Neuroendocrine and metabolic responses of Pacific whiteleg shrimp Litopenaeus vannamei exposed to acute handling stress

Abstract

The neuroendocrine mechanisms mediating stress in crustaceans are different and less understood than those of vertebrates, although indirect evidence suggests the participation of catecholamines (CA). However, few studies have analyzed their levels during stress response of crustaceans. We examined hemolymph and tissue levels of catecholamines and other biochemical indicators, in response to handling stress in whiteleg shrimp Litopenaeus vannamei. Shrimp were stressed by transfer, chasing, and confinement and the responses were analyzed at several intervals (10–240 min). Lactate levels in hemolymph increased from 10 to 30 min, glucose increased at 60 min, and both returned to baseline levels by 240 min. An increase in lactate levels before hyperglycemia suggests a possible activation of gluconeogenesis as a main clearance pathway for lactate. Epinephrine increased in hepatopancreas from 10 to 20 min, which indicates it could mediate lactate uptake, glucogenogenesis, and lipid catabolism in this organ. Norepinephrine levels in the eyestalk decreased by 92% between 20 and 30 min and a concomitant 10-fold increase in levels of dopamine was observed. This response suggested that the putative norepinephrine release in the X-organ sinus gland complex could mediate lactate effects in this organ (e.g. lactate positive feedback of crustacean hyperglycemic hormone release).