Annual morphological cycles of testis and thumb pad of the male frog (Rana ridibunda).

In this study, Rana ridibunda was used as samples because of their wide use in Turkey. Male frogs were collected in the East Marmara region each month throughout 1 year. Frogs from every monthly collection were used to analyze structural components of the thumb pads and testes. Spermatogenetic activity of Rana ridibunda living in the East Marmara region was determined to be "potentially continuous" type. Generally, the increase in the number and the size of nuclei of Leydig cells was inversely proportional to the fluctuation of spermatogenetic activity. The lumen of the seminiferous tubules in testes contained, in addition to the spermatogenic cells, a Periodic-acid Schiff-positive granular material. The amount of this material varied throughout the year, and that finding suggested a function related to spermiation. The components of thumb pads exhibited structural changes with respect to the activities of Leydig cells. During the periods where the Leydig cells were active, mucus glands (also called breeding glands) of thumb pads were also developed. On the other hand, we observed mixed glands with unknown function, which as first reported by us, and were poison glands in the thumb pads. The results suggest structural changes in the thumb pads are linked to changes in the testes.