Factors inducing successful anhydrobiosis in the African chironomid Polypedilum vanderplanki:: Significance of the larval tubular nest

The African chironomid Polypedilum vanderplanki exhibits anhydrobiosis, i.e., the larvae can survive complete desiccation. Recovery rate and trehalose content were investigated in larvae desiccated slowly or at a rate more than 3 times faster. Upon slow desiccation (evaporation rate 0.22 ml day(-1)) larvae synthesized 38 mu g trehalose/individual before complete desiccation, and all of them recovered after rehydration, whereas larvae that were dehydrated quickly (evaporation rate 0.75 ml day(-1)) accumulated only 6.8 mu g trehalose/individual and none of them revived after rehydration. In the pools that are their natural habitat P. vanderplanki larvae make tubes by incorporating detritus or soil with their sticky saliva. This tubular structure is a physical barrier not only to protect the larva from natural enemies but also induces successful anhydrobiosis by reducing the dehydration rate. When larvae were dehydrated with 100 mu l distilled water (DW) in soil tubes, they accumulated 37 mu g trehalose/individual and more than half of them could revive after rehydration, whereas larvae without tubes accumulated lower level of trehalose and none recovered after rehydration.