Linking steroid hormone levels to sexual maturity index and energy reserves in Nereis diversicolor from clean and polluted estuaries

Abstract

The objective of this work was to compare seasonal variations of reproduction physiology of the ragworm Nereis diversicolor —a key species in estuarine ecosystems—originating from a clean (Authie) and multi-polluted (Seine) estuaries. A particular attention was carried out in female worms, on relationships between sexual maturity stages, energy reserves (glycogen and lipids) and steroid hormone levels (progesterone, 17β-estradiol, and testosterone). Sexual maturity index (SMI), energy reserves and steroid hormones are clearly influenced by season in worms from both sites. Depleted steroid hormone levels were depicted in specimens exhibiting high sexual maturity stage and energy reserves. Intersite analysis has revealed all over the sampling period:—a sexual precocity in worms from Seine,—glycogen concentrations generally higher in worms from Authie,—no clear tendency for lipids,—no differences in steroid hormone levels. Sexual precocity and lower glycogen levels in Seine could be explained by a specific strategy above all devoted to reproduction in these worms. Chemical stress could be a possible explanation of these observations.