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| Aedes aegypti |
Following close on the news that creationism's malevolent... er... sorry... intelligent (sic) designer has designed liver flukes to be better at making us and our livestock sick, comes news of another brilliant piece if design to improve a mosquito's ability to give us serious infections with life-threatening parasites.
Researchers from the Department of Biological Sciences & Biomolecular Sciences Institute, Florida International University, Miami, FL, USA have shown how the antennae of female Aedes aegypti Mosquitoes can 'smell' characteristic signature chemicals in human body odour. Their findings were published open access in Current Biology yesterday.
This species of mosquito originated in Africa but is now found in tropical, subtropical and temperate regions throughout the world. It can carry yellow fever, dengue, chikungunya, Mayaro and is almost single-handedly responsible for the spread of the Zika virus which causes microcephaly in children if their mothers become infected during pregnancy.
The Florida International University team blocked a gene responsible for the ir8a co-receptor on the antennae of females and found that they were less able to detect their hosts to obtain a blood meal.
Highlights
- Ae. aegypti Ir8a mutant mosquitoes cannot sense lactic acid, a human sweat component
- Attraction to humans and human odor is reduced in Ir8a mutant mosquitoes
- Ae. aegypti IR8a pathway responds to human-odor cues during blood feeding
- The Ir8a mutant host-seeking defect cannot be rescued by other olfactory receptors
Summary
Mosquitoes use olfaction as a primary means of detecting their hosts. Previously, the functional ablation of a family of Aedes aegypti olfactory receptors, the odorant receptors (ORs), was not sufficient to reduce host seeking in the presence of carbon dioxide (CO2). This suggests the olfactory receptors that remain, such as the ionotropic receptors (IRs), could play a significant role in host detection. To test this, we disrupted the Ir8a co-receptor in Ae. aegypti using CRISPR/Cas9. We found that Ir8a mutant female mosquitoes are not attracted to lactic acid, a behaviorally active component of human sweat, and they lack odor-evoked responses to acidic volatiles. The loss of Ir8a reduces mosquito attraction to humans and their odor. We show that the CO2-detection pathway is necessary but not sufficient for IR8a to detect human odor. Our study reveals that the IR8a pathway is crucial for an anthropophilic vector mosquito to effectively seek hosts.
Raji, J. I., Melo, N., Castillo, J., Gonzalez, S., Saldana, V., Stensmyr, M., & DeGennaro, M. (2018).
Aedes Aegypti Mosquitoes Detect Acidic Volatiles in Human Odor Using the IR8a Pathway.
Current biology 2019 vol: 29 (8) pp: 1253-1262.e7 doi: org/10.2139/ssrn.3280246
Copyright: © 2019 The Author(s).
Published by Elsevier Ltd. Open Access
Reprinted under the terms of a Creative Commons Attribution – NonCommercial – NoDerivs License (CC BY-NC-ND 4.0)
The team found that blocking the co-receptor the ability to detect lactic acid in female Ae. aegypti was reduced by 50%. This offers the prospect of being able to develop more effective protection against Ae. aegypti, so eventually humans could become 'invisible' to Ae. aegypti.
The evolutionary explanation for this ability of a predator to find its prey is self-evident. Anything that improves that ability will give an advantage which will be passed on the the next generation in greater numbers than those without it.
For creationists, however, we have again the problem of explaining why an intelligent designer would go to these lengths to enable its designed delivery system to more effectively find humans and deliver their cargo of life-threatening parasites into their blood. Did this intelligent designer give Ae. aegypti this ability so babies could be born with microcephaly, or so people could die of yellow fever or dengue. The inescapable conclusion for an ID advocate is that this is exactly what it did, given that they believe this creator knows precisely what its designs will do and designs them to do precisely what they do. None of this could happen against the will of an intelligent designer who, even if it made a silly mistake, should be more than capable of undoing it.
To believe a designer made the Ae. aegypti mosquito and the parasites it infects humans with, and gave it a special ability to find humans by detecting a chemical in their sweat, is to believe this designer is malevolent to an astonishing degree of mendacity. Tweet
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