Ultrastructural evidences of the plastron organization and skin respiration in the soil inhabiting trombiculid mites (Acariformes: Trombiculidae)

This paper describes the main principles of organization and functioning of integument of the soil-inhabiting trombiculid mites (Trombiculidae) on the basis of electron microscopy and observation on mites in a laboratory culture. Dense cover of the long branched mechanoreceptive setae (neotrichia) functioning as a plastron retaining a significant air volume above the cuticle of these mites provides an effective respiration especially in unfavorable environmental conditions such as seasonal flooding, rains, etc. Additionally, specific organization of the integumental tissue favours conserving large masses of metabolic and sorption waters that reduces the rate of transpiration. Integumental folds provided with both the dense epicuticular ridges and the electron-clear intraepithelial cells filled with water are thought to function as real air gills, which selectively absorb and transport oxygen from the outside to the internal tissues and organs. Thus, plastron in the form of neotrichia and the integumental folds seem to function in the close physiological unity providing the effectiveness of respiration and water balance in the soil inhabiting trombicuilid mites.