The sexual segment of the kidney of a tropical rattlesnake, Crotalus durissus (Reptilia, Squamata, Viperidae), and its relationship to seasonal testicular and androgen cycles.

The sexual segment of the kidney (SSK) is a hypertrophied region of the nephron, which occurs in males of most squamate species that have been investigated, at least, during the active season. Many studies have shown that the SSK has a seasonal secretory cycle that could be correlated to the mating season, testicular activity, and androgen synthesis. However, to date, no study has investigated the presence of androgen receptors (AR) in cells of the SSK, nor the relation between the expression of AR, testosterone levels, and testicular condition.