The Israeli Journal of Aquaculture - Bamidgeh 55(4), 2003
The 7th Annual Dan Popper Symposium


Yiftach Yashuvi¹, ³, Ulrike Klenke², Yonathan Zohar² and Yoav Gothilf ¹*

1 Department of Zoology, George S.Wise Faculty of Sciences, Tel Aviv University, Tel Aviv, Israel

2 Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland, USA

3 Madan, Ma'agan Michael Fish Breeding Center, Israel


Gonadotropin releasing hormone (GnRH) is a key hormone in the control of reproduction. Three kinds of GnRH neurons are distributed in the adult brain. GnRH-1 neurons are located in the preoptic area of the hypothalamus where they project axons into the pituitary gland and stimulate production and release of gonadotropin. GnRH-2 neurons, located in the midbrain, are believed to play a roll in reproductive behavior. GnRH-3 neurons are located in the terminal nerve where they presumably transduce olfactory signals into reproductive information. During embryonic development, GnRH-1 and -3 neurons originate in the nasal region and migrate along olfactory axons to the brain.

In this study we determined the onset of expression and the migration pattern of the GnRH neurons in hybrid striped bass larvae. Using whole mount in situ hybridization, GnRH-3 neurons were first localized in the nasal region two days after fertilization. Throughout the first 14 days of development, GnRH-3 mRNA signals expanded along the ventral telencephalon, reflecting the developmental migration of the GnRH-3. The GnRH-2 signal was detected in the midbrain two days after fertilization but no migration pattern was detected. GnRH-1 mRNA expression began 4-5 days after fertilization, as determined by PCR amplification analysis (GnRH-1 was undetectable using in situ hybridization.) Efforts are now being made to characterize its migration pattern using a recently cloned specific GnRH-1 cDNA.

Understanding the mechanisms that control the early migration and establishment of the GnRH neuronal systems may lead to the development of new approaches for inducing sterility in striped bass and other aquacultured fish, resulting in overall enhanced performance and profitability.