Twins and Teratisms in Rhesus Monkeys

Abstract

Birth records were kept on 1003 monkeys (Macaca mulatta) in free-ranging colonies on islets near Puerto Rico and in caged colonies in San Juan. Only one set of twins (males) was born. Major teratisms occurred in only 3 infants. One consisted of skeletal anomalies of a forelimb. Another involved anomalies of the genitalia; there was no vaginal opening or scrotum but a small phallus; and laparotomy revealed neither male nor female sex organs. However, the chromosomes of cultured leukocytes were those of a normal male. The third teratism had marked multiple facial anomalies, webbed digits, and a deformed wrist. The chromosomes were normal. Several other newborn monkeys had minor defects, such as partial webbing of digits or supernumerary nipples.