Functional Plasticity of Transferrins from Four Air-Breathing Channids (Genus Channa: Channidae) and its Relevance to their Survival

Channids are commercially important teleosts which can be cultured in shallow oxygen deficient waters due to accessory air-breathing. The information on metabolic plasticity of channids is inadequate; despite being fundamental to overall survival that determines their commercial output. To find out if transferrin (Tf) of genus Channa displays trends in functionality which correlate to their survival in shallow waters with low oxygen, we have compared iron-binding and pH dependent dispensation of bound iron in four channids (Channa punctatus, C. gachua and; C. striatus and C. marulius). Transferrin is central to iron metabolism as the main iron transporter and also intimately linked with oxygen-sensing. Our results show that their Tfs retain iron in exceptionally high amounts at acidic pH. Securing free iron at low pH should be imperative if respiratory acidosis occurs, since under low oxygen free iron (as Fe super(3+)) precipitates even at physiological pH. We suggest that retaining bound iron by Tfs at low pH values is a key factor in accomplishing iron homeostasis in channids with impact on fishery output.