Comparison of estradiol, testosterone, vitellogenin and cathepsin profiles among young adult channel catfish (Ictalurus punctatus) females from four selectively bred strains

Abstract

Potential variation in reproductive performance as young broodfish among four selectively bred strains of channel catfish was evaluated by comparing profiles of plasma estradiol, testosterone, and vitellogenin, and activities of cathepsin D, L, and B in follicle-enclosed oocytes during vitellogenesis in 2- to 3-yr-old females. No differences among the four strains were detected for any of the parameters measured. Plasma steroid concentrations demonstrated temporal differences, with testosterone levels peaking in January and estradiol levels peaking in April. Monthly changes in circulating vitellogenin concentrations coincided with oocyte growth. Average oocyte size in May, the typical time of spawning, was smaller (1624 μm) than that considered normal for mature oocytes (approx. 3000 μm) in this species. Furthermore, only 9% of the females in this study spawned, and no significant correlations could be determined between the reproductive indices and spawning success. Activities of cathepsin D, L, and B were also similar between the four strains of catfish. Cathepsin L activity was highest in March, and cathepsin D activity was highest in March and May. Cathepsin B activity was generally lower than the activities of either cathepsin L or D, with the highest levels occurring in November, December, and March. This is the first report of cathepsin activities and their relationships to other reproductive parameters in channel catfish.