Gametogenesis correlated with steroid levels during the gonadal cycle of the sea urchin Paracentrotus lividus (Echinodermata: Echinoidea) Alice Barbaglio a , Michela Sugni a , Cristiano Di Benedetto a , Francesco Bonasoro a , Sabine Schnell b , Ramon Lavado b , Cinta Porte b , Daniela M. Candia Carnevali a, ⁎ a Dipartimento di Biologia, Università degli Studi di Milano, Via Celoria 26, 20133, Milano, Italy b Environmental Chemistry Deparment IIQAB-CSIC. C/Jordi Girona, 18. 08034 Barcelona, Spain Received 11 October 2006; received in revised form 25 January 2007; accepted 25 January 2007 Available online 9 February 2007 Abstract The specific mechanism regulating reproduction in invertebrates is a field of topical interest which needs to be explored in detail considering also the intriguing possible comparison with vertebrates. In this paper levels of Testosterone (T) and Estradiol (E2) and their reciprocal ratios were determined in ovaries and testis of the echinoid model species Paracentrotus lividus during the year 2004 by taking into account a putative relationship between steroid levels and reproductive cycle. T levels appeared to significantly vary during male reproductive cycle, thus suggesting a possible role of this hormone in regulation of spermatogenesis as demonstrated for other echinoderms. E2 levels were lower in males with respect to females; consequently E2 involvement in oogenesis is hypothesized. In parallel with steroid levels evaluation, variations in P450- aromatase activity and its possible role on regulation of gametogenesis were also considered. Clear correlations between steroid levels and gonad index (GI), as well as between GI and reproductive cycle were not detected, suggesting that GI alone is not a reliable parameter in describing the reproductive status of the gonads. Altogether the results obtained so far confirm the presence of a relationship between steroid levels and reproductive cycle as suggested by previous results on different echinoderm species. © 2007 Elsevier Inc. All rights reserved. Keywords: Aromatase; Echinoids; Estradiol; Gonad index; Reproductive cycle; Testosterone 1. Introduction Reproductive physiology of echinoderms has been frequently investigated in terms of both their anatomical features and biochemical variations occurring in hormonal levels during gametogenesis. Although factors such as age, size, photoperiod, nutritional state and water temperature (Pearse and Cameron, 1991; Pearse and Bosch, 2002) were taken into account in order to define the roles of the different variables on echinoderm reproductive biology, convincing experimental evidence reported that typical hormones, particularly steroids, can have a specific role in echinoderm reproduction as well as in other physiological processes of these animals (Schoenmakers and Dieleman, 1981; Xu and Barker, 1990; Voogt et al., 1991; Hines et al., 1992; Watts et al., 1994; Wasson et al., 2000a). Different methods, namely bioassays, chromatography, radioimmunoas- say, gas chromatography–mass spectrometry (GC–MS) and NMR spectroscopy, revealed the presence of sex steroids in several echinoderm classes (Dieleman and Schoenmakers, 1979; Voogt et al., 1992; Watts et al., 1994). In particular cholesterol, progesterone, androstenedione, testosterone, 17β-estradiol and estrone were detected in starfishes, sea urchins and in a few species of other echinoderm classes (Schoenmakers and Diele- man, 1981; Voogt and Dieleman, 1984; Xu and Barker, 1990; Wasson et al., 2000a), most of the studies being referred to asteroids (Watts et al., 1994; Barbaglio et al., 2006; Georgiades et al., 2006; Lavado et al., 2006a,b). In the seastars Asterias rubens, Sclerasterias mollis and Asterias vulgaris, progesterone, estrone and testosterone levels appeared to vary according to the reproductive cycle with a sex-specific relationship (Voogt and Dieleman, 1984; Xu and Barker, 1990; Hines et al., 1992). Further laboratory tests demonstrated the ability of various echinoderms (mainly asteroids and echinoids and a few Comparative Biochemistry and Physiology, Part A 147 (2007) 466 – 474 www.elsevier.com/locate/cbpa ⁎ Corresponding author. Tel.: +39 02 503 14788; fax: +39 02 503 14781. E-mail address: daniela.candia@unimi.it (D.M. Candia Carnevali). 1095-6433/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.cbpa.2007.01.682