Insect Diapause

Our highly seasonal world restricts insect activity to brief portions of the year. This feature necessitates a sophisticated interpretation of seasonal changes and enactment of mechanisms for bringing development to a halt and then reinitiating it when the inimical season is past. The dormant state of diapause serves to bridge the unfavourable seasons, and its timing provides a powerful mechanism for synchronizing insect development. This book explores how seasonal signals are monitored and used by insects to enact specific molecular pathways that generate the diapause phenotype. The broad perspective offered here scales from the ecological to the molecular and thus provides a comprehensive view of this exciting and vibrant research field, offering insights on topics ranging from pest management, evolution, speciation, climate change and disease transmission, to human health, as well as analogies with other forms of invertebrate dormancy and mammalian hibernation.

Mammalian hibernation: a unique model for medical research

Hibernation is an adaptive behavior for some small animals to survive cold winter. Hibernating mammals usually down-regulate their body temperature from ~37°C to only a few degrees. During the evolution, mammalian hibernators have inherited unique strategies to survive extreme conditions that may lead to disease or death in humans and other non-hibernators. Hibernating mammals can not only tolerant deep hypothermia, hypoxia and anoxia, but also protect them against osteoporosis, muscle atrophy, heart arrhythmia and ischemia-reperfusion injury. Finding the molecular and regulatory mechanisms underlying these adaptations will provide novel ideas for treating related human diseases.

Generalized harmonic analysis reveals a frequency modulated timer regulates mammalian hibernation

Mammalian hibernators decrease basal metabolism and body temperature (Tb) to minimize energy expenditure in harsh seasons. During hibernation, Tb drops to low temperature (<10 °C) and remains constant for days, known as deep torpor. Spontaneous interbout arousals interrupt torpor bouts, when Tb recovers to euthermic state ~37 °C. Torpor-interbout arousal event repeats during hibernation. Little is known about mechanisms governing Tb fluctuation during hibernation. Here, we analyzed Tb fluctuation across Syrian hamsters′ hibernation cycle using generalized harmonic analysis and discovered a model with frequency modulation quantitatively reproducing Tb fluctuation. This analysis identified that an unexpectedly longer period of 120—430 days modulates period of several days, generating Tb fluctuation. We propose that concerted action of two endogenous periods governs torpor-interbout arousal cycles during hibernation.