Testicular histology of implanted frogs. Representative testicular histology of frogs implanted with (A, D) Ch, (B, E) DHT, or (C, F) E2. (A, B, C) Testes from animals implanted for 10 days. (D, E, F) Testes from animals implanted for 30 days. Red arrow = I SPG; dark blue arrow = II SPG; light blue arrow = I SPC; yellow arrow = II SPC; green arrow = spermatozoa. Note DHT and E2 had no visible effects on testes of animals implanted for 10 days (A, B, C). In contrast, DHT and E2 visibly altered the germ cell composition in animals implanted for 30 days (D, E, F). Note the prominent spermatozoa and the absence of I SPC and II SPG in both DHT- and E2-treated testes (E, F). Scale bar = 100 μm.