Physiological and behavioral responses of different modes of locomotion in the whiteleg shrimp Litopenaeus vannamei (Boone, 1931) (Caridea: Penaeidae)

Abstract

Shrimp locomotion includes walking, swimming, and tail-flipping, all essential for survival. Understanding the pathway and use of energy during different modes of locomotion is important in understanding the strategy and evolution of locomotion. We explored the mechanisms of energy supply during swimming and tail-flipping locomotion modes in the whiteleg shrimp Litopenaeus vannamei (Boone, 1931). We studied the metabolic pathways of glycogen and triglycerides and the regulation of glycolytic enzyme on glycolysis, and analyzed their relationship with the behavior modes of locomotion. Swimming includes sustained and prolonged modes, where the shrimp were forced to swim at a speed of 10 cm s -1 for 200 min (sustained), and at 20 cm s -1 until fatigue (prolonged). In tail-flipping locomotion, shrimp were forced to tail-flip by tapping the animal until fatigue. The results showed that the hydrolysis of glycogen in pleopod muscle increased with the rate of pleopod strokes due to increased energy demand during fast swimming. Similarly, glycogen breakdown in abdominal muscles was increased during tail-flipping. Glycogen and triglycerides were utilized in aerobic metabolism pathway as a result of the lower rate of pleopod strokes during sustained swimming. Prolonged and tail-flipping modes of locomotion were powered by anaerobic glycolysis because oxygen supply probably was not sufficient to meet the requirements of glycogen and triglyceride oxidation. Lactate accumulation due to increased glycolysis consequently resulted in locomotion fatigue. These findings highlight our understanding of physiology and behavior of locomotion in shrimps, essential during migration, foraging, and escape from predators.