Testicular histological examination of spermatogenetic activity in captive gorillas (Gorilla gorilla)

Abstract

To clarify the reproductive state of male gorillas, we performed histological examinations on the testicles of 10 male gorillas (Gorilla gorilla). The testicular samples were obtained by autopsy, and ordinal histological preparations were made for light microscopy. The poor spermatogenesis of this species was characterized by the following findings: First, spermatogenesis was evident in only four samples. Meiosis progressed in two samples, but they lacked spermatogenesis. In the remaining four specimens, seminiferous tubules hyalinized without any sign of spermatogenesis. Second, seminiferous epithelia were thin even in the males in which spermatogenesis was observed. Third, degenerated seminiferous tubules were found in all specimens. Fourth, abnormally large syncytial cells were found in the tubules. Six stages in the epithelial cycle of the seminiferous tubules were identified. Testosterone staining made it clear that there were many Leydig cells with spherical or fusiform nuclei in an abundance of interstitial tissue. The relevance of the testicular architecture of gorillas to the mating system is discussed.

A comparative study on testicular microstructure and relative sperm production in gorillas, chimpanzees, and orangutans

“…1a and b). As reported previously [Enomoto et al, 2004], in gorillas, the seminiferous epithelium in the gorilla is thin, with scattered spermatocytes and spermatids. The cycle of the seminiferous epithelial is divided into six stages according to the combination of spermatogenic cells.…”

“…For individuals without data on testicular size (G1, G4, C1, C2, O1, O2, and O4), we used the mean of total testicular volume in individuals with spermatogenesis. We calculated the total length of the seminiferous tubules (TLT) as follows: (total tubular volume) = (total testicular volume) × (proportion of the seminiferous tubules in cross‐sectional area) = (cross‐sectional area of a tubule) × TLT. Therefore, TLT = (total testicular volume) × (proportion of the seminiferous tubules in cross‐sectional area)/(cross‐sectional area of a tubule). In 30 tubules from the gorilla and chimpanzee, we counted the sperm or mature spermatids per tubule (ST) in stages I and II [Enomoto et al, 2004] of the cycle of the seminiferous epithelium. Stage I supersedes the second meiotic division and stage II precedes the release of sperm.…”

“…In 30 tubules from the gorilla and chimpanzee, we counted the sperm or mature spermatids per tubule (ST) in stages I and II [Enomoto et al, 2004] of the cycle of the seminiferous epithelium. Stage I supersedes the second meiotic division and stage II precedes the release of sperm.…”

“…Following pioneer studies by Clermont and Leblond [Clermont & Leblond, 1955, 1959], histological studies of the testis were performed in various primate species such as the human ( Homo sapiens ) [Clermont, 1963, 1966; Schulze, 1982; Schulze & Rehder, 1984; Schulze et al, 1986], chimpanzees ( Pan troglodytes ) [Smithwick & Young, 1996; Smithwick et al, 1996], gorillas ( Gorilla gorilla ) [Enomoto et al, 2004], and orangutan ( Pongo pygmaeus ) [Nakano et al, 2010]. However, there have been no phylogenetic studies comparing testicular microstructure among great apes.…”

The Y chromosome in the era of intracytoplasmic sperm injection: a personal review

“…Chimpanzees, which weigh only about 100 pounds, have enormous 8-cm-diameter round (not oval) testes with sperm counts of >1 billion/mL. Yet gorillas, which weigh as much as 600 pounds or more, have tiny testes, very poor spermatogenesis, and, in the sparse literature on gorilla testicular histology, in the majority of cases have what appears to be Sertoli cells only (151). Humans, the closest living relatives to chimpanzees and gorillas, fall somewhere in between.…”