Seasonal steroids variations and maturity stages in the female chub, Leuciscus cephalus L. (Pisces, Cyprinidae)

Abstract

Biometric evaluation, ovary histomorphometry, plasma 17β‐estradiol (E₂) and androgens (A) concentrations were investigated through the gonadal maturation and spawning of the wild chub, Leuciscus cephalus. A lower concentration of plasma E₂ was recorded from January (oogonia) to March (previtellogenic oocytes), while estradiol concentrations increased in April, when the ovary mostly contained vitellogenic oocytes. In July, when it was prevalently composed of post‐ovulatory follicles, there was a decline in E₂ plasma concentrations. Low concentrations of this steroid remained in the plasma until January, while high concentrations of androgens reached a peak in February and April preceding and following E₂. The observed seasonal changes in plasma steroids, reflecting the pattern of follicles size development, were to a large extent consistent with observations made in other cyprinids. Since they define the reproductive cycle of the European female chub, they will be useful in the construction of a maturity schedule for wild populations.

Keywords:

• Cyprinid
• chub
• Leuciscus cephalus
• reproductive cycle
• steroids

Acknowledgments

Many thanks are due to Dr. Massimo Rampacci (AGEI–Roma) for assistance during sampling, identifying and stocking of fish. This work was supported by a grant from Federico II University, Naples, Italy.