Blood Properties of the Japanese Flounder (Paralichthys olivaceus) Suffocated to Death by Environmental Hypoxia

Abstract

The Japanese flounder Paralichthys olivaceus exposed to environmental hypoxia died at dissolved oxygen levels 1.13±0.25 mgO₂/l (20°C) within 12.5～21.5 h. Some blood properties of the flounder suffocated to death remarkably changed: significant rises in levels of lactate, plasma sodium ion, plasma potassium ion, plasma magnesium ion and blood total ammonia; significant falls in levels of plasma glucose and plasma calcium ion. However, the levels of hemoglobin (Hb), plasma total protein (Tpro) and plasma chloride ion did not shift significantly. Thus, the low lethal dissolved oxygen levels and no significant changes in Hb and Tpro suggest that the flounder, a generally inactive benthic teleost, probably has an intrinsic hypoxic tolerance which is attributed to a high blood O₂ affinity and a low oxygen demand at rest.