EUGENE M. MCCARTHY, PHD GENETICS
|Martin et al. measured dimensions (head length, head width, midpiece length, principal piece length, and total length) of spermatozoa in a variety of primates. Their results indicate that, when compared with other primates, the spermatozoa of humans and gorillas are about ten times more variable in form (334.5,Table 1).|
It is now well established that gorillas suffer from infertility far more often than is the case in other mammals. Thus, Martin et al. found that in the gorilla
|The two samples examined by Seuánez et al. were both taken from individuals that had fathered offspring. The semen examined may therefore have been of higher quality than that of the typical gorilla. Nevertheless, they found that 27 percent of the human, and 29 percent of the gorilla, spermatozoa were abnormal in some way or another (if not in shape, then at least with respect to other features, such as staining, cytoplasmic features, maturity, etc.).|
|McKenny et al.(1944) reported that smears from the testes of a 15-year-old captive gorilla showed no spermatozoa (328.7). Brandt (1972) records another case in which a gorilla failed to produce spermatozoa (81.6).|
If anything, gorillas are even less fertile than human beings. They commonly suffer from a condition known as testicular atrophy (or hypoplasia), which is seen in many interspecific hybrids. "Indeed, testicular hypoplasia and infertility is found throughout the literature on adult gorillas. Most often an aetiological [i.e., causative] factor for this infertility remains unknown" (Benirschke and Adams
|In general, Steiner observes, "Small external genitalia appear to be a constant finding in the gorilla, both wild and captive."|
|In Steiner et al. stated (538.4,5) that "no male [gorilla] in captivity is known to have reached sexual maturity, although the other three species of anthropoid apes have reproduced under similar living conditions." Of course, some captive gorillas have exhibited an ability to breed since this statement was made (1955). But even in 1981, Dixson (140.1) noted that "only three of the thirteen male gorillas in British collections are of proven breeding ability." The infertility of captive gorillas is such a problem that even expensive technical procedures such as in-vitro fertilization and gamete intrafallopian transfer have been deemed worthwhile (291.4; 322.2), and captive populations are still not self-sustaining (186.6; 456.7).|
Another case of testicular atrophy, this time in a captive gorilla, was reported four years later by Clarke.
In 1961 Inoue et al. examined a wild-caught 40-year-old male and stated that "both the penis and the testicles are remarkably small — the latter are sparrow's-egg-sized."
|The testicles described by Antonius et al. were same size as those of another captive gorilla, "Samson," examined by Short (509.15,8).|
Recently, Munson and Montali (1990) reported yet another case of testicular "degeneration" in a gorilla.
|Although Steiner et al. (538.4) suggested testicular atrophy may be due to malnutrition, Dixson and his colleagues (140.8) countered this supposition by noting that the most normal of the three sets of gorilla testicles they had examined belonged to "Oban" who was extremely malnourished after suffering from a gastrointestinal disorder for several years.|
Descriptions of testicular atrophy in gorillas are peculiarly reminiscent of accounts describing the testicles of the common mule and of other sterile, or partially sterile, hybrids. In comparing the testes of the mule with those of the horse, Makino
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