Variation of prostaglandin E2 concentrations in ovaries and its effects on ovarian maturation and oocyte proliferation in the giant fresh water prawn, Macrobrachium rosenbergii.

Abstract Prostaglandins (PGs) are important bioactive mediators for many physiological functions. In some decapod crustaceans, prostaglandin E 2 (PGE 2 ) has been detected in reproductive organs, and may play a role in the control of ovarian maturation. However, in the freshwater prawn, Macrobrachium rosenbergii , the presences of PGE 2 and key enzymes for PGE 2 biosynthesis, as well as its effects on ovarian maturation have not yet been investigated. In this study we reported the presence of PGE 2 , cyclooxygenase1 (COX1) and prostaglandin E synthase (PGES) in the ovarian tissues of M. rosenbergii , using immunohistochemistry. Intense immunoreactivities of PGE 2 (PGE 2 - ir ), COX1 (Cox1- ir ) and PGES (PGES- ir ) were detected in previtellogenic oocytes (Oc1 and Oc2), while the immunoreactivities were absent in the late vitellogenic oocytes (Oc4). This finding supports the hypothesis that the PGE 2 biosynthesis occurs in the ovary of this prawn. To ascertain this finding we used LC–MS/MS to quantitate PGE 2 concentrations during ovarian developmental cycle. The levels of PGE 2 were significantly higher in the early ovarian stages (St I and II) than in the late stages (St III and IV). Moreover, we found that administration of PGE 2 stimulated the ovarian maturation in this species by shortening the length of the ovarian cycle, increasing ovarian-somatic index, oocyte proliferation, and vitellogenin (Vg) level in the hemolymph.