Barcoding of the Genus Culicoides (Diptera: Ceratopogonidae) in Austria-An Update of the Species Inventory Including the First Records of Three Species in Austria

Molecular characterisation of common Culicoides biting midges (Diptera: Ceratopogonidae) in Ireland

BACKGROUND

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) act as vectors for several arboviruses, including bluetongue virus (BTV) and Schmallenberg virus (SBV), which affect livestock health and productivity. In Ireland, limited genetic data are available regarding the diversity of Culicoides species. This study represents the first attempt to characterise Culicoides in this region using molecular techniques.

METHODS

Adult Culicoides samples were captured using Onderstepoort Veterinary Institute (OVI) traps across six locations in Ireland. Subsequent molecular analyses involved polymerase chain reaction (PCR) and sequencing of the cytochrome oxidase subunit 1 (CO1) and the internal transcriber spacer (ITS) barcoding regions to obtain species identities. In addition, using both markers, we inferred the population genetic structure and potential colonisation pathways of Culicoides obsoletus sensu stricto (s. str.), the major vector species in Ireland.

RESULTS

DNA barcoding facilitated identification of 177 specimens. Eight common Culicoides species were identified through DNA barcoding of CO1 and ITS gene regions. The presence of putative vectors of bluetongue virus (BTV) and Schmallenberg virus (SBV) were also confirmed, including species in the subgenus Avaritia (C. obsoletus s. str., C. scoticus, C. chiopterus, and C. dewulfi) and subgenus Culicoides s. str. (C. pulicaris and C. punctatus). Phylogenetic analysis confirmed the relationship between these vector species and facilitated the placement of Culicoides spp. that could not be identified to species level through DNA barcoding. Haplotype network analysis of C. obsoletus showed that some haplotypes of these species are shared between Continental Europe, the UK, and Ireland, suggesting a possible incursion pathway for this vector.

CONCLUSIONS

DNA barcoding employing a combination of two barcodes, CO1 and ITS, proved effective in identifying Culicoides, especially species within the obsoletus complex, which are difficult to morphologically distinguish. Our findings also suggest that investigation of the population genetic structure of Culicoides spp. could be used to model the potential introduction routes of midge-borne pathogens into the country.

DNA barcoding and host blood meal identification of Culicoides Latreille (Diptera, Ceratopogonidae) from Malaysia

Mitochondrial cytochrome oxidase I (COI) sequences were used to determine the genetic diversity and species identification efficacy of Culicoides from Malaysia. In total, 100 COI sequences were obtained from 13 morphologically identified species. Intraspecific genetic divergence varied from 0.48 % in C. parahumeralis to 14.88 % in C. palpifer. However, most (8 of 13) had low (<3 %) intraspecific genetic divergence. Identification of these species based on best match (BM) and best close match (BCM) methods revealed a high efficiency of the COI sequences with 100 % and 99 % success for BM and BCM, respectively. Identification in the BOLD database revealed that 10 species were successfully determined and agreed with morphological identifications. There remained three taxa which were ambiguous (C. jacobsoni) or had no species level identity match (C. palpifer and C. flavescens). Phylogenetic analyses found that all Malaysian specimens were clustered with conspecifics except C. palpifer. Specimens of this taxon separated into two divergent clades, one with members of a BIN (BOLD:ADT9601) of C. palpifer whereas the other formed a novel genetic lineage. Molecular species delimitation identified the morphologically identified species of the Malaysian Culicoides in the respective species. The exceptions were two divergent lineages found in C. palpifer because they were treated as two different taxa. Molecular identification of the host blood meal source revealed that all were from water buffalo (Bubalus bubalis).

A DNA barcode library of Austrian geometridae (Lepidoptera) reveals high potential for DNA-based species identification

Situated in the Eastern section of the European Alps, Austria encompasses a great diversity of different habitat types, ranging from alpine to lowland Pannonian ecosystems, and a correspondingly high level of species diversity, some of which has been addressed in various DNA barcoding projects. Here, we report a DNA barcode library of all the 476 species of Geometridae (Lepidoptera) that have been recorded in Austria. As far as possible, species were sampled from different Austrian regions in order to capture intraspecific genetic variation. In total, 2500 DNA barcode sequences, representing 438 species, were generated in this study. For complete coverage of Austrian geometrid species in the subsequent analyses, the dataset was supplemented with DNA barcodes from specimens of non-Austrian origin. Species delimitations by ASAP, BIN and bPTP methods yielded 465, 510 and 948 molecular operational taxonomic units, respectively. Congruency of BIN and ASAP partitions with morphospecies assignments was reasonably high (85% of morphospecies in unique partitions), whereas bPTP appeared to overestimate the number of taxonomic units. The study furthermore identified taxonomically relevant cases of morphospecies splitting and sharing in the molecular partitions. We conclude that DNA barcoding and sequence analysis revealed a high potential for accurate DNA-based identification of the Austrian Geometridae species. Additionally, the study provides an updated checklist of the geometrid moths of Austria.

