'Bioko' cytoform of the closely related species S. yahense, on the island of Bioko (Post et al, 2003). Other potential vectors of the S. damnosum complex have, however, been identified, by morphology, in and around Kinshasa, namely S. damnosum s.s. and S. sirbanum (Elsen et al, 1988).…”

“…Karyotypes were recorded using a Coolpix digital camera (Nikon Photo Products, Tokyo) attached to a compound microscope (Carl Zeiss, Oberkochen, Germany). The chromosomal banding patterns observed were compared with published chromosome maps (Vajime and Dunbar, 1975;Henry and Meredith, 1990;Mustapha et al, 2004).…”

Cytotaxonomy of Simulium soderense sp. nov. and a redescription of the ‘Kulfo’ form (Dunbar, 1969) of Simulium damnosum s.l. (Diptera: Simuliidae) as Simulium kulfoense sp. nov. in Ethiopia

“…Since the description of Simulium damnosum Theobald (Diptera: Simuliidae) as a species complex (Dunbar, 1966), around 60 cytoforms, some with formal scientific names, have been reported (Crosskey and Howard, 2004;Krü ger et al, 2004;Mustapha et al, 2004;Hadis et al, 2005;Krü ger et al, 2006b). The number of cytospecies is expected to rise as new areas are prospected.…”