ANALYSIS OF SPERM QUALITY IN RECOMBINANT INBRED MOUSE STRAINS - CORRELATION OF SPERM HEAD SHAPE WITH SPERM ABNORMALITIES AND WITH THE INCIDENCE OF SUPPLEMENTARY SPERMATOZOA IN THE PERIVITELLINE SPACE

Recombinant inbred strains were developed from reciprocal crosses betw een two inbred strains of mice (CBA and KE) differing in sperm head sh ape, proportion of normal sperm heads (CBA, 95%; KE, 78%) and fertiliz ation efficiency (CBA, 100% of fertilized ova; KE, 72%), to determine whether the indices of sperm morphology and function were correlated. The following parameters were analysed in recombinant inbred and proge nitor strains: index of sperm head shape (head width in the middle of its length/head length), percentage of abnormal sperm heads, percentag e of spermatozoa with progressive movements, efficiency of penetration of hyaluronic acid polymer (Sperm Select(R)) and percentage of fertil ized ova after mating males from the tested strains with females from an outbred stock. For each investigated character, recombinant inbred strains, recombinant inbred EXCB and CBXE, could be divided into at le ast three categories: KE-like, CBA-like and intermediate, suggesting t hat in each case a minimum of two genes was involved. Recombinant stra ins derived from the reciprocal crosses of progenitor strains differed only with respect to the proportion of abnormal sperm heads, showing the involvement of the Y chromosome in determining this character. Pen etration into Sperm Select was significantly correlated both with fert ilization efficiency and sperm motility, while correlation with the pr oportion of normal spermatozoa did not reach the level of significance . However, there was a significant negative correlation of both sperm abnormalities and the incidence of supplementary spermatozoa in the pe rivitelline space with the index of sperm head shape. The results indi cate that these characters are genetically linked, or that sperm heads with a lower width to length ratio are more prone to undergo deformat ions during spermiogenesis, and are less efficient in establishing con tact with the vitellus after penetrating the zona pellucida.