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Plasma and ovarian thyroxine levels in relation to sexual maturation and gestation in female Sebastes inermis
Author(s) -
Kwonm J. Y.,
CHANG Y. J.,
Sohn Y. C.,
Aida K.
Publication year - 1999
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1999.tb00836.x
Subject(s) - vitellogenesis , biology , rockfish , gestation , oviparity , embryo , medicine , endocrinology , ovary , sebastes , sexual maturity , embryogenesis , scorpaenidae , andrology , pregnancy , oocyte , zoology , fish <actinopterygii> , fishery , genetics
Plasma T 4 (L‐thyroxine) concentrations in the viviparous rockfish Sebastes inermis showed a peak (119·3±27·8 ng ml −1 ) during the development of embryos. Ovarian T 4 concentrations increased during vitellogenesis and final maturation and decreased during embryogenesis.However, total T 4 content within the ovary increased continuously up to the larval stages. Plasma oestradiol‐17β, (E 2 ) concentrations peaked at the final maturation stage and then recovered to the level seen during the non‐reproductive periods. Plasma testosterone (T) concentrations showed a peak (5·33±1·08 ng ml −1 ) at the embryo stage and high levels were maintained throughout the gestation period. Plasma T 4 concentrations during the embryo stage and ovarian T 4 content during vitellogenesis were much higher than the levels reported in oviparous fishes. These data suggest that in viviparous rockfish, T 4 may be required for sustaining gestation or embryo development within the maternal body. In addition, the high content of total T 4 in the ovary implies that there probably does exist a maternal‐embryo relationship during gestation as well as during vitellogenesis.