Existence of an egg-laying hormone-like peptide in male reproductive system of the giant freshwater prawn, Macrobrachium rosenbergii

The giant freshwater prawn,Macrobrachium rosenbergii, is an important aquaculture species. A better under-standing of the molecular components of reproduction in this species would help to advance the prawn pro-duction. In the present study, we demonstrated the presence of an egg laying hormone (ELH)-like peptide in themale reproductive system. First, an antibody to the abalone (a)ELH was generated, and by Western blot it wasshown to specifically bound to a protein from the maleM. rosenbergiireproductive tissues with a similar size tomolluscan ELH. This aELH-like peptide was localized in spermatogonia in the testes of all three male morpho-types: blue claw, orange claw and small males. Moreover, the aELH-like peptide was detected in the epitheliumof the spermatic duct and its associated smooth muscle cell layers and on the outer surface of spermatozoa. Aswell, the aELH-like peptide was detected in the spermatophore located in the female thelycum at 4–6 h post-mating, indicating that it was transferred to the female during copulation. Taken together, we suggest that thisaELH-like peptide could be as a male inducing factor that helped to accelerate female spawning. Liquid chro-matography of crude extracts and immunoblot analysis suggested that the aELH-like peptide could be furtherpurified for ultimate characterization.