Growth, oxygen consumption, ammonia-N excretion, biochemical composition and energy content of Farfantepenaeus paulensis Perez-Farfante (Crustacea, Decapoda, Penaeidae) early postlarvae in different salinities

Physiological responses of early postlarval shrimp Farfantepeneus paulensis to different salinities were evaluated. Growth, net growth efficiency (K-2 ), oxygen consumption. ammonia-N excretion. protein, lipid, carbohydrate, a sh and energy content were determined in postlarval stages PL VI-VII and PL XIII-XV at 5 parts per thousand, 15 parts per thousand, 25 parts per thous and and 34 parts per thousand. PL VI-VII and PL XIII-XV correspond, in the wild, to the penetration of postlarvae into estuarine zones and the adoptio n of benthic habits, respectively. Postlarvae were gradually acclimated to the various salinity levels in the stage PL VI-VII and were maintained ther e until reaching the stage PL XIII-XV. Although development time was not af fected by salinity, growth was decreased at 34 parts per thousand. Oxygen c onsumption was less affected by salinity while ammonia-N excretion presente d a negative correlation with salinity. In both stages, protein content was lower at 34 parts per thousand. In PL VI-VII, lipid was decreased at 5 par ts per thousand. while no significant difference in lipid content was obser ved in PL XIII-XV. Carbohydrate and ash levels did not vary in function of salinity levels. Energy content was reduced in PL XIII-XV at 34 parts per t housand. Net growth efficiency (K-2) between PL VI-VII and PL XIII-XV prese nted higher values at 15 parts per thousand and 25 parts per thousand, and the lowest at 34 parts per thousand. Enhanced energy expenditure due to osm oregulation was not detected as denoted by oxygen consumption rates. Nitrog en metabolism seems to play a key role in maintaining body fluids concentra tion in relation to medium salinity. It is concluded that the high degree o f euryhalinity in these stages of F. paulensis may be an adaptation to onto genetic events such as migration to estuarine areas. For aquaculture purpos es, it is recommended to maintain these postlarval stages at salinities bet ween 15 parts per thousand and 25 parts per thousand rather than 34 parts p er thousand. (C) 2001 Elsevier Science B.V. All rights reserved.