Fig. 5
From: A review of the reproductive system in anuran amphibians
Male frog reproductive system. The fat bodies are above the testicles, both of which are located in the ventral region adjacent to the kidneys. The testicles consist of seminiferous tubules where spermatogenesis occurs, and interstitial space between the adjacent tubules. The seminiferous tubules are conformed by a seminiferous epithelium, connective tissue, and muscle cells. The seminiferous tubule houses the spermatogonia, spermatocytes, spermatids, and spermatozoa. Spermatogonia are usually large, voluminous, spherical cells. The spermatocytes have a smaller nucleus and differentiate into spermatids (long or round cells). Spermatids are located in the seminiferous tubule lumen and differentiate into spermatozoa. Spermatozoa morphology differs among frog species; (a) pointed head (Odontophrynus cultripes), (b) crescent-shaped (Afrixalus frog), (c) sickle-shaped head (Rhacophoridae), (d) S-shaped head (Nyctibatrachus major), (e) corkscrew-shaped head (Xenopus laevis), and (f) cane-shaped head (Polypedates maculatus)