en aquaculture aquaculture پژوهشي Orginal research papers <span style="font-size:11pt"><span style="line-height:120%"><span style="font-family:Calibri,sans-serif"><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">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 <i><span style="background:white"><span style="color:black">Solen vagina</span></span></i><span style="background:white"><span style="color:black"> acetone extract</span></span> (AE) on some immunity parameters and bacterial infection by <i>Vibrio harveyi </i>in <i>Litopenaeus vannamei</i>.&nbsp; 5000 <i>L. vannamei</i> postlarvae were exposed to five concentrations (100, 150, 200, 250, and 300 mg/L) of <i>S. vagina</i> in triplicates for 3 weeks.&nbsp; 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 <i>Vibrio harveyi</i>. Also, the minimum inhibitory concentration of&nbsp; AE for <i>V.</i> <i>harveyi</i> was 200 mg/L.</span></span></span></span></span></span> Acetone Extract, Solen vagina, Litopenaeus vannamei, Vibrio harveyi, Razor clam 1417 1429 http://jifro.ir/browse.php?a_code=A-10-1203-2&slc_lang=en&sid=1 Sh, Foroutan foroutan_iau@yahoo.com 100319475328460046597 100319475328460046597 No Islamic Azad university, Bandar Abbas Branch A.H. Bahri amirbahri52@yahoo.com 100319475328460046598 100319475328460046598 Yes Islamic Azad university, Bandar Abbas Branch B. Ghaednia Bghaednia@ifro.ir 100319475328460046599 100319475328460046599 No Iranian Fisheries Science Research Institute (IFSRI) , Agricultural Research Education and Extension Organization (AREEO), TIranian Fisheries Science Research Institute (IFSRI) , Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran F. Mohammadizadeh Fmohammadi13@gmail.com 100319475328460046600 100319475328460046600 No Islamic Azad university, Bandar Abbas Branch M. Mirbakhsh Maryam.mirbakhsh@gmail.com 100319475328460046601 100319475328460046601 No Iranian Fisheries Science Research Institute (IFSRI) , Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran