Can peptides be orally-delivered in crustaceans? The case study of the Crustacean Hyperglycaemic Hormone in Procambarus clarkii

The oral administration of substances in crustaceans is a growing field of research, and is considered the most ef- fective way to convey elements in their body instead injections or other invasive techniques. It presents huge po- tentialities, in fact the production of emulsions that preserves the substance to be conveyed until it reaches the target organ finds application in the development of new vaccines, in the convey of substances for aquaculture purposes and in the administration of stressors to contrast the spreading of invasive crustacean species. The red swamp crayfish (Procambarus clarkii, Girard 1852) is one of the most spread invasive species worldwide, but it is also considered among the most economically important freshwater crustacean species. For these rea- sons it is considered as a paradigmatic species. The chemical synthesis of the D-Crustacean Hyperglycemic Hormone isoform (D-Phe-CHH) from P. clarkii is here presented, with its species-specificity, verified through the injection of D-Phe-CHH in both the red swamp cray- fish and the threatened European species Austropotamobius italicus (Faxon, 1984). The D-Phe-CHH has been suc- cessfully oral-delivered in P. clarkii by using a water/oil/water microemulsion entrapped in a jellified matrix. After the administration of CHH, the glycaemia levels significantly increased in eyestalk-less animals at hour 6, and in intact crayfish at hour 5, from the ingestion. These encouraging findings pave the way for the use of the double emulsion method to oral administer different peptides to both handle physiological aspects of P. clarkii life cycle for aquaculture purposes and to create species- specific peptides-based mix to hamper the spreading of invasive crayfish populations. Statement of relevance: Through the injection of the de novo synthetized D-Phe-Crustacean Hyperglycaemic Hor- mone isoform in the haemolymphatic circulation of P. clarkii, we evaluated its action in triggering hyperglycaemia. The peptide has been then successfully orally delivered in P. clarkii by w/o/w microemulsion and its bioactivity has been demonstrated. The formulated emulsion to convey peptides in crustaceans represents a very promising technique to modulate growth and reproduction in aquaculture plans.