Immunological and histopathological changes in Penaeus semisulcatus challenged with Vibrio harveyi

 Two-hundred and sixty five green tiger shrimp juveniles (Penaeus semisulcatus) with the average weight of ۷-۱۲g were collected from Helleh farms in Bushehr province and transported to Iran Shrimp Research Center of Bushehr in October, ۲۰۰۹. The juveniles were acclimated for two weeks. The experiment was designed in three treatments (named ۳, ۴ and ۵) and two controls (named ۱ and ۲) in triplicate with ۱۵ shrimp in each repetition prepared of glass aquarium. All the treatments and repetitions were exposed to Vibrio harveyi (NCBI: GU۹۷۴۳۴۲.۱). The concentrations of the treatments were ۱۰۸,۱۰۶ and ۱۰۴ CFU ml-۱ in individual containers dedicated for each mentioned treatment (۳, ۴ and ۵, respectively). The controls prepared with no any bacteria and fully filled with chlorinated and UV treated sea water were named ۱ and ۲ respectively. The hemolymph were withdrawn from abdominal segments of samples for measuring THC and TPC evaluation at designed hours (۲, ۶, ۱۲, ۲۴, ۴۸, ۹۶, ۱۴۴, ۱۹۲ and ۲۴۰). The shrimp samples were also fixed in Davidson fixative for histopathological studies. The results showed that the difference of THC value between controls and group ۳ during ۱۲ till ۹۶ hours of experiment was significant (P< ۰.۰۵). The differences between groups ۴ and control of THC value during ۲۴ to ۱۴۴ hours of experiment were also significant (P< ۰.۰۵). There was no significant difference (P> ۰.۰۵) between group ۵ and control groups of THC. The data showed that differences of TPC value between control groups during ۲۴ to ۹۶ hours were significant (P< ۰.۰۵), whereas the differences between controls with groups ۴ and ۵ during ۴۸ to ۱۴۴ hours and ۱۹۲ hours, were significant (P< ۰.۰۵) respectively. TPC and THC were observed with an increase in the concentration of bacteria and passing the time as inverse bell shape procedure. In histopathology, gills showed melanization and color changed to brown and black. The hepatopancreas cells revealed necrosis and vacuolization of B, E, R and F cells. The bolitas ball and bacterial colonization was observed in the intestine. Our results showed that Vibrio harveyi with ۱۰۸ and ۱۰۶ cell/ml decreased immunity factors such as THC and TPC. The histopathological changes increased with increasing the concentration of bacterial level. This finding can be used for assessing the health of shrimp culture and prevention of vibriosis.

Keywords:

Vibrio harveyi , Penaeus semisulcatus , Total hemocyte count , Total protein concentration , Histopathology