Expression of guanylyl cyclase genes in medaka hybrids (Oryzias curvinotus x Oryzias latipes)

Effect of dietary astaxanthin on free radical scavenging capacity and nitrite stress tolerance of postlarvae shrimp, Pleoticus muelleri

The aim of this study was to investigate the effect of astaxanthin feed supplementation and environmental nitrite stress in postlarvae of Pleoticus muelleri (15 ± 0.004 mg initial weight) under culture conditions. Diets containing three levels of astaxanthin, 0 mg kg(-1) of diet (C0), 100 mg kg(-1) of diet (C(100)), and 300 mg kg(-1) of diet (C(300)), were used. Postlarvae fed with each diet were exposed to different concentrations of nitrite (NO(2)Na) (0-200 mg L(-1)). The 96 h median lethal concentration (LC50) values of nitrite N were 76.3, 89.7, and 157 mg L(-1) for shrimps fed to C0, C(100), and C(300). The scavenging properties were evaluated against the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical by electron resonance spectroscopy (EPR). For all feed treatments, the extracts exhibited strong DPPH scavenging activity; however, shrimp fed with C(100) and C(300) showed the greatest activity to quench DPPH (62 and 59%, respectively) with respect to C0 (43%). It can be concluded that astaxanthin acts as a protector of nitrite stress in P. muelleri.