Variations in the vitellogenin titre during the reproductive cycle of Rana esculenta L.

1. Vitellogenin titre has been measured by rocket immunoelectrophoresis in specimens of Rana esculenta L. caught at three different locations in southern Italy. 2. Variations in the serum level of vitellogenin are temporally related to ovarian growth during the reproductive cycle. 3. With the exception of the FL population, vitellogenin titre is low at spawning time but increases prior to ovarian recovery. 4. It eventually levels off, or undergoes a slight decline during winter, when the ovary is in a static phase. 5. The evidence presented in this study is consonant with the experimental model on hormonal control of vitellogenesis. 6. The vitellogenin patterns observed in the populations examined in this study are interpreted as due to different environmental conditions even though the hybridogenetic nature of Rana esculenta has also to be taken into account.