The influence of dietary arachidonic acid on the immune response and performance of Pacific whiteleg shrimp, Litopenaeus vannamei, at high stocking density

Stocking shrimp at high densities increases yield during culture, but growth is generally compromised and weakened immune response associated with poor water quality has also been reported. Therefore, we tested if supplying more arachidonic acid (ARA) in the diet, a precursor of eicosanoids such as prostaglandins E from the series II (PGE2) that enhance immune response can counteract the negative effect of stocking shrimp at high densities. The effect of physical crowding was separated from the effect of water quality, both a result of high density, by using tanks divided by a hard plastic net that allowed water flow between two density conditions. Crowding reduced weight gain by 8.3%, although the effect was more evident with deteriorated water quality from combined effects of high total ammonia and low dissolved oxygen levels (18.4%), but no effect on survival was found. A clear food imprinting of ARA levels in hemocytes was observed, but ARA did not clearly counteract the negative effects of high density on overall performance. However, ARA could minimize stress response of sampling and enhance some effectors of the immune system, such as clotting and respiratory burst. The increase in PGE2 metabolite in shrimp fed with the high-ARA diet was not consistent, and thus, the effects of ARA were not necessarily mediated by these eicosanoids

Effect of diets containing different levels of highly unsaturated fatty acids on physiological and immune responses in Pacific whiteleg shrimp <i>Litopenaeus vannamei</i> (Boone) exposed to handling stress

Juveniles fed a diet containing a low or a high level of highly unsaturated fatty acids (HUFA) for 38 days were exposed to handling stress. In a first experiment, stress was applied daily for 30 days, after which the physiological and immunological variables were measured, whereas in a second experiment, stress was applied once and samples were obtained 1 and 24 h after the stressor event. Shrimp that were stressed for 30 days showed significantly lower survival, final weight and feed consumption compared with unstressed shrimp. The concentration of the high-density lipoprotein beta-glucan-binding protein was significantly higher in shrimp fed the high-HUFA diet. The glucose concentration in the haemolymph was significantly higher in long-term stressed shrimp compared to controls. The lactate level in the haemolymph was significantly lower in shrimp fed the high-HUFA diet. Lactate and glucose in the haemolymph increased in the 1-h stressed shrimp, but returned to normal levels in 24-h stressed shrimp. A negative effect of repeated-handling stress applied for 30 days was mainly observed on biological performance, whereas the single-stressor event had a more pronounced effect on shrimp physiological and immune responses measured 1 and 24 h after the stressor. A beneficial role of enrichment with HUFA on tolerance to handling stress was observed on immune response capacity

Metabolic responses of adult lion's paw scallops Nodipecten subnodosus exposed to acute hyperthermia in relation to seasonal reproductive effort

WOS:000562870700002International audienceIn marine ectotherms, reproduction is an energetically expensive process that affects their thermal window tolerance. For most species, the impacts of hyperthermia during gametogenesis have still not been addressed. Our aim was to assess the metabolic response of adult Nodipecten subnodosus scallops to thermal challenges at early development (spring) and advanced gonad maturation (summer). Scallops collected in both seasons were exposed to acute hyperthermia (26 and 30 degrees C, 24 h), maintaining a group of scallops at acclimation temperature (22 degrees C) as a control condition. During the summer, relatively low activity of hexokinase (HK), as well as low levels of ATP and GTP were found in the adductor muscle, suggesting a shift in energy investment for reproduction, although arginine phosphate (ArgP) levels were higher in summer scallops. Hyperthermia (30 degrees C) induced an increased energy expenditure reflected by a transitory enhanced oxygen consumption (VO2) and relatively high activities of HK and arginine kinase (AK). Moreover, a slight decrease in adenylic energy charge (AEC) was partially compensated by a decrease in ArgP. An increase in nucleotide by-products inosine monophosphate (IMP) and hypoxanthine (HX) indicated a thermal stress at 30 degrees C. Some of the responses to acute hyperthermia were more pronounced at advanced maturation stages (summer scallops), indicating a possible lack of energy balance, with possible implications in animals challenged to global warming scenario