Effect of fatty acids on survival, growth, morphology and stress tolerance of post-larvae of Farfantepenaeus paulensis
Some studies suggest that supplementation of highly polyunsaturated fatty acids of the n-3 family (n-3 AGAI) could increase survival, growth and stress tolerance in aquatic animals. In this work, we evaluated the effects of enriching Artemia franciscana (GSL, USA) with emulsions containing different fatty acid profiles on larviculture performance, morphological development and tolerance to salinity, temperature and total ammonia (N-AT) of post-larvae of the pink shrimp Farfantepenaeus paulensis (Pérez-Farfante, 1967). Larvae in the misis I stage were grown at an initial density of 60 individuals/L in 40L tanks until the age of post-larvae 10 (PL10). Groups of shrimp were fed exclusively with one of the following diets: (1) newly hatched Artemia nauplii;(2) nauplii enriched with emulsion based on saturated fatty acids (AGS) (emulsion ICES 0/-/C); and (3) nauplii enriched with emulsion (ICES 50/0.6/C) containing 50% highly unsaturated fatty acids (n-3 HUFA). Newly hatched nauplii were enriched for 24 hours with two doses of 0.3 g of emulsion/L added every 12 hours. The larvae were fed daily at 10:00 am and 10:00 pm. Upon reaching the age of PL10, survival, total length (CT; from the tip of the rostrum to the tip of the telson), development index and the morphology of the post-larvae (conformation of the central position of the telson, number of bristles) were estimated in the fifth abdominal somite, number of dorso-rostral spines and number of telson bristles). Tolerances to salinity,temperature and ammonia were evaluated by exposing PL10 to salinity 10 for 1h, 16-17 ° C for 1h and increasing levels of total ammonia (0, 15, 30, 45, 60 and 90 mg/L of N-AT) for 24 hours , respectively. Tolerances to salinity and temperature were expressed through the accumulated stress index (IEA; sum of the mortalities accumulated by 1h), while the tolerance to ammonia was estimated through the average lethal concentration for 50% of the population (LC50). All results were submitted to ANOVA and the Tukey's test (α = 0.05), with the exception of the LC50 values, which were compared graphically. The survival rates of PL1 and PL10 fed with Artemia meta-nauplii enriched with HUFA were significantly higher than in the other treatments. viii The total length of PL1 was not significantly different,but the PL10 fed with newly hatched nauplii were significantly higher. No significant differences were found in terms of rate of metamorphosis and tolerance to salinity and temperature. The conformation of the central position of the telson and the number of bristles in the fifth abdominal somite were significantly different, which did not occur for the number of dorso-rostral spines and that of the telson bristles. PL10 fed with Artemia meta-nauplii enriched with HUFA showed greater tolerance to ammonia. These results suggest that feeding F. paulensis larvae and post-larvae with Artemia meta-nauplii enriched with HUFA increases their survival and tolerance to total ammonia, which can be advantageous under adverse culture conditions.