Morphological and molecular identification of species of the Obsoletus group (Diptera: Ceratopogonidae) in Scandinavia

Abstract

After the introduction of bluetongue in northern Europe in 2006, populations of Culicoides have been monitored in many European countries. Large quantities of Culicoides specimens shall be determined to species, and it is thus important to find reliable morphological characters that are visualized in a stereomicroscope. Culicoides obsoletus, Culicoides scoticus, Culicoides chiopterus, and Culicoides dewulfi all belonging to subgenus Avaritia are common in collections in northern Europe. C. obsoletus and C. scoticus often make up more than 50% of the total catch of biting midges. Separation of the females of the four species by morphological characters has frequently been questioned, and in many cases, female specimens are grouped as an entity in veterinary and ecological studies. We show how it is possible using a stereomicroscope to separate the females of the four species by combining the shape of the third segment of the maxillary palp and the number and location of hairs on the first abdominal tergit. Validation of the quick stereomicroscope identification method was achieved by morphometric measurements and a molecular marker. In all cases, both methods verified the quick morphological species identification of the Obsoletus group females. In conclusion, the females of all four species of the Obsoletus group can be separated by a quick morphological method under the stereomicroscope.

Orientation behaviour of Culicoides obsoletus (Diptera: Ceratopogonidae), a relevant virus vector in northern Europe, toward host-associated odorant cues

“…Females of the two Obsoletus complex species were slide mounted and observed under a microscope (100-400× magnification) to distinguish them morphologically (Augot et al, 2010;Nielsen and Kristensen, 2011). Finally, specimens of the species C. obsoletus obtained in each iteration of the behavioural tests were counted.…”

Phenotypic differentiation and phylogenetic signal of wing shape in western European biting midges, Culicoides spp., of the subgenus Avaritia

“…As correct identification of disease vectors is essential in transmission risk assessment, recent efforts have centred upon developing molecular and morphological tools that allow a reliable discrimination between similar species of the Obsoletus group (Cêtre-Sossah et al, 2004;Pagès & Sarto i Monteys, 2005;Mathieu et al, 2007;Nolan et al, 2007;Augot et al, 2010;Nielsen & Kristensen, 2011). In spite of the advantages of employing morphometrics in cryptic species identification and the widespread use of this methodological approach in other biological disciplines, few studies have attempted to discriminate between similar species of Culicoides using multivariate analysis of continuous traits (exceptions are Pagès et al, 2009;Augot et al, 2010).…”

Molecular differentiation of Culicoides biting midges (Diptera: Ceratopogonidae) from the subgenus Culicoides Latreille in Denmark

“…To ensure correct species identification, studies were initiated to develop molecular tools to identify different species within the subgenera Avaritia and Culicoides. Species of these two subgenera include the most common species in Northern Europe and are expected to include some of the potential bluetongue disease vectors (Gomulski et al 2005;Pagès and Sarto i Monteys 2005;Nolan et al 2007;Mathieu et al 2007;Pagès et al 2009;Nielsen and Kristensen 2011).…”

“…Sorting and identification of biting midges were based on morphology, but the often high numbers of Culicoides specimens in samples led to an investigation of the potential of using molecular techniques for species identification and even for quantification of sample contents. COI barcodes as well as internal transcribed spacer 1 (ITS-1) sequences were available for the most abundant Danish species Culicoides obsoletus (Meigen 1818) and Culicoides scoticus Downes and Kettle 1952 from the subgenus Avaritia (Nolan et al 2007;Nielsen and Kristensen 2011). The subgenus Culicoides is the second most numerous subgenus found in black light samples from Denmark.…”