Higher acclimation temperature affects growth of rohu (Labeorohita) through suppression of GH and IGFs genes expression actuating stress response.

ABSTRACT

Water temperature alone can affect the growth, metabolic rates and physiological responses of aquatic organisms. Our earlier study reported that higher temperature affects cellular and hemato-biochemical responses in rohu, Labeo rohita. In this backdrop, the present study assessed the effect of higher acclimation temperature on the regulatory mechanisms of growth and stress responses of juvenile L. rohita acclimatized in three temperature conditions (30 °C, 33 °C, and 36 °C) for a period of 30 days. The relative expression of genes for growth hormone (GH), insulin-like growth factors (IGF-1 and IGF-2) and heat shock proteins (hsp70 and hsp90) were measured by real-time quantitative PCR. The results revealed that the highest acclimation temperature (36 °C) significantly decreased the weight gain (WG) and specific growth rate (SGR), and increased the feed conversion ratio (FCR) compared to 30 °C (control), while increased WG, SGR and lowered FCR were observed in fish reared at the intermediate temperature (33 °C) compared to 30 °C. Similarly, the GH gene expression in the pituitary was significantly decreased and increased at 36 °C and 33 °C, respectively as compared to 30 °C. A significantly lower expression of IGF-1 and IGF-2, and higher expression of hsp70 and hsp90 were observed in the liver of fish at 36 °C. The results of the present study indicate that although slightly elevated temperature promotes the growth of juvenile L. rohita, the higher acclimation temperature may induce stress response and impair growth performance by suppressing GH/IGF system.