Approach to the pruritic horse

Pruritus in the horse may be due to several causes, the most common being a hypersensitivity response to salivary proteins in the Culicoides genera, which may coexist with atopic dermatitis, also known as an environmental allergy to pollens, molds, dust, storage mites, etc. Less common etiologies are food allergy and contact allergy, the latter often caused by owners applying various products to the skin. Other ectoparasites, such as Chorioptes mites, may also initiate pruritus. Secondary bacterial infections (usually Staphylococcus spp) may be pruritic in and of themselves. This article reviews the questions that need to be asked of owners to obtain a relevant history, always important for any organ system, but perhaps none more so than the skin. The various clinical findings such as alopecia and crusts and their location on the horse, diagnostic methods such as intradermal or serum testing for allergies, and subsequent hyposensitization are also discussed. Therapeutic options currently available for the potential underlying diseases, in particular for the hypersensitivity reactions to Culicoides spp or environmental allergens, are reviewed with the studies of hyposensitization over the last 40 years, as well as medications that may be effective. While the most common causes of pruritus in the horse are known, the current understanding of the pathophysiology still needs to be investigated, and consequently, the most effective treatments for those causes need to be improved. Newer research is discussed that may eventually add to the diagnostic and therapeutic options currently available for the pruritic horse.

Assigning Culicoides larvae to species using DNA barcoding of adult females and phylogenetic associations

Background

Orbivirus-induced hemorrhagic diseases cause high mortality in wild and captive white-tailed deer in North America. The role of different Culicoides species in Orbivirus transmission outside of areas of intensive animal production has not been established. At our study location, bluetongue virus (BTV) RNA-positive female Culicoides debilipalpis pools have been detected annually since 2012 when BTV transmission was noted in a captive deer herd. Identifying specific larval habitats of suspected vectors at active transmission sites is crucial both for identifying the source of the vectors and for subsequently planning intervention actions. Since C. debilipalpis larvae are known to develop in tree holes, this study was designed to use DNA barcoding to identify larvae collected from tree holes.

Methods

Adult female Culicoides were collected using light or emergence traps and morphologically identified to 11 species. Culicoides sonorensis were also obtained from a laboratory colony. Substrate was collected from tree holes and flooded with water to harvest floating larvae. Total DNA from three to seven adult females per species and 19 larvae was extracted. Two loci of the nuclear 18S ribosomal RNA (rRNA) gene, one locus each of the mitochondrial cytochrome oxidase subunit I (COI) gene and the nuclear 28S rRNA gene were amplified using loci-specific primers.

Results

All 61 adults were sequenced at each of the four loci under study. Since no single locus delineated all putative species and the COI locus yielded unreliable pseudogenes for two individuals of C. arboricola, sequences of all four loci were concatenated to maximize species separation and allow for larval association with identified adults. Sixteen larvae were clearly assigned to species based on DNA barcoding and phylogenetic results. Multiple larvae were assigned to each of the C. debilipalpis clade, the C. villosipennis clade, the C. arboricola clade and the C. nanus clade.

Conclusions

Of the approximately 62 species described in the southeast USA, 21 have now been barcoded and sequences are publicly available. In this study, we constructed a database composed of species-specific sequences of adult Culicoides and then identified larvae to species by matching their corresponding sequences with adults. Since Culicoides larvae are difficult to identify, using DNA barcoding to facilitate larval habitat surveys can be a valuable tool.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05479-1.

DNA Barcoding of genus Culicoides biting midges (Diptera: Ceratopogonidae) in the Brazilian Amazon

Culicoides biting midges are capable to transmit Oropouche virus, Bluetongue virus and Mansonella spp. This study aimed to assess the utility of DNA barcode as an alternative method in the Culicoides species identification. The study was conducted in Jamari National Forest. Biting midges were collected using HP light traps during four months, February, April, August and October, 2018. Insects were morphologically identified to the species level, and rest of the body were subjected to DNA extraction and PCR targeting a fragment of the cytochrome c oxidase subunit I (COI) gene, which were analyzed and deposited in GenBank. A phylogenetic gene tree was reconstructed using RAxML software, and the sequences were assigned at Molecular Operational Taxonomic Unit (MOTU) level by species delimitation algorithms. According to morphological approach, 18 species of 2 subgenera and 7 species groups were identified. A total of 191 new COI barcodes from 18 species were generated. Of these, fifteen species have been deposited for the first time in all datasets in the world. These sequences allowed the correct identification of 188 and 187 specimens according to the BM and BCM criteria, respectively. The intraspecific genetic distances ranged from 0 to 16.5%, while the interspecific ones ranged from 2.1 to 27.1%. The nominal species Culicoides glabellus and C. tetrathyris splitted into three and two MOTUs, respectively, except for mPTP, indicating a cryptic diversity in these species. Also, sequences of C. pseudodiabolicus formed two MOTUs using all algorithms, except for PTP and ABGD, suggesting the existence of two potential species. In contrast, some barcodes of C. quasiparaensis and C. paraensis merged into a single MOTU, which can be explained by the complex characteristics of the paraensis group, since these species have similar morphological characters. Here, we provided the first COI barcodes for biting midges in Rondônia and Brazil, and demonstrates that these are sufficient to discriminate between some species.

