Premium
Fish full life‐cycle testing for androgen methyltestosterone on medaka ( Oryzias latipes )
Author(s) -
Seki Masanori,
Yokota Hirofumi,
Matsubara Haruki,
Maeda Masanobu,
Tadokoro Hiroshi,
Kobayashi Kunio
Publication year - 2004
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/03-26
Subject(s) - oryzias , methyltestosterone , vitellogenin , biology , hatching , development of the gonads , fecundity , andrology , reproduction , secondary sex characteristic , fish <actinopterygii> , androgen , embryo , sexual maturity , ovary , sexual differentiation , medicine , endocrinology , gonad , zoology , hormone , ecology , population , fishery , genetics , environmental health , gene
We studied the chronic effects of methyltestosterone (MT) on reproductive status of medaka ( Oryzias latipes ) over two generations under continuous exposure to verify the applicability of the fish full life‐cycle test (FFLC) for this androgen with this species. The exposure of parental (F 0 ) medaka to MT was begun on embryos within 12 h postfertilization and continued for up to 101 d; assessment endpoints included embryological development, hatching, posthatch survival, growth, sexual differentiation, reproduction, and hepatic vitellogenin (VTG) levels under flow‐through exposure to MT at each mean measured concentration of 0.35, 1.09, 3.29, 9.98, and 27.75 ng/L. Eggs (F 1 ) spawned from the F 0 fish at 98, 99, and 100 d posthatch were examined for hatchability, survival after hatching, growth, sexual differentiation, and hepatic VTG level until 60 d posthatch. In the FFLC with medaka, MT induced masculinization of both secondary sex characteristics and gonads. We observed that all F 0 fish in the 27.75‐ng/L treatment group showed male secondary sex characteristics in which no fish with ovary could be discerned. Several fish with ovaries in F 0 and F 1 generations treated with 9.98 ng/L showed male secondary sex characteristics. We also observed swollen abdomens in the F 0 and F 1 female fish in the 9.98‐ng/L treatment group. These swollen abdomens were induced by enlarged ovaries and were accompanied with declined fecundity and fertility in the F 0 generation. These results indicate that MT reduces the reproductive potential of medaka and that the FFLC with this species is applicable to the evaluation of androgens.