Background: If European silver eels are prevented from reproductive migration, they remain in a prepubertal stage by dopaminergic inhibition of pituitary activity. Because this inhibition is likely a requirement for an extended female growth stage, we tested if it is sex-specific by subjecting both sexes to stimulation by GnRHa (Gonadotropin-Releasing Hormone agonist) - injection or 3-months swimming in seawater.
Results: In contrast to females, males showed a two- to three-fold higher LHbeta (luteinising hormone beta subunit) - expression, a three- to five-fold higher GSI (Gonadosomatic index) and induced spermatogenesis when compared with the untreated control group.
Conclusion: Dopaminergic inhibition is thus not effective in males and swimming results in natural maturation, probably via GnRH-release.