Shrimp survival is affected by short-term stress, which produces symptoms similar to prostaglandin secretion. A short air-exposure (around 15-min) reduces the osmoregulatory capacity of shrimp, produces heart rate changes, decreased hemolymph pH. After air exposure and, when shrimp are submerged back into the water, there are increased oxidative damage and reduced survival. ). A higher 20:4n-6/20:5n-3 could promote the synthesis of prostaglandins (PG) by way of cyclooxygenase (COX) enzymes and PG regulate ion and water transport and the immune response in invertebrates. The synthesis of PG by COX can be inhibited on vertebrates using non-steroidal anti-inflammatory drugs (NSAID) such as acetylsalicylic acid (ASA). Here, we exposed shrimp to acute desiccation stress to evaluate if the response is regulated by PG and can be mitigated using ASA in the feed.
Pacific whiteleg shrimp Litopenaeus vannamei juveniles (1.5 ± 0.02 g) were obtained from a commercial hatchery (Acuacultura MAHR, S.A de C.V., La Paz, B.C.S.) and grown at the Nutrition Laboratory of CIBNOR (La Paz, B.C.S., Mexico) in six 600-L circular fiberglass tanks. Temperature, salinity, and dissolved oxygen were recorded once daily (27.0 ± 0.7°C, 36.0 ± 0.6 PSU and 5.0 ± 0.3 mg L‾1, respectively), Shrimp were fed to apparent satiation twice a day, using a grow-out diet containing 37 g kg-1 protein and 9 g kg-1 lipids prepared as described in Civera & Guillaume (1989). A control diet containing 93% of powdered grow-out feed, 5% squid meal as attractant, and 2% alginic acid as binder was fabricated, and ASA diet containing 91.8% powdered grow-out feed, 1.2% acetylsalicylic acid (ASA) as COX inhibitor, 5% squid meal, and 2% alginic acid. 19 juvenile shrimp (11.8 g) were distributed in six 600-L fiberglass tanks at a density of 15 shrimp per tank, fasted for the night, then fed the control diet and the ASA diet (0.15 g of feed g-1 shrimp) for one hour.. Half the shrimp from each tank were caught with a net, Non-stressed (NS), and frozen using liquid nitrogen. Stressed shrimp (S) were transferred to a 20-L container without water and left exposed to air for 15 min, then returned to tanks with seawater and aeration for 30 min to recovery, then they were caught and frozen with liquid nitrogen. Lipid hydroperoxides (LOOH), PG, lipids and biochemical analisis in gills were done.
During the stress, an 89% survival was found for the stressed controls, while shrimp fed ASA had 100% survival. The shrimp from the stressed group fed the ASA feed had a 73% of whitish abdomen, and of the stressed group fed the control diet had a 53% of whitish abdomen. The PG levels in gills significantly increased as a result of stress in the shrimp fed the control diet (25.8 pg mg-1), with lower levels in the stressed shrimp fed ASA (16.6 ± 4.5 pg mg-1) and non-stressed shrimp fed the control diet (11.2), and lowest in the non-stressed shrimp fed ASA (9.6 pg mg-1). The concentration of hydroperoxides (LOOH) in gills were not significantly different among treatments.