抄録
Larvae of an African chironomid, Polypedilum vanderplanki live in temporal rock pools and they can stand complete desiccation in a cryptobiotic (ametabolic) state. The dehydrated larvae are able to revive within 1hr after rehydration. Here we studied the physicochemical mechanism of the cryptoiosis using FTIR microspectroscopy and DSC. When slowly dehydrated in the laboratory conditions over 48hrs, larvae synthesized a large amount of trehalose i.e. 36μg/individual and successfully went into cryptobiosis. In contrast the larvae quickly desiccated within several hrs produced as much as 3μg/individual of trehalose and never recovered after rehydration. Trehalose has a characteristic IR peak at 992cm^<-1>. We compared intensity distributions of this peak over the whole body followed by two dimensional contour maps for trehalose concentration between slowly and quickly dehydrated larvae. It was revealed that trehalose was almost uniformly distributed in the slow sample, but only little trehalose was detected in the quick sample. DSC measurements demonstrated that trehalose in the slow sample was vitrified with a glass transition temperature of ca. 50℃ (mid point). We obtained recovery rate of the rehydrated larvae after exposuring different temperatures for 5 min or 1h, which was interestingly well correlated with the glass transition behavior as mentioned above. We therefore concluded that vitrification of trehalose accumulated in the whole body was of importance in the successful induction of cryptobiosis in P. vanderplanki larvae.
