title: Opposite-directional sex change in functional female protandrous anemonefish, Amphiprion clarkii: effect of aromatase inhibitor on the ovarian tissue.
abstract: BACKGROUND
  The anemonefish, Amphiprion clarkii, is a protandrous hermaphrodite. Under appropriate social conditions, male fish can become female. Previous studies indicated that estrogens are important regulators of sex change in this fish. However, the mechanism of sexual plasticity in the gonad of this fish is still unknown. To elucidate the mechanisms underlying the sexual plasticity in the ovary of female anemonefish, an aromatase inhibitor (AI, 500 μg/g diet) was administered to the functional female fish for 80 days.
  
  
  RESULTS
  The levels of estradiol-17β (E2) in the fish treated with AI were significantly lower than those in the control group. Three out of five fish had ambisexual gonads with active spermatogenic germ cells in the ovarian tissue. However, female fish in the AI-treated group prior to treatment and those in the control group displayed no testicular characteristics in their developed ovaries. This result strongly suggests that germ cells with bipotentiality or spermatogonial cells remain in the functional ovaries of anemonefish following sex change from functional males to functional females. There is a possibility that estrogen depletion due to AI treatment might have caused the opposite-directional sex change from functional female to male in the anemonefish.
  
  
  CONCLUSIONS
  The anemonefish keeps their high sexual bipotential in the ovary after sex change.
authors.affiliation: Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Sesoko 3422, Motobu, Okinawa 905-0227 Japan ; Okinawa Churashima Foundation, 888 Ishikawa, Motobu, Okinawa 905-0206 Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Sesoko 3422, Motobu, Okinawa 905-0227 Japan.
authors.forename: Saori
authors.initials: S
authors.lastname: Miura
authors.affiliation: Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Sesoko 3422, Motobu, Okinawa 905-0227 Japan ; Okinawa Churashima Foundation, 888 Ishikawa, Motobu, Okinawa 905-0206 Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Nozu
authors.affiliation: Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Sesoko 3422, Motobu, Okinawa 905-0227 Japan ; Ushimado Marine Institute (UMI), Faculty of Science, Okayama University, Ushimado, Setouchi, 701-4303 Japan.
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Kobayashi
keywords: Anemonefish; Aromatase; Estrogen; Protandrous hermaphrodite; Sex change