The multiple chromosomes of Paratylotropidia brunneri Scudder (Orthoptera: Acrididae)

Abstract

AbstractThere are 19 chromosomes in diploid cells of male Paratylotropidia brunneri; of these, four are V‐shaped multiples. There are twenty chromosomes in diploid cells of females; of these, four are V‐shaped multiples. If the two arms of each multiple are counted as separate chromosomes, we have the usual number of chromosomes for the Acrididae, i.e., twenty‐three in male and twenty‐four in female.There are nine chromosomes in the first spermatocyte divisions: seven tetrads, one octad and a decad. The latter is made up of the accessory chromosome associated with an octad.One of the V‐shaped multiples in the male is limited to that sex. The homologue of one of the dyads of which it is composed is a free dyad, the homologue of the other forms a V‐shaped multiple with the accessory chromosome. The V‐shaped multiple limited to the male shows differential heteropycosis in the prophases of the first spermatocyte. There is evidence that its homologous parts are isolated from each other as far as crossingover is concerned.A study of the first maturation division of the heterogametic sex is essential for the identification of the sex chromosome.