title: Male silver eels mature by swimming.
abstract: 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.
  
  
  CONCLUSIONS
  Dopaminergic inhibition is thus not effective in males and swimming results in natural maturation, probably via GnRH-release.
authors.affiliation: Integrative Zoology, Institute of Biology, Leiden University (IBL), van der Klaauw Laboratory, Kaiserstraat 63, 2311 GP Leiden, The Netherlands. a.p.palstra@biology.leidenuniv.nl
authors.forename: Arjan P
authors.initials: AP
authors.lastname: Palstra
authors.forename: Denhi
authors.initials: D
authors.lastname: Schnabel
authors.forename: Maaike C
authors.initials: MC
authors.lastname: Nieveen
authors.forename: Herman P
authors.initials: HP
authors.lastname: Spaink
authors.forename: Guido Eejm
authors.initials: GE
authors.lastname: van den Thillart
mesh_terms: D000811:Anguilla / Q000254:growth & development* / Q000378:metabolism*; D000818:Animals; D005260:Female; D006066:Gonads / Q000254:growth & development* / Q000378:metabolism*; D037101:Luteinizing Hormone, beta Subunit / Q000378:metabolism*; D008297:Male; D012737:Sex Factors; D013091:Spermatogenesis / Q000502:physiology*; D013550:Swimming / Q000502:physiology*
chemical_list: D037101:Luteinizing Hormone, beta Subunit