Sperm head abnormalities in relation to the age and strain of mice.

Sperm abnormalities were examined in the samples of the uterine contents collected after copulation. Male mice of the inbred C57BL/Kw (C57), CBA/Kw (CBA) and KE strains were tested at the ages of 6, 7, 8 and 10 weeks. Severely misshapen spermatozoa were produced by 6-week-old males of all strains: 30% of spermatozoa had 'thread-like' heads, devoid of Feulgen-positive material; the total proportion of abnormalities was lowest in CBA males. During maturation the percentages of abnormalities dropped rapidly and the proportion of drastically misshapen spermatozoa diminished in favour of less severe deformations. The frequency distribution of abnormal sperm types was strain specific for adult males but not for very young males. Large spermatozoa were seen in samples from young CBA and KE males (0.5-2%) and sporadically in 10-week-old CBA males. A negative relationship between body weight and the severity of abnormalities was seen for young, but not adult, males reared in litters of different size. No sperm deterioration was noticed in the first year of life of 5 KE males tested every 3 months until death, but a male surviving to 15 months had increased (38%) proportions of abnormal spermatozoa.