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Effects of advanced photoperiod cycle on the epidermis and gonadosomatic index of 2‐year‐old rainbow trout, Salmo gairdneri R., reared at natural temperature
Author(s) -
Nakari T.,
Soivio A.,
Pesonen S.
Publication year - 1986
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.1095-8649.1986.tb04960.x
Subject(s) - salmo , biology , epidermis (zoology) , rainbow trout , gonadosomatic index , photoperiodism , brown trout , sexual maturity , testosterone (patch) , zoology , anatomy , fish <actinopterygii> , fishery , endocrinology , botany , fecundity , population , demography , sociology
Sexual dimorphism was shown in the epidermis of 2‐year‐old rainbow trout. The changes in the epidermis which appear normally at the spawning time can be timed earlier by advancing the normal annual photoperiod cycle by three months. The epidermis of the advanced fish was significantly thicker than that of the control fish during the winter preceding spawning. For most of the year the epidermis of the males was thicker than that of the females, but females had more mucous cells in the epidermis than males. The maximum concentration of plasma testosterone coincided with the epidermal thickening.