Open Research Journal of Fisheries and Aquaculture Vol. 1, No. 1, July 2013, PP : 01-05 http://www.scitecpub.com/Journals.php Available online at Copyright © www.scitecpub.com, all rights reserved. 1 RESEARCH ARTICLE THE AYU: EFFECT OF ISRAELI AQUACULTURE ON GROWTH, GONAD DEVELOPMENT, AND GENE TRANSCRIPTION OF FSH,  LH AND GH Gad Degani 1, 2 *and Avshalom Hurvitz 1 , 1 MIGAL – Galilee Technological Center, Kiryat Shmona 11016, Israel; 2 School of Science and Technology, Tel-Hai Academic College. * Corresponding Author: Prof. Gad Degani, MIGAL – Galilee Technological Center, Kiryat Shmona 11016, Israel, Tel.: 972-4-6953544, Fax: 972-4-6944980, E-mail: gad@migal.co.il __________________________________________________________________________________________ SUMMARY The ayu (Plecoglossus altivelis) is a teleost with a one-year life cycle, and following reproduction, the fish usually die. In this study, we describe the ayu, which has been adapted to Israeli aquacultural conditions. The ayu ovaries were examined at vitellogenesis, their  FSH,  LH and growth hormone cDNAs cloned, and the expression of these genes in females at vitellogenesis, measured. Ayu ovaries are of the group-synchronic type and have two distinct batches of oocytes. A low gonad somatic index (GSI) percentage was noted in the small females, as opposed to a high variation in the medium and large females. cDNAs encoding the  subunits of gonadotropin hormones, FSH and LH, and the growth hormone (GH) from the pituitary glands of ayu, were cloned. The similarity between the  subunits of FSH and LH was only 32%, and the deduced amino acid sequences of both ayu LH cDNAs were very similar to their salmonid counterparts. The GH sequence showed an 81% and 75% similarity to the O. tshawyscha nucleotide and amino acid sequences, respectively. The expression study demonstrated that vitellogenic females expressed both  FSH and  LH, an expression pattern common to the teleost, with group-synchronic ovary development. Keywords: ayu, gonad development, gonadotropin transcription, Israeli aquaculture. __________________________________________________________________________________________ INTRODUCTION Gonadotropins (GtHs) are glycoproteins, consisting of two non-covalently bound subunits,  and . Today, the existence of two distinct GtHs, FSH and LH, in the pituitary gland of teleosts, is well accepted. It is believed that FSH regulates gametogenesis, since it promotes the production of 17 estradiol and the incorporation of vitellogenin into the oocytes (Sekine, Saito, Itoh, Kawauchi. & Itoh 1989; Rodriguez, Suzuki, Peter & Itoh 1993). LH, on the other hand, is known to be involved in oocyte maturation and ovulation (Prat, Sumpter & Tyler 1996). This hormone is probably responsible for the final maturation of oocytes (FOM), as it is more active than FSH in stimulating the release of the maturation-inducing factor produced by post-vitellogenic oocytes (Nagahama 1994). The  and  subunits of teleost FSH and LH are encoded by separate genes (Jackson, Goldberg, Ofir, Abraham & Degani 1999; Kajimura, Yoshiura, Suzuki & Aida 2001).