The penile smear: an index of sexual maturity in male golden hamsters.

Abstract

Spermatozoa appear on the glans penis of male golden hamsters at a mean age of 42.5 days of age. At this age, sperm have just begun to appear in the cauda epididymis. After their initial appearance sperm can be routinely recovered from the glans penis. The presence of penile spermatozoa is detectable by a rapid and convenient technique. The technique permits the identification of a specific age of sexual maturity in male hamsters with considerable accuracy. The penile smear technique is applicable to Norway rats also but apparently not to the house mouse. The discovery of a relationship between changes in vaginal cytology and the state of the ovary in rodents (Long and Evans, 1922) has facilitated extensive research on ovarian cyclicity and has provided a useful index of the onset of sexual maturity in females. For example, by using the vaginal lavage to identify first estrus in mice, Vandenbergh (1967, 1969) has shown that female sexual maturation can be markedly accelerated by the presence of a male or male pheromones. In contrast, male sexual maturation has received considerably less attention because of the absence of a discrete index of sexual maturity. The age at which males mature can only be arbitrarily assigned to a moment on the continuum of testicular growth and changes in secondary sexual characteristics (Fox, 1968; Reiter, 1968; Vandenbergh, 1971). Furthermore, the techniques available for measuring testicular development all involve either the death of the subject or considerable trauma from surgery or electroejaculation. The purpose of this report is to present a technique for evaluating male sexual maturity with ease and with essentially no trauma to the animal. This technique is based on observations by Orbach (1961) and Dr. Caryn Dupon (personal communication) that sperm can be routinely recovered from the glans penis of adult rats. Preliminary tests indicated that sperm could also be recovered from beneath the prepuce of the adult male golden hamster (Mesocricetus auratus) and as a result, an attempt was made to identify the onset of sexual maturity in male golden hamsters based on the presence or absence of penile sperm.