Effect of Low Temperature on Globin Expression, Respiratory Metabolic Enzyme Activities, and Gill Structure of Litopenaeus vannamei.

Low temperature frequently influences growth, development, and even survival of aquatic animals. In the present study, physiological and molecular responses to low temperature in Litopenaeus vannamei were investigated. The cDNA sequences of two oxygen-carrying proteins, cytoglobin (Cygb) and neuroglobin (Ngb), were isolated. Protein structure analysis revealed that both proteins share a globin superfamily domain. Real-time PCR analysis indicated that Cygb and Ngb mRNA levels gradually increased during decrease in temperatures from 25 to 15°C and then decreased at 10°C in muscle, brain, stomach, and heart, except for a continuing increase in gills, whereas they showed a different expression trend in the hepatopancreas. Hemocyanin concentration gradually reduced as the temperature decreased. Moreover, the activities of respiratory metabolic enzymes including lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) were measured, and it was found that LDH activity gradually increased while SDH activity decreased after low-temperature treatment. Finally, damage to gill structure at low temperature was also observed, and this intensified with further decrease in temperature. Taken together, these results show that low temperature has an adverse influence in L. vannamei, which contributes to systematic understanding of the adaptation mechanisms of shrimp at low temperature.