In addition, in response to hypoxia-induced diapause, most cells become arrested in the G1/G0 phase of the cell cycle which may favour genome integrity for the recovery phase. Delayed hatching is observed in both fish and amphibians and is typically associated with the deposition of eggs in an aerial environment. In contrast to diapause, delayed hatching seems to result in a reduced, but not arrested rate of metabolism and development. Comparison of hatching across teleostean taxa indicates great variability in the stage at hatching and in the duration of incubation, and therefore the plasticity for hatching time is likely linked to the embryo��s ability to sense environmental cues. An extensively studied fish model of delayed hatching is the common mummichog, Fundulus heteroclitus, a marine, non-migratory killifish typically inhabiting coastal marshes and inland systems. During the reproductive cycle of this species, gonad maturity and spawning readiness coincide with new and full moons, and spawning is thereby synchronized with the semi-lunar cycle of tides in the tide marsh habitat. Eggs are laid in multiple clutches at the high water mark during the high spring tides associated with new and full moons, and embryos develop in air and hatch when the next spring tide floods them. Northern populations of F. heteroclitus macrolepidus of North America may spawn throughout the tidal cycle on each high tide, and thus also in this case embryos will possibly be exposed to aerial incubations conditions for at least 14 days. It is thought that hypoxia caused by flooding with seawater is the major cue that initiates hatching, but the molecular Tubulin Acetylation Inducer mechanisms involved are not known. Incubation of F. heteroclitus embryos in aerial conditions most likely expose the embryos to higher levels of oxygen and higher temperature, which result in enhanced developmental rates, advanced or higher hatching, and larger hatchlings, with respect to embryos constantly submerged in water. Therefore, delayed hatching in F. heteroclitus is not associated with the depression of metabolism. However, aerially incubated embryos are likely to be also exposed to desiccation and thermal stress, and possibly osmotic stress due to water loss. Laboratorycontrolled experiments suggest that the low high content screening permeability of membranes of the embryonic compartments prevents significant water loss and allows prolonged survival of embryos in dehydrated conditions, regardless whether the desiccation conditions are stressful or not. In aerially incubated embryos at,100% relative humidity, Tingaud-Sequeira et al. found that expression of aquaporin-3a is down-regulated and removed from the basolateral membrane of the enveloping layer epithelium, which may account in part for the low permeability of the embryonic membranes during air exposure. These findings thus suggest that killifish embryos are able to transduce even moderate dehydration conditions into molecular responses within few hours of air exposure. However, in more severe desiccation conditions it has been hypothesized the role of additional mechanisms involving chaperone proteins such as heat shock proteins and compatible solutes such as free amino acids, which may help to stabilize vital cellular proteins. Although the plasticity of hatching is well described for fish and amphibians, the molecular mechanisms involved in the sensing and response of embryos to environmental cues are largely unknown. It is recognized, however, that adult populations of F. heteroclitus exhibit both physiological and adaptive responses to cope with the variable environments they inhabit, in which variations in gene expression have been shown to play a role in the evolutionary adaptation to diverse environments. Based on these and our previous studies, we hypothesized that killifish embryos may be able to rapidly transduce environmental.