Seasonal fluctuations in pituitary levels of the three forms of gonadotropin-releasing hormone in striped bass, Morone saxatilis (Teleostei), during juvenile and pubertal development.
In most vertebrates, the development of a mature gonadotropin-releasing hormone (GnRH) secretory system is pivotal for the onset of puberty. The role of the three native GnRH forms, seabream (sb) GnRH, chicken (c) GnRH-II and salmon GnRH, in striped bass puberty remains elusive. This study examined the changes in pituitary GnRH levels throughout juvenile and pubertal development, a period encompassing 3 to 4 years. The levels of the two most abundant forms in the pituitary, sbGnRH and cGnRH-II (10:1), increased during the Fall and peaked prior to (cGnRH-II) or during (sbGnRH) the natural breeding season in March to May. In most cases, sbGnRH and cGnRH-II levels of maturing fish correlated to changes in oocyte diameter, gonadosomatic index and LH pituitary content. Interestingly, pituitaries of immature and maturing 2- and 3-year-old males and females contained similar amounts of all three GnRH forms. Additionally, pituitary sbGnRH and cGnRH-II levels in juvenile fish were relatively high and GnRH profiles showed a clear seasonality, similar to those of older, mature fish. These findings suggest a role for both sbGnRH and cGnRH-II in the regulation of gonadal development and indicate that, unlike some mammalian species, the timing of puberty in striped bass is not limited by a low activity of the GnRH system.
Holland
M C
MC
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, 701 East Pratt Street, Baltimore, Maryland 21202, USA.
Hassin
S
S
Zohar
Y
Y
D000375:Aging / Q000502:physiology; D000818:Animals; D001492:Bass / Q000254:growth & development*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D009865:Oocytes / Q000254:growth & development; D010902:Pituitary Gland / Q000254:growth & development* / Q000378:metabolism; D012621:Seasons; D012741:Sexual Maturation / Q000502:physiology*
D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-