title: Comparative Study of Growth and Gonad Maturation in Diploid and Triploid Marine Medaka,Oryzias dancena.
abstract: The marine medaka,Oryzias dancenais a suitable sample as a laboratory animal because it has a small size and clearly distinguishes between female and male. Data on the growth and maturity of the diploid and triploid sea cucurbit species suitable for laboratory animals are very useful for studying other species. Triploidy was induced in the marine medaka by cold shock treatment (0°C) of fertilized eggs for 45 min, applied two minutes after fertilization. The diploid and triploid male fish were larger than their female counterparts (P<0.05), and the concentrations of thyroid stimulating hormone (TSH) and thyroxine (T4) were higher in the induced triploids over 1 year (P<0.05). In both the diploid and tri-ploid groups the concentrations of TSH and T4 were higher in the male fish than in the females (P<0.05), while the testo-sterone and estradiol-17ß concentrations in the induced triploids were lower than in the diploids (P<0.05). The gonadosomatic index (GSI) of the triploid fish was lower than that for the diploids, and the GSI for females in each ploidy group were higher than that for the males. For both groups the GSI was highest at 4 months of age, and decreased thereafter to 12 months. Analysis of the gonads of one-year-old triploid fish suggested that the induction of triploidy probably causes sterility in this species; this effect was more apparent in females than in males.
authors.affiliation: Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea.
authors.forename: In-Seok
authors.initials: IS
authors.lastname: Park
authors.affiliation: Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea.
authors.forename: Hyun Woo
authors.initials: HW
authors.lastname: Gil
authors.affiliation: Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea.
authors.forename: Tae Ho
authors.initials: TH
authors.lastname: Lee
authors.affiliation: Institute of Marine Living Modified Organism (iMLMO), Pukyung National University, Busan 48513, Korea.
authors.forename: Yoon Kwon
authors.initials: YK
authors.lastname: Nam
authors.affiliation: Institute of Marine Living Modified Organism (iMLMO), Pukyung National University, Busan 48513, Korea.
authors.forename: Dong Soo
authors.initials: DS
authors.lastname: Kim
keywords: Growth hormone; Marine medaka; Oryzias dancena; Sex hormone; Sterility; Triploid