A rapid method for determining the physiological temperature parameters of giant freshwater prawn (Macrobrachium rosenbergii)
Description
Abstract Being ectothermic animals, prawns are highly sensitive to changes in environmental temperature. Uncomfortable temperatures can cause distress or even death in the animal and disrupt their activities. Current methods for detecting the physiological temperature ranges of prawns rely heavily on their behavior than on their intrinsic physiological characteristics. However, using external behaviors to identify distress in benthic crustaceans like prawns is challenging because they do not close their eyes, have expressionless faces, and often just lie dormant without extensive body movements. Recently, the concept of "oxygen- and capacity-limited thermal tolerance" was proposed for determining the living temperature range of animals, which is believed to depend on the oxygen supply capacity of each part of the body. Oxygen supply within organisms is heavily influenced by the circulatory and respiratory systems. This study examined respiratory and circulatory indicators to develop a set of methods for rapidly determining the physiological temperature range of prawns. This method can be used to determine the critical limit temperature, thermal tolerance range, pejus temperature, and optimal performance temperature without the need for large samples or long-term and extensive behavioral observations. This method assumes that the respiratory and circulatory systems respond in a coordinated manner when the temperature changes, which is indicated by the rate of change in both the scaphognathite beat and the heartbeat. On the basis of the ratio of these two rate changes at each temperature, we suggest several key physiological temperature ranges for Macrobrachium rosenbergii: (1) an upper critical temperature of 35°C and a lower critical temperature of 15°C, with a temperature tolerance of 15°C–35°C; (2) an upper pejus temperature of 33°C and a lower pejus temperature of 19°C; and (3) an optimal temperature range of 24°C–28°C, with the middle value of 26°C regarded as the optimal performance temperature.