The structural analysis of secretion in the freshwater mite Limnesia maculata (O.F. Müller, 1776) (Acariformes, Limnesiidae) supports the idea of a new form of arthropod silk

Abstract

AbstractThe structural characteristics of silk secretion of the freshwater miteLimnesia maculata(O.F. Müller, 1776) (Acariformes, Limnesiidae) are described and analyzed for the first time based on light, atomic force and electron-microscopical approaches. The common dermal glands (14 pairs scattered over the body) produce silk mostly during the warm summer season. The process of silk secretion occupies from several hours to several days. Silk may be detected as barely recognized clouds of a fine whitish substance. An individual silk thread is an infinitely long uniform unbranched and non-stretchable tube, hollow or with a vesicular electron-dense residual content. In the silk bundle, threads may be freely interlaced, bent, curved or occasionally broken. The diameter of the tubes mostly lies within 0.9–1.5 µm. The width of the tube walls varies greatly from 60 to 300 nm. Chaotically interlaced fine fibrils build the tube walls. On the external surface of the tube wall, these fibrils are loosely organized and frequently rising vertically, whereas on the internal side they are packed more tightly sometimes showing a mesh. The walls may reveal a layered structure or, contrary, are quite thinner with through foramens. The revealed organization of silk in the freshwater mites is found to be the simplest among that of other arthropods. The proposed role of such silk is a capture of the potential prey in the summer season. Silk in water mites significantly widen the wholesome area for their life and gives them better chances in competition for potential resources.