title: Gonadal steroids affect LHRH preoptic cell number in a sex/role changing fish.
abstract: In diandric sex-reversing fishes, sexually active males and females (primary phase) regularly transform into an alternative reproductive morph, terminal-phase males, that are morphologically and behaviorally distinct. The transformation from primary to terminal phase is associated with a twofold increase in the number of luteinizing hormone-releasing hormone (LHRH) immunopositive cells in the forebrain preoptic area, a region involved in both the initial development and daily control of reproductive physiology and behavior. We now show that implants of 11-ketotestosterone induce increases in LHRH cell number in both primary phase sexes to the level observed in field-collected terminal phase males. Conversely, gonadal steroids had no effect on the number of LHRH preoptic cells in terminal phase males, suggesting that this is indeed a terminal stage in the development of this species. These results demonstrate that transition to the terminal phase by both sexes involves a parallel and convergent change in LHRH cell number, which utilizes an evolutionarily conserved mechanism of sexual differentiation: the inductive effects of gonadal steroid hormones.
authors.affiliation: Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853.
authors.forename: M S
authors.initials: MS
authors.lastname: Grober
authors.forename: I M
authors.initials: IM
authors.lastname: Jackson
authors.forename: A H
authors.initials: AH
authors.lastname: Bass
mesh_terms: D000818:Animals; D002452:Cell Count; D012734:Disorders of Sex Development; D004343:Drug Implants; D005260:Female; D005399:Fishes / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000032:analysis*; D006066:Gonads / Q000502:physiology; D008297:Male; D010858:Pigmentation; D011301:Preoptic Area / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D012727:Sex Characteristics; D012726:Sexual Behavior, Animal / Q000502:physiology; D012741:Sexual Maturation; D013739:Testosterone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D004343:Drug Implants; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; C003600:11-ketotestosterone