Effect of acclimated temperature on thermal tolerance, immune response and expression of HSP genes in Labeo rohita, Catla catla and their intergeneric hybrids

The ability of a species and population to respond to a decrease or an increase in temperature depends on their adaptive potential. Here, the critical thermal tolerance (CTmax and CTmin) of four populations: Labeo rohita, Cana cada, and their reciprocal hybrids L. rohita female x C. catla male (RC) and C. catla female x L. rohita male (CR) being acclimatized at four acclimation temperatures (22, 26, 30 and 34 degrees C) were determined. All populations indicated substantial variations (P < 0.05) in CTmax and CTmin values. L. rohita displayed, comparatively the highest CTmax with largest total and intrinsic polygon zones as well as the upper and lower acquired thermal tolerance zones followed by RC and CR hybrids, while C. catla showed significantly the highest CTmin value and the smallest intrinsic and acquired thermal tolerance zones. Both hybrids illustrated low parent hetemsis (<= 11%). Additionally, the highest expression of Hsp70 and Hsp90 (heat shock proteins) genes, serum lysozyme level, respiratory burst activity and lowest lipid peroxidation level under lower and higher temperature shock further illustrated strong physiological mechanism of L. rohita in contrast to C. cada, to deal with acute temperature, while hybrids, especially F1 RC hybrid appeared as a good option to replace C. catla in relatively higher and lower temperature areas.