Significant improvement of shrimp growth performance by growth hormone-releasing peptide-6 immersion treatments

Growth hormone-releasing peptide-6 (GHRP-6) is one of the earliest developed synthetic peptidyl growth hormone secretagogue receptor agonists. These compounds mimic the effect of the endogenous ligand ghrelin. In vertebrates, ghrelin is a potent circulating orexigenic hormone with functional roles in controlling food intake, energy expenditure, adiposity, growth hormone secretion and immunity. Ghrelin has been studied mainly in vertebrates; thus, little is known about its role in invertebrates, including crustaceans. We first evaluated the effect of GHRP-6 injection over feed intake in shrimp and its effects on shrimp growth when the peptide was administrated by successive immersion baths. GHRP-6 increased feed intake, body weight and size, the number of rostral spines and gill branches, protein concentration and haemocyte number in treated shrimps. We also evaluated the peptide uptake and clearance in a pharmacokinetics, using [H-3]GHRP-6 administered to postlarvae. Given a limited exposure and efficient clearance of the peptide-associated radioactivity from larvae, our findings suggested that GHRP-6-treated Litopenaeus vannamei can be consumed safely by humans after aquaculture applications. These results propose that GHRP-6 could be an additional tool to study growth physiology in crustaceans and also a promising candidate for development into a new biotechnology product for improving shrimp growth and quality.