Effects of locomotor intensities on the locomotor behavior and energy metabolism of freshwater prawn Macrobrachium resenbergii

Locomotion is considered a fundamental property of most aquatic animals and is crucial for the survival of such animals. To explore the behavioral characteristics of locomotion and their relationships with muscle energy metabolism of Macrobrachium rosenbergii, the experiments of swimming and tail-flipping with four intensities (control, low, medium and high) were conducted. The behavior, energy sources and related metabolic enzyme activities of M. rosenbergii were determined after locomotion. The swimming intensities were obtained by setting different water velocities in a specific time period. The water velocities of control, low, medium and high intensity swimming were 0 (voluntary locomotion), 5 (200 min), 10 (200 min) and 15 cm/s (swimming until fatigue) respectively. The tail-flipping intensities were determined by setting different touch frequencies in a specific time period. The touch frequencies of control, low, medium and high intensity swimming were 0 (voluntary locomotion), 0.033 (5 min), 0.050 (5 min) and 0.067 Hz (tail-flipping until fatigue) respectively. Results showed that the maximum beat frequency (f_max) and maximum beat amplitude (A_max) of pleopods and uropods were significantly higher in each locomotor group than those in the control group. There were no significant differences in muscle protein contents among different locomotor groups. The contents of muscle glycogen were significantly decreased in each locomotor group compared with that in the control group. The lowest contents of triglyceride in pleopods muscles were observed in the low-intensity swimming group. The activities of lactate dehydrogenase (LDH) and lactate contents in pleopods muscles were significantly elevated in medium and high intensity swimming groups compared with those of control group. The activities of pyruvate dehydrogenase, malate dehydrogenase and lipase in pleopods muscles were significantly increased in low-intensity swimming group compared with those of control group. The LDH activities and lactate contents of abdominal muscles were significantly higher in each tail-flipping group than those of control group. Our findings indicate that the energies of locomotion are obtained by increasing the intensity of muscles energy metabolism in M. rosenbergii. The energy metabolism pathways of swimming vary according to swimming intensities. Tail-flipping is powered by anaerobic metabolism. These findings enhanced our understanding of physiology and behavior of locomotion in prawns, providing basic data for the healthy culture of M. rosenbergii.