Fig. 6. Heart rate of zebrafish larvae between 2 d.p.f. and 12 d.p.f. under
normoxic conditions (PO2=20 kPa) and
progressive hypoxia down to anoxic conditions. Values are means ±
S.E.M. *Significant differences between normoxia and
hypoxic conditions (P<0.05). N values are given in
parentheses below each symbol.