A common need in experiments evaluating biological processes in mosquitoes is the complete immobilization of the insect.  The most common method used to immobilize mosquitoes is cold-induced anesthesia.  In Drosophila melanogaster experiments, fruit flies are often anesthetized by exposure to vapors from a chemical solution called FlyNap, which contains the active ingredient triethylamine.  The purpose of this study was to determine whether in mosquito experiments, FlyNap-based anesthesia is a viable alternative to cold-induced anesthesia.  Using the malaria mosquito, Anopheles gambiae, we found that:

1. 1.FlyNap increases the mosquito heart rate.
   

2. 2.FlyNap alters the proportional directionality of heart contractions.
   

3. 3.FlyNap eliminates the cardioacceleratory effect of the neurohormone crustacean cardioactive peptide (CCAP).
   

4. 4.FlyNap reduces a mosquito’s ability to combat a bacterial infection.
   

Article Citation:

Chen, W., and J.F. Hillyer. 2013. FlyNap (triethylamine) increases the heart rate of mosquitoes and eliminates the cardioacceleratory effect of the neuropeptide CCAP.  PLoS ONE. 8(7):e70414.

doi:10.1371/journal.pone.0070414

(Download Free from the PLOS ONE Website)

Graphical Abstract:

Article Abstract:

FlyNap (triethylamine) is commonly used to anesthetize Drosophila melanogaster fruit flies.  The purpose of this study was to determine whether triethylamine is a suitable anesthetic agent for research into circulatory physiology and immune competence in the mosquito, Anopheles gambiae (Diptera: Culicidae).  Recovery experiments showed that mosquitoes awaken from traditional cold anesthesia in less than 7 minutes, but that recovery from FlyNap anesthesia does not begin for several hours.  Relative to cold anesthesia, moderate exposures to FlyNap induce an increase in the heart rate, a decrease in the percentage of the time the heart contracts in the anterograde direction, and a decrease in the frequency of heartbeat directional reversals.  Experiments employing various combinations of cold and FlyNap anesthesia then showed that cold exposure does not affect basal heart physiology, and that the differences seen between the cold and the FlyNap groups are due to a FlyNap-induced alteration of heart physiology.  Furthermore, exposure to FlyNap eliminated the cardioacceleratory effect of crustacean cardioactive peptide (CCAP), and reduced a mosquito’s ability to survive a bacterial infection.  Together, these data show that FlyNap is not a suitable substitute to cold anesthesia in experiments assessing mosquito heart function or immune competence.  Moreover, these data also illustrate the intricate biology of the insect heart.  Specifically, they confirm that the neurohormone CCAP modulates heart rhythms and that it serves as an anterograde pacemaker.