SALINITY, TEMPERATURE, AND SEASONALITY EFFECTS ON THE METABOLIC RATE OF THE BROWN SHRIMP FARFANTEPENAEUS AZTECUS (IVES, 1891) (DECAPODA, PENAEIDAE) FROM THE COASTAL GULF OF MEXICO

摘要

The routine metabolic rate [QO_2 in mg O_2 g~(_1) DW h~(_1)] was measured in juvenilesof the brown shrimp, Farfantepenaeus aztecus (Ives, 1891) at salinity and temperature ranges prevailing during the cold and warm seasons at the coastal lagoon of Tamiahua, Veracruz, Mexico. A semi-closed respirometer was employed, with eight 4-L experimental chambers, each containing two shrimp of similar size and sex. The shrimp were fasting and in the intermoult stage, and acclimated to the chambers for 12 h prior to determining oxygen consumption. Oxygen measurements were taken every two hours with apartial replacement of water and aeration of one hour between readings. In a 24 h cycle, 6 to 8 measurements were made. Relations between QO_2 and DW, for the different salinity and temperature conditions tested, were calculated and adjusted to the equation: QO_2 = alpha DW~(beta). Two -way ANOVA was applied to analyse the effect of salinity, temperature, time of day, and body weight onF. aztecus QO_2. Salinity had no significant (p > 0.05) effect upon the shrimp's routine metabolic rate at intervals of 26 to 34 psu and 22 to 36 psu, typical of the cold and warm seasons, respectively. However, seasonal temperature variation did significantly affect the shrimp's QO_2, thus suggesting the existence of a different "pattern of acclimatization" in the energy requirements of the individuals from both seasons. The results indicate that the population of F. aztecus from this area of the Gulfof Mexico may represent a "cline", the physiological response of the components of which differs from that of other brown shrimp populations distributed over a wide geographical range in the western tropical Atlantic.