The wings of insects are composed of membranes supported by interconnected veins. Within these veins are epithelial cells, nerves and tracheae, and their maintenance requires the flow of hemolymph. For this purpose, insects employ accessory pulsatile organs (auxiliary hearts) that circulate hemolymph throughout the wings. Here, we used correlative approaches to determine the functional mechanics of hemolymph circulation in the wings of the malaria mosquito Anopheles gambiae. Examination of sectioned tissues and intravital videos showed that the wing heart is located underneath the scutellum and is separate from the dorsal vessel. It is composed of a single pulsatile diaphragm (indicating that it is unpaired) that contracts at 3 Hz and circulates hemolymph throughout both wings. The wing heart contracts significantly faster than the dorsal vessel, and there is no correlation between the contractions of these two pulsatile organs. The wing heart functions by aspirating hemolymph out of the posterior wing veins, which forces hemolymph into the wings via anterior veins. By tracking the movement of fluorescent microspheres, we show that the flow diameter of the wing circulatory circuit is less than 1 µm, and we present a spatial map detailing the flow of hemolymph across all the wing veins, including the costa, sub-costa, ambient costa, radius, media, cubitus anterior, anal vein and crossveins. We also quantified the movement of hemolymph within the radius and within the ambient costa, and show that hemolymph velocity and maximum acceleration are higher when hemolymph is exiting the wing.
The authors declare no competing or financial interests.
J.F.H. conceived the study. R.T.V.C. and J.F.H. designed and performed the experiments, analyzed the data, and wrote the manuscript.
This research was funded by US National Science Foundation (NSF) grant IOS-1257936 to J.F.H., Vanderbilt University Littlejohn fellowships to J.F.H. and R.V.C., and an Arnold and Mabel Beckman Foundation scholarship to R.V.C. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of this manuscript.
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.148254.supplemental
- Received August 12, 2016.
- Accepted October 6, 2016.
- © 2016. Published by The Company of Biologists Ltd