Variation of prostaglandin E<inf>2</inf>concentrations in ovaries and its effects on ovarian maturation and oocyte proliferation in the giant fresh water prawn, Macrobrachium rosenbergii

Abstract

© 2015 Elsevier Inc. Prostaglandins (PGs) are important bioactive mediators for many physiological functions. In some decapod crustaceans, prostaglandin E2(PGE2) 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 PGE2and key enzymes for PGE2biosynthesis, as well as its effects on ovarian maturation have not yet been investigated. In this study we reported the presence of PGE2, cyclooxygenase1 (COX1) and prostaglandin E synthase (PGES) in the ovarian tissues of M. rosenbergii, using immunohistochemistry. Intense immunoreactivities of PGE2(PGE2-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 PGE2biosynthesis occurs in the ovary of this prawn. To ascertain this finding we used LC-MS/MS to quantitate PGE2concentrations during ovarian developmental cycle. The levels of PGE2were 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 PGE2stimulated 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.