Estivation is a state of dormancy, typically triggered by arid conditions when food/water availability is poor or absent and often occurs in hot weather. Many estivators live in desert or semi-arid environments. It is not uncommon for estivating species to spend many months of the year in dormancy, emerging only in brief rainy seasons to feed and reproduce. Estivators typically take steps to minimize water loss from their bodies while dormant using physical barriers (e.g. snails seal the opening of their shell, frogs and lungfish can secrete a cocoon made of shed skin or mucus), biochemical methods (increasing the osmotic pressure of body fluids), and storing large amounts of body water before entering dormancy (e.g. frogs maintain a huge reservoir in the bladder and can resorb water from there). The Storey Lab works on 3 main estivating model animals; Land snails, Spadefoot toads, and African clawed frogs.
New studies have moved in different directions. Studies of signal transduction are analyzing the protein kinases and phosphatases, second messengers and transcription factors that are responsible for initiating and coordinating metabolic arrest. Studies of gene expression are identifying genes that are up-regulated during entry into or arousal from arrested states, analyzing the patterns and influences on gene expression, and investigating the roles of the associated gene products. New work has identified multiple mechanisms that participate in the global suppression of gene transcription in hypometabolic states including histone modification, control of RNA polymerase II, and inhibition of mRNA translation via the actions of microRNA species. The research shows that these mechanisms form a common basis for the control of metabolic rate depression across phylogeny.
Estivating animals: African clawed frog, Couch’s spadefoot toad, Milk snails