Cues of mosquito host finding and oviposition site selection

Afify, Ali

Cues of mosquito host finding and oviposition site selection

Files

Afify_289434.pdf(3.1 MB)

Date

2014

Authors

Afify, Ali

Publisher

Konstanz

Publication type

Dissertation

Abstract

The aim of this work was to study odor cues that affect mosquito host seeking and oviposition behavior. Due to the vastness (and sometimes contradictions) of mosquito oviposition cues available in literature, I started by reviewing these cues, their source in nature, and their role in mosquito oviposition. Then, I tested the oviposition response of Aedes aegypti towards the contradictory oviposition odor p-cresol and its isomer m-cresol in different situations.

p-cresol showed an oviposition deterrent effect at a broad range of concentrations (10-8-103 ppm) and stimulant effect only at 10-10 ppm while m-cresol was deterrent at 103 ppm only. Mixing the two compounds at 102 ppm yielded an oviposition deterrent effect. In addition, when both odors were presented in separate cups but together in the same cage, m-cresol was also perceived as deterrent suggesting an interaction between the two odors when presented in the same place.

Odors that influence mosquito host seeking could also affect oviposition. I confirmed the repellent effect of methyl N,N-dimethyl anthranilate and ethyl anthranilate on host seeking Aedes aegypti mosquitoes using a Y-tube olfactometer and showed that butyl anthranilate, which has been previously shown to be repellent, works only in still air situations. In addition, I showed that ethyl anthranilate and butyl anthranilate have an oviposition deterrent effect while methyl N,N-dimethyl anthranilate has no effect on Aedes aegypti oviposition.

To study odor coding in the mosquito antennal lobe, I presented a calcium imaging method and showed that it works to some degree in staining the antennal lobe. I also showed glomerular response in few mosquitoes towards significant odors, and the response to one of them (2-phenylethanol) was consistently in similar positions within the antennal lobe of different mosquitoes. Afterwards, I tested the host seeking and oviposition response of Aedes aegypti mosquitoes towards 2-phenylethanol, the odor which elicited the most stable response in calcium imaging experiments.

2-phenylethanol repelled host seeking mosquitoes at 10-3 and 10-2 and deterred oviposition at 10 and 100 ppm.
Finally, I tested the effect of prior experience on mosquito oviposition preference towards different concentrations of the oviposition pheromone n-heneicosane. I showed that raising Aedes aegypti larvae in 100 ppm n-heneicosane until eclosion resulted in a preference of the gravid females towards 100 ppm n-heneicosane over the innately preferred concentration 10 ppm.

Summary in another language

Ziel dieser Arbeit war es Düfte zu untersuchen, welche die Wirtssuche und das Eiablageverhalten von Moskitos beeinflussen. Aufgrund der Vielfalt und manchmal Widersprüchlichkeit der in der Literatur beschrieben Moskito-Eiablage-Signale habe ich diese Düfte, ihre natürlichen Quellen und ihre Rolle bei der Eiablage zu Beginn der Arbeit zusammengefasst. Anschließend habe ich das Eiablageverhalten von Aedes aegypti unter Einfluß des widersprüchlichen Eiablage-Duftes p-cresol und seinem Isomer m-cresol in verschiedenen Situationen untersucht. p-cresol zeigte über einen weiten Konzentrationsbereich (10-8-103 ppm) einen abschreckenden, bei 10-10 ppm einen stimulierenden Effekt auf die Eiablage. m-cresol war nur bei 103 ppm abschreckend. Eine Mischung aus beiden Stoffen bei 10-2 ppm hatte abschreckende Wirkung. Zusätzlich hatte m-cresol eine abschreckende Wirkung wenn es im selben Käfig wie p-cresol, jedoch in getrennten Behältern präsentiert wurde. Dies lässt auf eine Interaktion der beiden Substanzen schließen, wenn diese am selben Ort vorhanden sind.
Düfte, die die Wirtssuche von Moskitos beeinflußen, könnten auch einen Einfluß auf die Eiablage haben. Ich habe den abwehrenden Effekt von Methyl N,N-dimethyl anthranilat und Ethyl anthranilat auf die Wirtssuche von Aedes aegypti mittels eines Y-Olfaktometers bestätigt. Zudem konnte ich zeigen, dass Butyl anthranilat, welches bereits früher als Abwehrstoff beschrieben wurde, nur in windfreier Umgebung funktioniert. Außerdem habe ich gezeigt, dass sich Ethyl anthranilat und Butyl anthranilat negativ auf die Eiablage auswirken während Methyl N,N-dimethyl anthranilat keinen Einfluß auf dieses Verhalten bei Aedes aegypti hat.

Um die Duftkodierung im Antennallobus von Moskitos zu untersuchen, habe ich Kalzium-Imaging genutzt und gezeigt, dass die Anfärbung des Antennallobus zum Teil erfolgreich war. In einigen Moskitos konnte ich Antworten von Glomeruli auf wichtige Düfte messen. Die Antworten auf einen Duft (2-phenylethanol) waren an ähnlichen Stellen in den Antenalloben von verschiedenen Moskitos lokalisiert. Anschließend habe ich 2-phenylethanol, welches die stärksten Antworten im Kalzium-Imaging hervorrief, im Verhalten getestet. 2-phenylethanol hatte eine abschreckende Wirkung auf das Wirtssuche-Verhalten der Moskitos bei 10-3 und 10-2 sowie auf die Eiablage bei 10 und 100 ppm.
Abschließend habe ich den Einfluß von Erfahrung auf die Präferenz von verschiedenen Konzentrationen des Eiablage Pheromones n-heneicosane untersucht. Ich konnte zeigen, dass die Aufzucht von Aedes aegypti Larven in 100 ppm n-heneicosane bei trächtigen Weibchen darin resultierte, dass diese eine Konzentration von 100 ppm n-heneicosane präferierten anstatt, wie angeboren, 10 ppm.

Subject (DDC)

570 Biosciences, Biology

Keywords

Mosquitoes,Aedes aegypti,odor,cues,host finding,oviposition

Cite This

ISO 690

AFIFY, Ali, 2014. Cues of mosquito host finding and oviposition site selection [Dissertation]. Konstanz: University of Konstanz. Konstanz

BibTex

@phdthesis{Afify2014mosqu-28943,
  year={2014},
  publisher={Konstanz},
  title={Cues of mosquito host finding and oviposition site selection},
  author={Afify, Ali},
  address={Konstanz},
  school={Universität Konstanz}
}

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Examination date of dissertation

September 2, 2014