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In this study, we investigated (using bioassays and ELISA) the variation of cHH (crustacean hyperglycemic hormone) level in the eyestalks and hemolymph of Palaemon elegans (Rathke) (Decapoda, Caridea) following injection of serotonin (5-HT) and dopamine (DA) and correlated cHH profile with the variation in amount and time course of glycemia. 5-HT induced in P. elegans a rapid and massive release of cHH from the eyestalk into the hemolymph followed by hyperglycemia. On the contrary, DA did not significantly affect cHH release and hyperglycemia. In addition, we measured the level and variation of 5-HT in the eyestalk and hemolymph of P. elegans following copper contamination. The release of 5-HT from the eyestalk is very rapid and dose dependent. In the hemolymph, a peak of 5-HT occurs after 30 min, and again the circulating concentration of 5-HT is dose dependent on copper exposure. After 1 h, the level of 5-HT slowly decreases to basal level. The release of 5-HT from the eyestalk into the hemolymph after copper exposure precedes the release of cHH, confirming its role as a neurotransmitter acting on cHH neuroendocrine cells. The fact that copper induced a rapid and massive release of 5-HT from the eyestalk can explain its demonstrated role in inducing the release of cHH and the consequent hyperglycemia in intact but not eyestalkless animals.

This study investigates (by means of bioassays and ELISA using an antibody against recombinant cHH) the variation of cHH levels in the eyestalks and haemolymph of Palaemon elegans (Decapoda, Caridea) following exposure to various stresses (heavy metals and lipopolysaccharide), and correlates them with the variation in amount and time course of blood glucose. The dose-relationship between exposure to copper and quick release of cHH from the eyestalk into haemolymph was confirmed by variation of blood glucose with a dose-related hyperglycaemia, that peaked 2 h after immersion in contaminated seawater. Animals exposed to a sublethal concentration of mercury showed the same dose relation between toxicant, release of cHH from the eyestalk, increment of circulating hormone level and subsequent hyperglycaemia as observed for copper contamination. It is of note that although the highest lethal mercury concentration induced the release of cHH from the eyestalk into the haemolymph, it was not followed by a significant variation of blood glucose. Step doses of a bacterial contaminant [such as lipopolysaccharide (LPS) from E. coli injected into shrimps] confirmed the dose-relationship and convergent chain of events that bring about hyperglycaemia. These are the first data that relate the release of cHH from the eyestalk, the circulating hormone level and the consequent glycaemic response to stress. Moreover, they confirm the dose-related pathway that leads to variation of blood glucose as a quantitative biomarker of environmental quality, even at sublethal toxicant concentrations.