TY - JOUR
T1 - GnRHa-mediated stimulation of the reproductive endocrine axis in captive Atlantic bluefin tuna, Thunnus thynnus
AU - Rosenfeld, H.
AU - Mylonas, C. C.
AU - Bridges, C. R.
AU - Heinisch, G.
AU - Corriero, A.
AU - Vassallo-Aguis, R.
AU - Medina, A.
AU - Belmonte, A.
AU - Garcia, A.
AU - De la Gándara, F.
AU - Fauvel, C.
AU - De Metrio, G.
AU - Meiri-Ashkenazi, I.
AU - Gordin, H.
AU - Zohar, Y.
N1 - Funding Information:
We would like to express our thanks to the personnel of S.A. Tuna Graso, for their assistance during the spawning induction experiments. We are particularly grateful to Luis Garcia Givert, the diver responsible for implanting the fish, whose expertise and dedication were instrumental for the success of this project. Thanks are also due to the staff of the Instituto Español de Oceanografía, Centro Oceanográfico de Murcia in Puerto de Mazarrón for their hospitality and assistance during the annual field experiments. We would like to express our gratitude to Dr. A.P. Scott (CEFAS Weymouth Laboratory, UK) for the analysis of free, conjugated and reduced steroids, and to Dr. S. Gorshkov (IOLR-NCM, Israel) for helpful assistance with the statistical analyses. This work was undertaken as part of the research program “Reproduction of the bluefin tuna in captivity – A feasibility study for the domestication of “Thunnus thynnus” (REPRODOTT), supported by a research grant from the European Community under the Quality of Life and Management of Living Resources program (contract Q5RS- 2002-01355).
PY - 2012/1/1
Y1 - 2012/1/1
N2 - A controlled-release implant loaded with GnRH agonist (GnRHa) was used to induce spawning in Atlantic bluefin tuna (Thunnus thynnus) during two consecutive reproductive seasons. The fish were implanted underwater and sampled between days 2 and 8 after treatment. At the time of GnRHa treatment, females were in full vitellogenesis and males in spermiation. There was a rapid burst of pituitary luteinizing hormone (LH) release at day 2 after treatment in GnRHa-treated fish, and circulating LH remained elevated up to day 8 after treatment. In contrast, control fish had significantly lower levels in the plasma, but higher LH content in the pituitary, as observed in many other cultured fishes that fail to undergo oocyte maturation, ovulation and spawning unless induced by an exogenous GnRHa. Plasma testosterone (T) and 17β-estradiol (E2) were elevated in response to the GnRHa treatment in females, while 11-ketotestosterone (11-KT) but not T was elevated in males. Even though oocyte maturation and ovulation did occur in GnRHa-induced fish, no significant elevations in 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) or 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S), in either the free, conjugated or 5β-reduced,3α-hydroxylated forms was observed in fish sampled within 6days after treatment. Interestingly, a significant peak in plasma free 17,20β-P levels occurred in both males and females at day 8 after treatment. Histological sections of the ovaries in these females contained oocytes at the migrating germinal vesicle stage, suggesting the role of this hormone as a maturation-inducing steroid in Atlantic bluefin tuna.In conclusion, the GnRHa implants activated effectively the reproductive endocrine axis in captive Atlantic bluefin tuna broodstocks, through stimulation of sustained elevations in plasma LH, which in turn evoked the synthesis and secretion of the relevant sex steroids leading to gamete maturation and release.
AB - A controlled-release implant loaded with GnRH agonist (GnRHa) was used to induce spawning in Atlantic bluefin tuna (Thunnus thynnus) during two consecutive reproductive seasons. The fish were implanted underwater and sampled between days 2 and 8 after treatment. At the time of GnRHa treatment, females were in full vitellogenesis and males in spermiation. There was a rapid burst of pituitary luteinizing hormone (LH) release at day 2 after treatment in GnRHa-treated fish, and circulating LH remained elevated up to day 8 after treatment. In contrast, control fish had significantly lower levels in the plasma, but higher LH content in the pituitary, as observed in many other cultured fishes that fail to undergo oocyte maturation, ovulation and spawning unless induced by an exogenous GnRHa. Plasma testosterone (T) and 17β-estradiol (E2) were elevated in response to the GnRHa treatment in females, while 11-ketotestosterone (11-KT) but not T was elevated in males. Even though oocyte maturation and ovulation did occur in GnRHa-induced fish, no significant elevations in 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) or 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S), in either the free, conjugated or 5β-reduced,3α-hydroxylated forms was observed in fish sampled within 6days after treatment. Interestingly, a significant peak in plasma free 17,20β-P levels occurred in both males and females at day 8 after treatment. Histological sections of the ovaries in these females contained oocytes at the migrating germinal vesicle stage, suggesting the role of this hormone as a maturation-inducing steroid in Atlantic bluefin tuna.In conclusion, the GnRHa implants activated effectively the reproductive endocrine axis in captive Atlantic bluefin tuna broodstocks, through stimulation of sustained elevations in plasma LH, which in turn evoked the synthesis and secretion of the relevant sex steroids leading to gamete maturation and release.
KW - Bluefin tuna
KW - Controlled-release implant
KW - GnRH
KW - LH
KW - Maturational inducing steroid
KW - Spawning
UR - http://www.scopus.com/inward/record.url?scp=84855198528&partnerID=8YFLogxK
U2 - 10.1016/j.ygcen.2011.09.013
DO - 10.1016/j.ygcen.2011.09.013
M3 - Article
AN - SCOPUS:84855198528
SN - 0016-6480
VL - 175
SP - 55
EP - 64
JO - General and Comparative Endocrinology
JF - General and Comparative Endocrinology
IS - 1
ER -