Comparative Studies on the Reproduction and Related Hormones in Fish and Coral
Guan-Chung Wu, Shinya Shikina, Ching-Fong Chang*
Department of Aquaculture, National Taiwan Ocean University; The Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung 20224, Taiwan.
We have been conducted comparative studies on the reproduction and hormones in fish (protandrous black porgy, Acanthopagrus schlegelii) and scleractinian coral (Euphyllia ancora). In fish, the hypothalamic-pituitary-gonadal axis releases GnRH, LH/FSH and sex steroids (estradiol, testosterone, 11-ketotestosterone, 17,20ß-dihydroxy-pregnen-3-one, 17,20ß,21-trihydroxy-4-pregnen-3-one) controlling seasonal reproduction, vitellogenesis, gamete growth and maturation. In southern Taiwan, mass spawning of scleractinian corals occurs during the lunar mid-March. We hypothesize that the endocrine system and hormones play important roles as endogenous factors, which synchronize mass spawning in corals and seasonal spawning in fish. Presence of aromatase activity was found in the coral tissue using tritiated-androstenedione as a substrate and tritiated H2O formation. A significantly high aromatase activity was detected during the spawning period in coral. Testosterone and estradiol in the free and glucuronided forms were also identified and detected continually throughout the year in the coral polys. Peak levels of free estradiol and glucuronided estradiol were observed in the coral tissue just prior to spawning. Free estradiol was always higher than glucuronided estradiol throughout the year in the coral. In contrast, the concentration of glucuronided estradiol was higher than free estradiol and glucuronided testosterone in seawater during coral mass spawning. Furthermore, immunoreactive and biological active gonadotropin-releasing hormone (irGnRH)-like peptide were also detected and peaked in coral during the spawning. Coral extracts and mammalian (m)GnRH agonist had a similar dose dependent effect on the release of LH in the black porgy fish pituitary cells; while mGnRH receptor antagonist specifically blocked the stimulatory effects of coral extracts. Our recent studies also demonstrated presence of transcript and protein of a steroidogenic enzyme, 17ß-hydroxysteroid dehydrogenase type 14 in coral. We also found the vitellogenesis and progesterone membrane receptor-like protein in coral. In conclusion, presence and changes of these biological components in coral suggest important roles in the control of reproduction and mass spawning in corals. Conserved hormones and signaling pathways highlight importance of conserved mechanisms in the regulation of the reproduction and spawning in both vertebrates (fish) and invertebrate (corals). More comprehensive studies in coral are required for better understanding of coral reproductive hormones and their signaling, and the evolution of reproductive hormones and signaling in metazoans.
Key Words: fish, coral reproduction, reproductive hormone
Guan-Chung Wu, Shinya Shikina, Ching-Fong Chang*
Department of Aquaculture, National Taiwan Ocean University; The Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung 20224, Taiwan.
We have been conducted comparative studies on the reproduction and hormones in fish (protandrous black porgy, Acanthopagrus schlegelii) and scleractinian coral (Euphyllia ancora). In fish, the hypothalamic-pituitary-gonadal axis releases GnRH, LH/FSH and sex steroids (estradiol, testosterone, 11-ketotestosterone, 17,20ß-dihydroxy-pregnen-3-one, 17,20ß,21-trihydroxy-4-pregnen-3-one) controlling seasonal reproduction, vitellogenesis, gamete growth and maturation. In southern Taiwan, mass spawning of scleractinian corals occurs during the lunar mid-March. We hypothesize that the endocrine system and hormones play important roles as endogenous factors, which synchronize mass spawning in corals and seasonal spawning in fish. Presence of aromatase activity was found in the coral tissue using tritiated-androstenedione as a substrate and tritiated H2O formation. A significantly high aromatase activity was detected during the spawning period in coral. Testosterone and estradiol in the free and glucuronided forms were also identified and detected continually throughout the year in the coral polys. Peak levels of free estradiol and glucuronided estradiol were observed in the coral tissue just prior to spawning. Free estradiol was always higher than glucuronided estradiol throughout the year in the coral. In contrast, the concentration of glucuronided estradiol was higher than free estradiol and glucuronided testosterone in seawater during coral mass spawning. Furthermore, immunoreactive and biological active gonadotropin-releasing hormone (irGnRH)-like peptide were also detected and peaked in coral during the spawning. Coral extracts and mammalian (m)GnRH agonist had a similar dose dependent effect on the release of LH in the black porgy fish pituitary cells; while mGnRH receptor antagonist specifically blocked the stimulatory effects of coral extracts. Our recent studies also demonstrated presence of transcript and protein of a steroidogenic enzyme, 17ß-hydroxysteroid dehydrogenase type 14 in coral. We also found the vitellogenesis and progesterone membrane receptor-like protein in coral. In conclusion, presence and changes of these biological components in coral suggest important roles in the control of reproduction and mass spawning in corals. Conserved hormones and signaling pathways highlight importance of conserved mechanisms in the regulation of the reproduction and spawning in both vertebrates (fish) and invertebrate (corals). More comprehensive studies in coral are required for better understanding of coral reproductive hormones and their signaling, and the evolution of reproductive hormones and signaling in metazoans.
Key Words: fish, coral reproduction, reproductive hormone