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Title: Studies on the time course of salinity and temperature adaptation in the commercial brown penaeus aztecus ives
Authors: Gulf Coast Research Laboratory (Ocean Springs, Miss.)
Venkataramiah, A.
Lakshmi, G. J.
Biesiot, Patricia.
Valleau, John D.
Gunter, Gordon, 1909-
Keywords: Aquatic ecosystems
Aquatic ecology
Marine ecosystems
Marine ecology
Temperature effects
Environmental effects
Salinity effects
Coastal engineering
Publisher: Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Contract report (U.S. Army Engineer Waterways Experiment Station) ; no. H-77-1.
Description: Contract Report
Abstract: The time course of salinity and temperature adaptation in brown shrimp Penaeus aztecus was determined by analyses of certain behavioral and physiological responses, the respiratory rates and osmotic and ionic regulation. The animals were transferred separately from a background salinity (S) 15‰ (control) and temperatures of 18°, 25° and 32°C to different test conditions for salinity adaptation. The test salinities were 2, 5, 10, 15, 25 and 36‰. and temperatures were 18°, 25° and 32°C. The duration of the tests was for one week (168 hours). The behavior of the experimental shrimp was influenced at 25°C which was their normal habitat temperature, primarily by salinity changes. At other temperatures the behavior was affected by the interaction of salinity and temperature. The blood osmotic and chloride ion regulation was hyperosmotic below and hyposmotic above the control salinity level. The rate of salinity adaptation was determined on the basis of steady-state levels in oxygen uptake and in blood osmotic or chloride concentration levels. At 25°C there was a positive interaction in the various phases of adaptation between the respiratory rates on the one hand and the osmotic and chloride ion gradients on the other hand in the respective salinities. This interaction was not consistent at other test temperatures. On the basis of osmotic and chloride ion steady-state levels, salinity adaptation was faster at 25°C than at either 18° or 32°C; also salinity adaptation occurred in a wider range of 2 to 36‰S within a week. The salinity range of adaptation decreased from 5 to 25‰ at 18°C and from 10 to 25‰S at 32°C. Within those salinity ranges the rate of mortality was usually low. Next to 25°C the salinity adaptation and survival rates were more favorable in 18°C than in 32°C. However, at 18° and 32°C the steady-state levels in the respiratory rates and in the blood osmotic (or chloride ion) concentrations appeared at different periods after the transfer was made. Consequently there was no synchrony between these responses at 18° or 32°C as opposed to 25°C test conditions. The respiratory rates at 18°C reached steady-state levels faster than the osmotic or chloride ion concentrations. On the contrary, at 32°C the steady-state levels appeared in the blood salt levels faster than in the respiratory rates. These discrepancies might have occurred partly due to the temperature-related differences in the behavioral pattern of shrimp. Normally the shrimp exhibited prolonged hyperactivity at 32°C and inactivity at 18°C which naturally influenced the respiratory rates both quantitatively and in relation to the time scale. In this report the implications of deriving conclusions on the state of salinity or temperature adaptation by taking individual physiological responses (i.e. respiratory rates) as an exclusive criterion are discussed. In brown shrimp, salinity and temperature requirements are shown to be size-dependent. The optima for subadult shrimp (95 mm mean length) seem to exist above 10‰S, preferably between 15 and 25‰S, and below 25°C. In contrast the juveniles (70 mm mean length) of our previous studies have shown preference to salinities lower than 17‰ and to temperatures slightly higher than 26°C. The possible existence of seasonal salinity and temperature optimal rhythms is discussed in relation to the life cycle of brown shrimp. Magnesium, calcium and potassium levels of the blood increased with salinity increases. Changes in test temperatures (18° or 32°C) affected the normal regulation pattern of these ions exhibited at 25°C. The physiological or behavioral responses were not significantly affected when minor changes occurred in these ionic ratios. Major changes, however, produced some physical abnormalities and high death rates. The effects became greater at temperatures higher than 18°C. Below 35 percent of the normal calcium levels the shrimp started dying; death rates increased with decreased calcium and increased temperature. Complete removal of magnesium from the test salinity was relatively less harmful than the reduced calcium levels. Reduced potassium killed even fewer shrimp, but produced a high incidence of abdominal (tail) cramps in shrimp. Low blood potassium levels and low temperature combinations seemed to cause the cramping in shrimp. NOTE: This file is very large. Allow your browser several minutes to download the file.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Contract Report

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