1. METABOLIC VARIATION OF JUVENILE PINK SHRIMP (Farfantepenaeus paulensis) DUE TO TEMPERATURE.
Edison Barbieria; Aline Maria Zigiotto de Medeirosa; Marcelo Barbosa Henriquesa*
aInstituto de Pesca - Secretaria de Agricultura e Abastecimento do Estado de São Paulo; Av. Bartolomeu de Gusmão, 192, Santos, SP, Brazil.
 *autor para correspondência:
INTRODUCTION
MATERIALS AND METHODS
Individuals of the species Farfantepenaeus paulensis, popularly known as “pink shrimp” are permanent representatives of estuarine fauna from Brazilian coast. We evaluated the influence of oxygen consumption and ammonia excretion on weight at different temperature ranges of juvenile individuals of F. paulensis collected in the coastal region of Cananéia, São Paulo State, Brazil (25°1'28''S; 47°55'56''W). We aim to contribute to the understanding of metabolic variations regarding prevailing factors that regulate the performance of the organism in intensive farming systems.
To study the routine metabolism variations and ammonia excretion of F. paulensis, we carried out 259 experiments in a respirometry system of sealed chambers, according to weight, at 15°C, 20°C and 25°C and salinity 35 g L-1. These values are within the range of temperature variation in the water column commonly found at the Cananéia Estuary. The shrimp were placed individually in round acrylic respirometry chambers and kept under water circulation for three hours, when the water supply was interrupted and the chambers were sealed. No significant differences were found for the amounts of oxygen consumption and ammonia excretion between males and females. We applied the regression analysis for each case and calculated the r correlation coefficients. We used the covariance analysis between the linear regressions and the Newman-Keuls test of multiple comparisons to identify the differences between the slopes and elevations of pairs of straight lines.
DISCUSSION
Temperature is one of the main environmental factors that regulates a number of metabolic reactions in ectotherm animals (DAMATO and BARBIERI 2011). Temperature effects on shrimp metabolic rate can be observed with the increase in a slopes as long as the straights are parallel, i.e., b values are not significantly different. Overall, slope increases linearly with temperature by moving the regression line in relation to the ordinates axis (ROCHA et al., 2001). In this study, b values were statistically similar to each other for regressions of oxygen consumption and ammonia excretion, allowing statistical analyses of slope as a means to estimate metabolic variations based on temperature and weight.
The data obtained in this study suggest that between 15-20°C is the temperature range that demands metabolism of pink shrimp. This temperature range needs to considered for culture efficiency in juveniles used in shrimp farming. This means that energy is concentrated for growth and other activities between 15-20°C. Temperature ranges apparently do not affect energy demand for metabolism from a biological standpoint (SCHMIDT-NIELSEN, 1997).
Individuals of the species studied are benthic organisms captured in the region from depths greater than 13 m to shallow waters of 2 m. They are certainly subjected to pronounced vertical temperature gradients that may favour adaptive strategies to optimize energy use at least within a certain variation range. Therefore, to accurately measure temperature effect on shrimp, the use of experimental ranges relatively narrow is important mainly when studying individuals of species subjected to unstable environments.
Fig. 1. The pink shrimp Farfantepenaeus paulensis.
Fig. 2. Shrimps in respirometers.
RESULTS
Oxygen consumption (R) and ammonia excretion (U) increased with increasing temperatures. The covariance analysis did not detect significant differences (p<0.05) between slopes (b) of linear regressions of oxygen consumption based on weight in any of the temperatures studied.
The same analysis, however, showed significant differences between the relationships (a). The Newman-Keuls test of multiple comparisons showed no significant differences (p<0.05) between a values in regressions for oxygen consumption at 15-20°C, showing that these values were similar at these temperatures. On the other hand, higher oxygen consumption at 25°C resulted in significant differences (p<0.05) between regression slopes at 15°C and 25°C, and 20°C and 25°C. Ammonia excretion increased with temperature. The covariance analysis did not show significant differences between b slopes. Comparisons of a slopes in the linear regressions show significant differences (p<0.05) for the three temperatures tested (Table 1).
CONCLUSION
Table 1. Regression between oxygen consumption and ammonia excretion for individuals of pink shrimp Farfantepenaeus paulensis and wet weight at three temperatures
The temperature range of 15-20°C is suggested as a range of thermal independence of F. paulensis metabolism, which is probably related to its physiological adaptation to environmental conditions. The results contribute to a better understanding of the ecological role of the species and its adaptation mechanisms to temperature.
Temperature
15°C
20°C
25°C O2
NH3 a
0.03
0.23
0.07
0.17
0.12
0.53 b
0.08
0.89
0.78
0.09
0.81 R
0.94
0.96
0.83
0.86 SD
0.06
0.33
0.49
Financial support
n=25; p<0.0001; SD – standard deviation