The mosquito circulatory system


Insects employ an open circulatory system for the transport of nutrients, wastes, and signaling molecules throughout the body.  The insect circulatory system also functions in thermoregulation, promoting ventilation through the tracheal system, and the circulation of humoral immune molecules and immune blood cells (hemocytes) that survey tissues for foreign entities.

Recently we completed a comprehensive characterization of the structural and functional mechanics of the mosquito heart, and showed that the primary organ driving hemolymph circulation in mosquitoes is a dorsal vessel that is subdivided into an abdominal heart and a thoracic aorta.  The heart is tethered to the midline of the abdominal tergum (dorsal cuticle) by alary muscles, and propels hemolymph at an average velocity of 8 mm/s by sequentially contracting muscle fibers oriented in a helical twist with respect to the lumen of the vessel.  The direction in which heart contractions propagate periodically switches direction, and hence, mosquitoes pump their hemolymph in both anterograde (toward the head) and retrograde (toward the posterior abdomen) directions. 

Using molecular and imaging techniques, we are currently investigating the hormonal control of heart contractions, the absolute speeds and direction of hemolymph flow in all areas of the insect, and the relative contribution of accessory pulsatile organs in potentiating extracardiac hemolymph propulsion.


Hemolymph propulsion in anopheline mosquitoes

Hemolymph propulsion in mosquitoes is driven by the contractile action of the heart and the accessory pulsatile organs.

The mosquito dorsal vessel is a tube-like structure that runs the length of the insect and is subdivided into an abdominal heart and a thoracic aorta.

Musculature of the dorsal abdomen, showing the heart and alary muscles.