The Annual Testicular Cycle and Horn Casting in the Pronghorn (Antilocapra americana)

Abstract

Investigation of 55 pairs of testes from adult and yearling prong-horns ( Antilocapra americana ) indicated that diameter of interstitial cells and their nuclei, degree of spermatogenesis, and weight of testes were at an annual low during January and February. Testicular weight increased 2.5 fold by August. In April the epididymides were packed with spermatozoa and the interstitial cells reached maximal diameters. The epididymides remained full of spermatozoa until December, but the interstitial cells regressed from April to January. The testes of a 3-month-old fawn were infantile; the seminiferous tubules were without patent lumena and no stereocilia were present in the epididymides. A 5-month-old fawn had testes at the prepubertal stage; the lumena of the seminiferous tubules were patent and stereocilia were present in the epididymides. Hardening of new horny tissue began in September about the time testicular development was at its height. The horns were cast about 2 months after the rut while the testes were declining in weight.