Blood meal analysis: host-feeding patterns of biting midges (Diptera, Ceratopogonidae, Culicoides Latreille) in Slovakia

Biting midges of the genus Culicoides are vectors of important pathogens affecting domestic and wild animals and have played a major role in the re-emergence of new outbreaks of bluetongue (BTV) and Schmallenberg (SBV) viruses in Europe. To determine vector-host specificity, trophic preference from blood meal analysis is of major importance in the surveillance of arthropod-borne diseases. Of 28,752 specimens collected, we identified 17 Culicoides species and investigated a total of 48 host sequences from the blood meals. Culicoides obsoletus/C. scoticus, C. dewulfi, C. pulicaris, C. lupicaris, C. punctatus, C. newsteadi, C. riethi, and C. furcillatus were found to feed on mammals (cattle, horses, and humans), birds (domestic chickens), small rodents (Apodemus flavicollis), and hares (Lepus europaeus). To our knowledge, this is the first study investigating trophic preferences of Culicoides spp. in Slovakia. This study demonstrated that Culicoides species are able to feed on domesticated host vertebrates as well as birds, rodents, and humans.

Genetic variation, DNA barcoding and blood meal identification of Culicoides Latreille biting midges (Diptera: Ceratopogonidae) in Thailand

Biting midges of the genus Culicoides Latreille are blood sucking insects of medical and veterinary importance. Many species are vectors of disease agents transmitted to humans and other animals. Therefore, rapid and accurate species identification is essential for appreciation of all aspects of these insects. In this study, DNA barcode efficacy and molecular identification of host blood sources were examined in biting midges from Thailand. A total of 203 barcoding sequences were obtained from 16 Culicoides taxa. Intraspecific genetic divergence varied from 0.28% to 9.90% for specimens collected in Thailand. Despite this high level of genetic variation, DNA barcode identifications in the Barcoding of Life Data System had a considerable success rate (90%). Phylogenetic analyses and distance-based species delimitation methods indicated the possibility of cryptic species in four taxa, namely, Culicoides actoni Smit, C. arakawae Arakawa, C. huffi Causey and C. jacobsoni Macfie. Further investigations will be required to examine the species status of these lineages. Host blood meal identifications from 42 blood engorged females of 10 Culicoides taxa revealed three animal hosts: chicken, cattle and buffalo. Most of this information agrees with previous knowledge but this is the first report of C. actoni, C. fulvus and C. huffi feeding on chicken.

Integrative Taxonomy of the Spinous Assassin Bug Genus Sclomina (Heteroptera: Reduviidae: Harpactorinae) Reveals Three Cryptic Species Based on DNA Barcoding and Morphological Evidence

Simple Summary

The assassin bugs (Heteroptera: Reduviidae) are one of the largest and morphologically most diverse families of true bug, having essential impacts on forest ecosystems as predators. The spinous reduviid genus Sclomina exhibits shape mimicry and protective coloration adapted to the spinous Rubus plant that they inhabit. The genus Sclomina shows gradual morphological variability, so its morphological classification is still unresolved, and its biology is almost unknown. In this study, DNA barcodes and morphological evidence were combined to accurately divide the species of a comprehensive collection sampled in South China and North Vietnam. We found three cryptic species. The biological information and mimicry behavior uncover their successive evolutionary survival strategies.

Abstract

Sclomina Stål, 1861 (Heteroptera: Reduviidae: Harpactorinae) is endemic to China and Vietnam, with only two species, Sclomina erinacea Stål, 1861 and Sclomina guangxiensis Ren, 2001, characterized by spinous body and dentate abdominal connexivum. However, due to variable morphological characteristics, Sclomina erinacea, which is widely distributed in South China, is possibly a complex of cryptic species, and Sclomina guangxiensis was suspected to be an extreme group of the S. erinacea cline. In the present study, we conducted species delimitation and phylogenetic analyses based on the mitochondrial cytochrome c oxidase subunit I (COI) gene sequences of 307 Sclomina specimens collected from 30 sampling localities combined with morphological evidence. The result showed that all samples used in this study were identified as five species: Sclomina guangxiensis is a valid species, and Sclomina erinacea actually includes three cryptic species: Sclomina xingrensis P. Zhao and Cai sp. nov., Sclomina pallens P. Zhao and Cai sp. nov., and Sclomina parva P. Zhao and Cai sp. nov. In this paper, the genus Sclomina is systematically revised, and the morphological characteristics of the five species are compared, described, and photographed in detail. We elucidate the evolutionary history of Sclomina based on results of estimated divergence time. The body shape and coloration (green in nymph and brown in adult) of Sclomina match their environment and mimic the Rubus plants on which they live. The symbiotic relationship between Sclomina and spinous Rubus plants is presented and discussed.