Comparative descriptions of the pupae of five species of the <i>Culicoides imicola complex</i> (Diptera, Ceratopogonidae) from South Africa

Abstract

The viruses causing the economically important livestock diseases of African horse sickness (AHS) and bluetongue (BT) are transmitted by biting midges of the genus Culicoides (Diptera, Cerato po gonidae). In the Old World the most important vectors of these diseases are Culicoides imicola Kieffer, 1913, Culicoides brevitarsis Kieffer, 1917 and Culicoides bolitinos Meiswinkel, 1989. All three of these vectors belong to the Imicola complex of the subgenus Avaritia Fox, 1955. This species complex now comprises 12 sibling species; ten occur in sub-Saharan Africa and are difficult to identify (based mostly on subtle variations in the wing patterns) and so additional methods of reliable identification are needed. The pupal exuviae of the five commonest sibling species (C. imicola, C. bolitinos, Culicoides loxodontis Meiswinkel, 1992, Culicoides tuttifrutti Meiswinkel, Cornet &amp; Dyce, 2003 and Culicoides sp. # 107) harvested from a variety of large herbivore dung types and from decaying fruits, are described and illustrated in detail. It is shown that they can be differentiated clearly on a number of morphological characters and, furthermore, are separable into two distinct groups based (principally) on the shape of the respiratory organ. A key for identifying and differentiating these five pupae is provided. Also, the pupa of the Oriental-Australasian C. brevitarsis was compared with its allopatric sister taxon, C. bolitinos. Because they share a common larval habitat (cattle and buffalo dung) and are almost inseparable in the adult phenotype, the question of their possible synonymy is raised. However, their respective pupae could not be differentiated on gross morphology and so it is argued that this unresolved problem requires a molecular solution.

Insight on the larval habitat of Afrotropical Culicoides Latreille (Diptera: Ceratopogonidae) in the Niayes area of Senegal, West Africa

“…In the Afrotropical region where AHSV is endemic, larval habitats of Culicoides are almost unknown or require an update except for the southern part of the continent where Culicoides larval habitats are much investigated [14, 16, 19]. …”

“…Therefore, in the Afrotropical region, favorable larval habitats of C. imicola , the main vector species of AHSV and BTV, are only well described from South Africa. Apart from C. imicola , larval habitats of other Afrotropical species were investigated mostly in South Africa [14, 16, 18, 19], Zimbabwe [35] Nigeria [12] and Kenya [15]. These larval habitats can be grouped into four main types: (i) moist soil enriched greater or lesser in organic matter (decomposing plant matter, varying from intact material to humus, or of decomposed dung, such as is often found on irrigated pastures) with a great diversity of associated species [12, 15, 16, 18]; (ii) tree holes and other natural cavities in rotting wood, with often rare species such as C. accraensis , C. inornatipennis , C. clarkei , C. confusus , C. eriodendroni , C. nigripennis , C. olyslageri and C. punctithorax [16, 18]; (iii) dung pats of large herbivores such as African buffalo and cattle; and (iv) rotting fallen fruits of the sausage tree.…”

Phylogenetic relationships and molecular delimitation of CulicoidesLatreille (Diptera: Ceratopogonidae) species in the Afrotropical region: interest for the subgenus Avaritia

“…Some of their works include taxonomic identification keys for adults. Meiswinkel described or redescribed and compiled an identification key for adults and immature stages for the species of the Culicoides imicola group (Meiswinkel, ; Nevill et al ., ). Therefore, until all species have been compared molecularly as well as morphologically, it remains up to individual authors to either use the current published subgeneric classification by Borkent or the species groups (Labuschagne, ).…”

DNA barcoding and surveillance sampling strategies for Culicoides biting midges (Diptera: Ceratopogonidae) in southern India

“…Similar investigations are required to explore the potential cryptic diversity identified between the Indian and Australian specimens of C. brevitarsis . There is no evidence that the morphologically indistinguishable C. bolitinos [26, 90] is present in southern India as this species is genetically distinct from the Indian C. brevitarsis (mean sequence difference compared to South African C. bolitinos : 12.2 %; range: 11.6–12.6 %) . The Indian C. brevitarsis is also genetically distinct (mean sequence difference: 11.1 %; range: 10.6–11.5 %) from C. bolitinos specimens recently collected in Reunion Island (GenBank: KF186129 and KF186130) [91], which have been provisionally identified as C. bolitinos , but which have been shown to be genetically distinct from South African C. bolitinos (mean sequence difference: 6.4 %; range 5.6–6.9 %).…”