Molecular pathways underlying Chaoborus air-sac structure and function
Aquatic larvae of the genus Chaoborus (Diptera: Chaoboridae) are the only truly pelagic insects in the world, able to precisely regulate their buoyancy to remain neutrally buoyant despite changes in partial pressure acting on them with changes in depth. Chaoborus larvae possess a pair of anterior and a pair of posterior air-filled sacs that change in volume, which results in changes to the overall density of the larvae; more volume of air allows the Chaoborus larvae to ascend as their density decreases, and less volume of air allows them to descend as their density increases. The air-sacs contain a thin layer of epithelial tissue beneath which lies an interior layer of alternating transverse bands of cuticle and resilin, an elastic protein which responds to changes in pH. Resilin stretches when in an alkaline environment, and contracts in an acidic environment. The molecular mechanisms involved in air-sac pH regulation was previously unknown. Using an RNAseq approach, I uncovered a suite of pathways found in the air-sac that are potentially involved in pH regulation. I propose a model in which VHA secretes H+ into the lumen, followed by Cl- via pHCl-2 and Clic to reduce the transmembrane potential and acidify resilin. To alkalinize resilin, I propose a model in which NHA1 and NHE2 work to exchange Na+ and K+ for H+, reducing the acidity of the lumen by removing H+, along with AE2, which exchanges luminal Cl- for HCO3-. These proposed models arise from a transcriptomic exploration into a previously unknown regulatory mechanism, uncovering potential pathways that can be verified in future studies.