Chromosomes and spermatozoa of the African great apes.

We have analysed the chromosome constitution of 8 chimpanzees (Pan troglodytes), 3 pygmy chimpanzees (Pan paniscus), and 16 gorillas (Gorilla gorilla). In the chimpanzees, the frequency of brilliant Q-band polymorphisms accounted for 8.85 regions per individual, and in the gorilla 14.9, whereas in man it was only 2.9-4.6. Variation in the amount of constitutive heterochromatin was also observed, and the gorilla appeared to be the most variable of all. A detailed analysis of the spermatozoa of the African apes showed that the gorilla produced pleiomorphic spermatozoa. As the animals under investigation were phenotypically normal, of proven fertility, and were kept in unheated cages, it is probable that gorillas, like human males, normally exhibit pleiomorphic spermatozoa. This makes it unlikely that clothing-induced hyperthermia could account for pleiomorphic spermatozoa in man. The modal cell types in the ejaculates of men and gorillas were also morphologically identical. The less frequent cell types defined as morphologically abnormal spermatozoa were also very similar and occurred in similar proportions. It is therefore impossible to distinguish between man and the gorilla by a simple examination of the ejaculate, although it is possible to distinguish between man and the chimpanzees or between the gorilla and the chimpanzees. Both species of chimpanzee produced identical spermatozoa. With quinacrine fluorescence, F-bodies were observed in the sperm head of the chimpanzees and the gorilla. In the chimpanzee and the pygmy chimpanzee, F-bodies correspond to brilliant autosomal regions, whereas in the gorilla they probably correspond both the the autosomes and the Y chromosome. There was no consistently visible F-body in the sperm head of the chimpanzee or the gorilla; in the pygmy chimpanzee, one fluorescent region appeared, and it probably corresponded to a brilliant region in autosomal pair No. 23.