Endogenous opioid system and sharpsnout seabream (Diplodus Puntazzo) milt: detection of mu, delta and kappa opiod receptors on sperm cells

Sharpsnout seabream, (Diplodus puntazzo) is the third most farmed marine teleost species in Italy. Fish reproduction in aquaculture facilities is mainly obtained through environmental/pharmacological conditioning. These techniques may stress fish and decrease reproductive performances. Endogenous opioid peptides (EOPs) system is involved in stress response, and affects several physiological functions, both in central nervous system and in peripheral tissues. EOPs act through their specific cell membrane receptors (EOPr). The aim of the work is to evaluate the expression and localization of mu, delta and κappa opioid receptors in sharpsnout seabream milt by means of indirect immunofluorescence.Results show that mu opioid receptor is predominant localized on the tail, while delta and kappa seem to be located on the head. Opioid receptors detection on sharpsnout seabream milt let us suppose that the opioidergic system could modulate sperm motility, so that the use of opioid antagonists in fish farm could be useful to decrease stress effects on reproductive performances.