Abstract
BackgroundHemolymph circulation in mosquitoes is primarily controlled by the contractile action of a dorsal vessel that runs underneath the dorsal midline and is subdivided into a thoracic aorta and an abdominal heart. Wave-like peristaltic contractions of the heart alternate in propelling hemolymph in anterograde and retrograde directions, where it empties into the hemocoel at the terminal ends of the insect. During our analyses of hemolymph propulsion in Anopheles gambiae, we observed periodic ventral abdominal contractions and hypothesized that they promote extracardiac hemolymph circulation in the abdominal hemocoel.Methodology/Principal FindingsWe devised methods to simultaneously analyze both heart and abdominal contractions, as well as to measure hemolymph flow in the abdominal hemocoel. Qualitative and quantitative analyses revealed that ventral abdominal contractions occur as series of bursts that propagate in the retrograde direction. Periods of ventral abdominal contraction begin only during periods of anterograde heart contraction and end immediately following a heartbeat directional reversal, suggesting that ventral abdominal contractions function to propel extracardiac hemolymph in the retrograde direction. To test this functional role, fluorescent microspheres were intrathoracically injected and their trajectory tracked throughout the hemocoel. Quantitative measurements of microsphere movement in extracardiac regions of the abdominal cavity showed that during periods of abdominal contractions hemolymph flows in dorsal and retrograde directions at a higher velocity and with greater acceleration than during periods of abdominal rest. Histochemical staining of the abdominal musculature then revealed that ventral abdominal contractions result from the contraction of intrasegmental lateral muscle fibers, intersegmental ventral muscle bands, and the ventral transverse muscles that form the ventral diaphragm.Conclusions/SignificanceThese data show that abdominal contractions potentiate extracardiac retrograde hemolymph propulsion in the abdominal hemocoel during periods of anterograde heart flow.
Highlights
In insects, the transport of nutrients, wastes and hormones between cells, as well as effective immune surveillance and killing of foreign invaders in the hemocoel, requires the continuous circulation of hemolymph throughout all regions of the insect [1,2]
All ventral abdominal contractions initiate at the thoraco-abdominal junction and propagate in a wave-like peristaltic manner toward the posterior of the insect, concluding in the last abdominal segment and resulting in ventrally directed abduction
The data on the percentage of time the heart contracts in the anterograde and retrograde directions were consistent with our earlier analyses of the mosquito heart [3], the average number of heartbeat reversals per minute is greater in this study, and the average individual heart contraction periods are shorter
Summary
The transport of nutrients, wastes and hormones between cells, as well as effective immune surveillance and killing of foreign invaders in the hemocoel (body cavity), requires the continuous circulation of hemolymph (blood) throughout all regions of the insect [1,2] This circulation of hemolymph is controlled by a series of myogenic pumps, with the primary pump being a dorsal vessel that is located underneath the longitudinal midline of the dorsal cuticle and extends the length of the insect (Figure 1A). Hemolymph circulation in mosquitoes is primarily controlled by the contractile action of a dorsal vessel that runs underneath the dorsal midline and is subdivided into a thoracic aorta and an abdominal heart. During our analyses of hemolymph propulsion in Anopheles gambiae, we observed periodic ventral abdominal contractions and hypothesized that they promote extracardiac hemolymph circulation in the abdominal hemocoel
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
