De novo genome assembly, annotation, and characterization of chemosensory genes in Hippobosca camelina (camel ked).
Hippoboscid flies, or keds, are blood-feeding ectoparasites that infest birds, mammals, and occasionally humans. They belong to the Hippoboscoidea superfamily and are closely related to the sheep ked. Despite their role in transmitting pathogens such as Trypanosoma and Anaplasma species, their vector competence remains underexplored.
Genomic studies have advanced insect behavioral ecology and vector control strategies. However, the genome of Hippobosca camelina, a camel-feeding ked, is absent from databases, limiting insights into its chemosensory system and host detection mechanisms. Understanding these aspects is crucial for developing targeted, eco-friendly vector management tools.
While olfactory-based strategies have been effective in controlling related species like tsetse flies, the chemosensory mechanisms of keds remain poorly understood. This project aimed to bridge this knowledge gap by investigating the genetic and molecular basis of host detection in Hippobosca camelina, paving the way for improved control strategies.
Figure 1: Dorsal ventral view of Hippobosca camelina ked
Adapted from ICIPE insect of the month, photo by Daniel Masiga (Insect of the Month (January): Camel Fly, Hippobosca camelina | Icipe – International Centre of Insect Physiology and Ecology, 2024.)
Figure 2: Morphological characteristics of the head region of Hippobosca camelina.
(A) Head structure, (B) Antennal pit without antennal extension, (C) Scanned image of the antennal pit, (D) Arista. (Image was produced by Merid Getahum-International Centre of Insect Physiology and Ecology, Kenya).
In this study, it is postulated that Hippobosca camelina, an obligate organism with a narrow host range, is highly dependent on the chemosensory system for the detection of environmental signals such as high sensitivity to odours, heat, visual cues, humidity and other survival mechanisms such as predator evasion, mate location, and host finding. Therefore, this study aimed to assemble the genomes of Hippobosca camelina species and identify the putative chemosensory genes that support their superb chemical sensing ability.
The comprehensive list of softwares and packages used can be accessed here: Softwares and packages.
The genome size for Hippobosca camelina female is 135.6 Mb with 17.08% repeated regions, an N50 of 1.2 Mb, a total of 2,182 contigs, a GC content of 33.5%, and a Compleasm (BUSCO) completion rate of 95.38% with the diptera_odb10 lineage (S:95.83%, 3148, D:0.30%, 10, F:0.30%, 10, I:0.00%, 0, M:3.56%, 117, N:3285).
The Hippobosca camelina male had a genome size of 133.5 Mb with 15.38% being repeats, an N50 of 419.6 Kb, 2,318 contigs, GC content of 33.5%, and a Compleasm (BUSCO) completion rate of 94.70% with diptera_odb10 lineage (S:94.70%, 3111, D:0.49%, 16, F:0.85%, 28, I:0.00%, 0, M:3.96%, 130, N:3285).
A total of 14,240 putative genes for H. camelina male and 13,496 putative genes for H. camelina female annotated were identified as orthologous to genes in selected dipterans that included Drosophila melanogaster, Glossina morsitans morsitans, Glossina fuscipes, Glossina brevipalpis, and Anopheles gambiae.
Chemosensory genes recovered included 4 Chemosensory Specific Proteins (CSPs) genes, 18 Ionotropic Receptors (IRs), 7 Gustatory Receptors (GRs), 5 Odorant Receptors (ORs), 9 Odorant Binding Proteins (OBPs), and 1 Sensory Neuron Membrane Protein (SNMP).
Table 1: Comparison of Chemosensory Gene Numbers Across H. camelina, Melophagus ovinus, and Glossina morsitans.
The comparison includes gene counts for Chemosensory Specific Proteins (CSPs), Ionotropic Receptors (Irs), Gustatory Receptors (GRs), Odorant Receptors (ORs), Odorant Binding Proteins (OBPs), and Sensory Neuron Membrane Proteins (SNMPs), illustrating the differences in chemosensory gene numbers across these species and sexes.
| Chemosensory Gene Family | Hippobosca camelina | Melophagus ovinus | Glossina morsitans |
|---|---|---|---|
| Chemosensory Specific Proteins (CSPs) | 4 | 3 | 5 |
| Ionotropic Receptors (Irs) | 18 | 6 | 30 |
| Gustatory Receptors (GRs) | 7 | 11 | 14 |
| Odorant Receptors (ORs) | 5 | 2 | 46 |
| Odorant Binding Proteins (OBPs) | 9 | 3 | 32 |
| Sensory Neuron Membrane Proteins (SNMPs) | 1 | 0 | 2 |
Figure 3 Comparison of Chemosensory Gene Numbers Across H. camelina, Melophagus ovinus, and Glossina morsitans.
The comparison includes gene counts for Chemosensory Specific Proteins (CSPs), Ionotropic Receptors (Irs), Gustatory Receptors (GRs), Odorant Receptors (ORs), Odorant Binding Proteins (OBPs), and Sensory Neuron Membrane Proteins (SNMPs), illustrating the differences in chemosensory gene numbers across these species.
This study generated two genomes for Hippobosca camelina female and Hippobosca camelina male. Both of these are smaller in size compared to Melophugus ovinus (Zhang et al., 2023) and Glossina morsitans (Watanabe et al., 2014). The Hippobosca genomes have a lower repeat content compared to G. morsitans and M. ovinus, a phenomenon that may explain the reduced genome size.
A total of forty four chemosensory genes were annotated for Hippobosca camelina ked. The obligate parasitic lifestyle, limited movement, and narrow host specificity in Hippobosca camelina could be attributed to the reduced chemosensory system genes across the six known families of chemosensory genes as reported in this study.
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