Seasonal and Sex-specific mRNA Levels of Key Endocrine Genes in Adult Yellow Perch (Perca flavescens) from Lake Erie

To better understand the endocrine mechanisms that underlie sexually dimorphic growth (females grow faster) in yellow perch (Perca flavescens), real-time quantitative polymerase chain reaction (qPCR) was used to measure pituitary, liver, and ovary mRNA levels of genes related to growth and reproduction-sex in this species. Adult perch were collected from Lake Erie and body mass, age, gonadosomatic index (I-G), hepatosomatic index (I-H), and gene expression for growth hormone (GH), prolactin, somatolactin, insulin-like growth factor Ib (IGF-Ib), estrogen receptor alpha (esr1), estrogen receptor beta a (esr2a), and aromatase (cyp19a1a) were measured. Females had higher body mass, I-H, and liver esr1 mRNA level than males, while males had higher liver IGF-Ib, liver esr2a, and liver cyp19a1a mRNA levels. In both sexes, season had a significant effect on GH and liver IGF-Ib mRNAs with higher levels occurring in spring, which also corresponded with higher liver cyp19a1a mRNA levels. For females, IG, liver esr1, and ovary cyp19a1a mRNA levels were higher in autumn than the spring, and ovary cyp19a1a mRNA levels showed a significant negative correlation with pituitary GH and liver IGF-Ib mRNA levels. The most significant (p <= 0.001) relationships across the parameters measured were positive correlations between liver IGF-Ib and esr2a mRNA levels and liver IGF-Ib and cyp19a1a mRNA levels. This study shows significant effects of season and sex on adult yellow perch endocrine physiology.