Research Article: Effect of sea cucumber, Holothuria parva,methanol extract on survival rate and immunity factors of white leg shrimp (Penaeus vannamei) exposed to Vibrio harveyi

This study aimed to investigate the effect of sea cucumber methanol extract on Vibrio harveyi and also to investigate the measurement of changes of factors in farmed shrimp, Penaeus vannamei. Holothuria parva with an average length of 15-10 cm were collected from tidal coasts of Dayyer city, Bushehr province. Different concentrations of H. parva extract (50, 100, and 150 µg/mL) were used to prepare the food of the experiment. Vibrio harveyi bacterial strain (PTCC: 1755) was obtained from the Collection Center of Industrial Microorganisms of Iran. Thousand shrimp with an average weight of 10±1 g were collected from culture ponds and distributed among 15 aquariums containing 100 liters of water with a salinity of 40 ppt. The mean comparison of survival rates showed that there was no significant difference among treatments on the first day (p>0.05). Also, there was significant difference among survival rates in other treatments with negative and positive control treatments (p<0.05). The results also showed that there was significant difference among the groups in PO (phenol oxidase), POD (peroxidase), THC (total haemocyte count), TPP (total plasma protein), and SOD (superoxide dismutase) with the amounts of negative and positive control treatments during the experimental days (p<0.05). The highest amounts of measured factors were 538.18±14.45 U min-1 mL-1 (Treatment 3) for PO on the fifth day, 7.19±0.3 nmol min-1 mL-1 (Treatment 2) for POD on the fifth day, 37.98±6.49×105 cell mL-1 (Treatment 3) for THC on the third day, 93.67±14.8 mg mL-1 (Treatment 3) for TPP on the third day, and 1663.21±37.07 activity U mL-1 (Treatment 3) for SOD on the third day. According to the results, survival was directly related to the concentration of methanolic extract. The highest increase in safety factors was observed in treatment 3, with concentration of 150 µg / mL methanolic extract of sea cucumber.