STUDIES ON THE KARYOTYPE AND GAMETOGENESIS IN TRICHURIS-MURIS

The cytological study of males and females of Trichuris muris (Schrank , 1788) revealed the diploid number of chromosomes to be 2n=6. The sex determining mechanism was XXfemale/XYmale. All the chromosomes were s ubtelocentric. Sex chromosomes formed the smallest pair, but X and Y w ere difficult to distinguish morphologically. Chromosome changes durin g gametogenesis in both sexes followed a classical pattern except in t he male prophase and metaphase I. Four male autosomes formed two bival ents, each with one proximal chiasma with strict localization, while s ex chromosomes X and Y formed two univalents. Female chromosomes forme d three rod bivalents of normal type, which possessed three, two and t wo chiasmata.