High Chromosome Number and Giant Postreductional Sex Chromosomes in the Beetle Walterianella venusta Schaufuss (Chrysomelidae, Alticinae)

Abstract

A high chromosome number for a coleopteran, 22-J-X+y, was encountered in an alticine, Walterianella venusta Schaufuss. The autosomes are very short, metacentric; the sex chromosomes very long and also metacentric. The sex chromosomes are desynaptic and postreductional in spermatogenesis. It is assumed that two trends operate in the evolution of the alticine chromosomes, first, the autosomal chromatin being incorporated repeatedly in the sex chromosomes, and second, the occurrence of the multiplication of the short autosomes.