Extreme anoxia tolerance in embryos of the annual killifishAustrofundulus limnaeus: insights from a metabolomics analysis

Abstract

SUMMARY The annual killifish Austrofundulus limnaeus survives in ephemeral pond habitats by producing drought-tolerant diapausing embryos. These embryos probably experience oxygen deprivation as part of their normal developmental environment. We assessed the anoxia tolerance of A. limnaeus embryos across the duration of embryonic development. Embryos develop a substantial tolerance to anoxia during early development, which peaks during diapause II. This extreme tolerance of anoxia is retained during the first 4 days of post-diapause II development and is then lost. Metabolism during anoxia appears to be supported mainly by production of lactate, with alanine and succinate production contributing to a lesser degree. Anoxic embryos also accumulate large quantities of γ-aminobutyrate (GABA), a potential protector of neural function. It appears that the suite of characters associated with normal development and entry into diapause II in this species prepares the embryos for long-term survival in anoxia even while the embryos are exposed to aerobic conditions. This is the first report of such extreme anoxia tolerance in a vertebrate embryo, and introduces a new model for the study of anoxia tolerance in vertebrates.

Anoxia-Induced Suspended Animation in Caenorhabditis elegans

“…An example of a vertebrate that enters into an obligate diapause is the killifish embryo Austrofundulus limnaeus. A. limnaeus embryos in diapause II are remarkably tolerant to anoxia (Podrabsky et al, 2007). The mechanistic overlap between developmental arrests induced by anoxia in comparison to naturally occurring diapause remains to be determined.…”

“…Some organisms, including metazoans, exposed to stresses or naturally occurring signals can arrest processes such as development, cell division or heartbeat (Clegg, 2001;Mendelsohn et al, 2008;Padilla and Roth, 2001;Podrabsky et al, 2007;Renfree and Shaw, 2000;Riddle, 1988). Suspended animation is the arrest of observable biological processes induced by either a cue or stress in the environment, or a signal from within the animal.…”

Cell cycle regulation during development and dormancy in embryos of the annual killifishAustrofundulus limnaeus

“…These embryos can tolerate extremes in environmental salt concentration, 19 water availability 7 and oxygen content. 20 However, it is worth noting that early embryos of A. limnaeus are very hardy and can survive environmental stresses that would be lethal to most other species of vertebrates. In addition, the extreme tolerance of environmental stress exhibited by diapause II embryos is retained for several days of post-diapause II development.…”

“…20 In the context of metabolic dormancy, quiescence refers to a state of metabolic or developmental arrest in direct response to unfavorable environmental conditions. 11 Embryos that are faced with oxygen deprivation cease developing, 20 no longer .…”

“…20 In the context of metabolic dormancy, quiescence refers to a state of metabolic or developmental arrest in direct response to unfavorable environmental conditions. 11 Embryos that are faced with oxygen deprivation cease developing, 20 no longer . expression levels of p53 protein in diapause ii (Dii) and embryos 4 d post diapause ii (4 dpd) under normoxia, after long-term anoxia equal to one-half of the LT 50 for the developmental stage, and after 24 h of recovery from long-term anoxia.…”