Research Article: The effects of razor clam (Solen vagina) acetone extract on immunity parameters and bacterial disease resistance in Litopenaeus vannamei

Bacterial infections are major limiting factors in shrimp culture that lead to great economic losses to the farmers. This study aimed to investigate the effects of Solen vagina acetone extract (AE) on some immunity parameters and bacterial infection by Vibrio harveyi in Litopenaeus vannamei.  5000 L. vannamei postlarvae were exposed to five concentrations (100, 150, 200, 250, and 300 mg/L) of S. vagina in triplicates for 3 weeks.  A positive control (exposed to the bacteria without any AE) and a negative control (without bacteria and AE) were also considered in this study. Each group contained 600 post larvae. The highest mortality was observed in the groups with concentrations of 100 and 150 mg/L AE and the lowest was observed at a concentration of 250 mg/L AE. None of the concentrations had a significant effect on the physical and chemical properties of water. According to the histopathology analyses, the exposed post larvae showed deformation symptoms in hepatopancreas cells. Based on the results, AE could reduce and prevent mortality caused by Vibrio harveyi. Also, the minimum inhibitory concentration of  AE for V. harveyi was 200 mg/L.