The phase of elevated metabolic activity, during which oxygen consumption increases, that occurs at fertilization. An enhanced uptake of oxygen leads to the production of hydrogen peroxide (H2O2), superoxide anions and hydroxyl radicals. Capacitation, a necessary prerequisite event to successful fertilization, can be induced by reactive oxygen species in vitro; hydrogen peroxide is used as an extracellular oxidant to cross-link the protective surface envelopes. [ http://www.ncbi.nlm.nih.gov/pubmed/2537493 http://openisbn.com/search.php?q=0198506732&isbn=1/ http://www.ncbi.nlm.nih.gov/pubmed/9013127 ]