Studies on the Chromosome Behaviour in Three Species of Indian Homoptera

Abstract

SUMMARYThe chromosomes in the three species of the family Membracidae, subfamily Centrotinae, have been studied in this paper. Of these, Oxyrhachis tarundus Fabr. and Otinotus lignicola Buckt. show the same diploid number of 21 chromosomes and Gargara mixta Buckt. shows 19 chromosomes in the males. The sex determining mechanism is of XO:XX type in the three species.During the earlier phases of meiosis, the X chromosome is seen as a small heteropycnotic body, occupying a more or less central position. During the first meiotic metaphase, this chromosome remains further away from the autosomal bivalents in Oxyrhachis and Otinotus only. The lagging nature of the sex chromosome is observed at anaphase I in Oxyrhachis and Otinotus.The first division is reductional and the second division is equational for the sex chromosome in all the three species.The primitive sex determining mechanism in the order has been assumed to be the XO type and the type number for the family to be 21. Metrical studies of individual c...