en Aquaculture and Health management Aquaculture and Health management پژوهشي Original research papers <div style="text-align: justify;">Serum complement is valuable tool in determining the health status of fish. This study was conducted to examine <em>in vitro</em> activity of serum complement as an indicator of innate immunity in four sturgeon species, <em>Acipenser stellatus, A. baeri, A. nudiventris and Huso huso</em> (Chondrostei: Acipenseridae). The Effects of different temperatures, concentrations and volumes of serum on alternative complement pathway activity were evaluated using standard haemolytic assays in four sturgeon species (<em>A. stellatus, A. baeri, A. nudiventris and Huso huso</em>). Results indicated significant relation between measured hemolysis and concentration, volume and temperature (p<0.05). Maximal hemolytic activity was exhibited at 100% serum in four sturgeon species. (p<0.05). Exposure of different volumes of serum from sturgeon species to RBCs exhibited volume dependent hemolysis (p<0.05). Maximal hemolytic activity was resulted in 30 &mu;L of serum for all the sturgeon species. The highest hemolytic activity occurred at 4 &deg;C for all the sturgeon species, but the hemolytic activity decreased at 37 &deg;C. The results showed that the alternative complement pathway activity in sturgeon species serum may be affected by temperature, concentration and volume of serum that it caused an increase in non-specific immunity and the resistance to the outbreak of diseases.</div> <br> &nbsp;<br> &nbsp; Complement, Hemolysis, Immunity, Serum, Sturgeon 98 109 http://ijaah.ir/browse.php?a_code=A-10-211-1&slc_lang=en&sid=1 A Yektaseresht آزاده یکتا سرشت azadeh_neisi@shirazu.ac.ir 10031947532846002073 10031947532846002073 Yes 1Department of Pathobiology, School of Veterinary Medicine, Shiraz Universi دانشکده دامپزشکی شیراز، گروه ﭘاتوبیولوژی A Gholamhosseini امین غلامحسینی amingholamhosseini@gmail .com 10031947532846002074 10031947532846002074 No 2Department of Aquatic Animal Health and Diseases, School of Veterinary Medicine, Shiraz University, Shiraz, Iran. دانشکده دامپزشکی شیراز، گروه بهداشت وبیماریهای آبزیان A Janparvar علی جانپرور ali.ganparvar@yahoo.com 10031947532846002075 10031947532846002075 No 1Department of Pathobiology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran. دانشکده دامپزشکی شیراز، گروه ﭘاتوبیولوژی