Effects of high hydrostatic pressure on the pituitary-gonad axis in the European eel, Anguilla anguilla (L.).
European silver eels are thought to undergo sexual maturation during their oceanic reproductive migration from the European continent to their spawning area in the Sargasso Sea. Tracking data and various anatomical and physiological features suggest that silver eels migrate in deep sea, leading us to hypothesise that high hydrostatic pressure (HP) influences the induction of eel reproduction. We subjected female and male silver eels to 101ATA for 3 and 7 weeks, respectively, in a hyperbaric chamber equipped with a freshwater recirculation system. In comparison with control eels kept at 1 ATA, HP effects were tested against the messenger RNA levels of pituitary gonadotropins (LHbeta, FSHbeta) using quantitative real-time RT-PCR. The effects of HP on gonadal activity were estimated by measuring gonadosomatic index, oocyte diameter and plasma levels of vitellogenin (Vtg) and sex steroids (E(2), 11-KT). At the pituitary level, LHbeta expression tended to increase while FSHbeta expression decreased in both sex, leading to an increase in the LHbeta/FSHbeta ratio. This suggests a differential effect of HP on the expression of the two gonadotropins. In females submitted to HP, we observed a significant increase in oocyte diameter and plasma levels of 11-KT and E(2). A similar trend was observed for 11-KT plasma levels in males. In females, Vtg plasma levels also significantly increased, reflecting the stimulatory effect of sex steroids on hepatic vitellogenesis. Our results suggest that HP plays a specific and positive role in eel reproduction but additional environmental and internal factors are necessary to ensure complete sexual maturation.
Sébert
Marie-Emilie
ME
USM 0401, UMR 5178 CNRS/MNHN/UPMC Biologie des Organismes Marins et Ecosystèmes, Département des Milieux et Peuplements Aquatiques, Muséum National d'Histoire Naturelle, 75231 Paris Cedex 05, France.
Amérand
Aline
A
Vettier
Aurélie
A
Weltzien
Finn-Arne
FA
Pasqualini
Catherine
C
Sébert
Philippe
P
Dufour
Sylvie
S
D000220:Adaptation, Biological / Q000502:physiology*; D000811:Anguilla / Q000033:anatomy & histology / Q000097:blood / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001267:Atlantic Ocean; D004958:Estradiol / Q000097:blood; D005060:Europe; D005260:Female; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics / Q000378:metabolism; D006066:Gonads / Q000166:cytology / Q000502:physiology*; D006874:Hydrostatic Pressure; D007986:Luteinizing Hormone / Q000235:genetics / Q000378:metabolism; D008297:Male; D009929:Organ Size; D010902:Pituitary Gland / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D013739:Testosterone / Q000031:analogs & derivatives / Q000097:blood; D014819:Vitellogenins / Q000097:blood
D037201:Follicle Stimulating Hormone, beta Subunit; D012333:RNA, Messenger; D014819:Vitellogenins; D013739:Testosterone; D004958:Estradiol; D007986:Luteinizing Hormone; C003600:11-ketotestosterone