Effect of thermal stress on Hsp70 gene expression and female reproductive performance of giant freshwater prawn, Macrobrachium rosenbergii

Using Hsp70 as a biomarker, thermal stress impinges on reproductive organs, ovary and hepatopancreas were being analyzed by determining the expression of Hsp70 mRNA inside the organs after the adult inter-molt females were subjected to thermal treatment at 35, 30 and 28 degrees C (Control). Results showed the expression of Hsp70 mRNA under thermal treatment of 35 degrees C after 2hr recovery in ovary were upregulated at 2, 4, 6, 12, 24hr and 30days compared to control whereas in hepatopancreas under similar treatment, the expression of Hsp70 mRNA were significantly higher than control at 6, 24hr and 30days. Frequency of reproductive molt at 35 degrees C showed the ovary of females were failed to develop and only entered common molt along three consecutive molt cycles. For 30 degrees C thermal treatment, the expression of Hsp70 mRNA was significantly higher than control after 2hr recovery but returned to normal afterwards until 30days' thermal treatment. Maternal heat shock for 2hr at 35 degrees C were found to give significantly lower frequency of reproductive molt and longer duration of ovarian development and incubation period whereas maternal heat shock for 2hr at 30 degrees C gave lower frequency of reproductive molt, slower development of embryo and lower hatching success compared to untreated control. This study suggests that short and long-term thermal stress at 30 and 35 degrees C were found to affect the induction of Hsp70 mRNA in reproductive organs of Macrobrachium rosenbergii and also influence their reproductive performance.