Liet Chim

Effect of probiotic Pediococcus acidilactici on antioxidant defences and oxidative stress of Litopenaeus stylirostris under Vibrio nigripulchritudo challenge

Antioxidant defences and induced oxidative stress tissue damage of the blue shrimp Litopenaeus stylirostris, under challenge with Vibrio nigripulchritudo, were investigated for a 72-h period. For this purpose, L. stylirostris were first infected by immersion with pathogenic V. nigripulchritudo strain SFn1 and then antioxidant defences: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (Gpx), Total antioxidant status (TAS), glutathiones and induced tissue damage (MDA and carbonyl proteins) were determined in the digestive gland at 0, 12, 24, 48 and 72 h post-infection (h.p.i.). In the meantime, TAS was also measured in the blood. Infection level of the shrimps during the challenge was followed by determining V. nigripulchritudo prevalence and load in the haemolymph of the shrimps. Changes in all these parameters during the 72-h.p.i. period were recorded for control shrimps and shrimps previously fed for one month with probiotic Pediococcus acidilactici MA18/5M at 10(7) CFU g(-1) of feed. Our results showed that immersion with V. nigripulchritudo led to maximal infection level in the haemolymph at 24 h.p.i. preceding the mortality peak recorded at 48 h.p.i. Significant decreases in the antioxidant defences were detected from 24 h.p.i. and beyond that time infection leaded to increases in oxidative stress level and tissue damage. Compared to control group, shrimps fed the probiotic diet showed lower infection (20% instead of 45% at 24 h.p.i. in the control group) and mortality (25% instead of 41.7% in the control group) levels. Moreover, infected shrimp fed the probiotic compared to uninfected control shrimps exhibited very similar antioxidant status and oxidative stress level. Compared to the infected control group, shrimps fed the probiotic sustained higher antioxidant defences and lower oxidative stress level. This study shows that bacterial infection leads to oxidative stress in L. stylirostris and highlighted a beneficial effect of P. acidilactici, suggesting both a competitive exclusion effect leading to a reduction of the infection level and/or an enhancement of the antioxidant status of the shrimps.

Combined effect of temperature and salinity on osmoregulation of juvenile and subadult Penaeus stylirostris

In New Caledonia, the “syndrome 93,” which results in mass mortalities of farmed shrimp Penaeus stylirostris, occurs during the transitional and the cold seasons. The transitional season is characterized by an important fall in the average water temperature from 28 to 19 °C in 2 weeks. Besides this marked temperature fall, there are also nyctemeral temperature changes of up to 7 °C in 12 h. The cold season is characterized by an average water temperature of 19 °C with extreme lows of 14 °C. The objective of this study was to determine the effect of temperature and its variations on the osmoregulatory capacity of juvenile (7–10 g average weight) and subadult (25 g average weight) shrimps subjected to conditions of different salinity. A reduction in temperature level resulted in a decreased osmoregulatory capacity (OC) (defined as the difference between the osmolality of the haemolymph and that of sea water) at low salinity (hyper-CO) and at high salinity (hypo-CO), respectively, below and above the isoosmotic point (26.2 ppt). In subadult shrimps, the hyper-CO was affected when temperature dropped from 26 to 22 °C. The hypo-CO was modified only when temperature decreased down to 15 °C. Furthermore, the sensitiveness of osmoregulation to temperature changes was dependent on the developmental stage of the shrimp. Subadults were more sensitive than juvenile animals. The value of the isoosmotic point, which did not depend on the shrimp developmental stage, increased when temperature decreased to 17 or 15 °C. Our results provide an additional explanation of the “syndrome 93” and display the unfavourable influence of marked temperature drop on shrimp health. Our research could provide a possibility of seeking a nutritional and/or genetic solution to improve the capacity of the shrimps to maintain their homeostasis within a rearing medium with fluctuating temperatures.

Intensive culture of shrimp Penaeus vannamei in floating cages: zootechnical, economic and environmental aspects

Abstract In the framework of the France–Brazil cooperation in Oceanology, experiments have been carried out in the State of Bahia (Brazil) from 1992 on, in order to design a new technology for culture shrimps in floating cages in an estuarine zone. The zootechnical research has focused on the species Penaeus vannamei which has been tested in different rearing conditions (density in the cages) and seasons (wet and dry). The results may be compared with the most intensive and costly technologies which are practised in Asian countries. The average growth rate is about 0.8 g wk−1 and the average final biomass is 800 g m−2. The achieved results are all the more important as they are obtained with a simple technology which does not require energy for pumping and mechanical water aeration. Investigations on the impact of this kind of technology, carried out on a pilot site with estuarine conditions after three years of farming activity, showed no measurable effect on the sediment (in terms of organic matter) and in the water (in terms of oxygen). Economic analysis was recorded from the very beginning of the project, making it possible to design a computerised simulation tool in order to assess the feasibility of such an operation and to help in decision making for future research and development. Initial results indicate that ex-farm production costs for shrimps weighing 15 g would be around US

Rearing effect of biofloc on antioxidant and antimicrobial transcriptional response in Litopenaeus stylirostris shrimp facing an experimental sub-lethal hydrogen peroxide stress

4.7 per kg. The major competitive advantages of such a technique are the high yield, the quality of the product, the environmental friendliness and the positive social impact for a fishing community.

Probiotic P. acidilactici application in shrimp Litopenaeus stylirostris culture subject to vibriosis in New Caledonia

This study compares the antioxidant and antimicrobial transcriptional expression of blue shrimps reared according to two different systems, BioFloc Technology (BFT) and Clear sea Water (CW) and their differential responses when facing an experimental sublethal hydrogen peroxide stress. After 30 days of rearing, juvenile shrimps were exposed to H2O2 stress at a concentration of 30 ppm during 6 h. The oxidative stress caused by H2O2 was examined in the digestive glands of the shrimp, in which antioxidant enzyme (AOE) and antimicrobial peptide (AMP) gene expression were analysed by quantitative real-time PCR. Results showed that rearing conditions did not affect the expression of genes encoding AOEs or AMPs. However, H2O2 stress induced a differential response in expression between shrimps from the two rearing treatments (BFT and CW). Comparative analysis of the expression profiles indicates that catalase transcripts were significantly upregulated by H2O2 stress for BFT shrimps while no change was observed for CW shrimps. In contrast, H2O2 caused down-regulation of superoxide dismutase and glutathione transferase transcripts and of the three AMP transcripts studied (penaeidin 2 and 3, and crustin) for CW shrimps, while no effect was observed on BFT shrimp transcript levels. These results suggested that BFT shrimps maintained antioxidant and AMP responses after stress and therefore can effectively protect their cells against oxidative stress, while CW shrimp immune competence seems to decrease after stress.