Chromosome Number and Sex-determining Mechanism in the Dragonfly Hemianax ephippiger (Burmeister)

The chromosome number of Hemianax ephippiger (Burmeister) has been recorded for the first time. The diploid chromosome number in both males and females is 14. The sex-determing mechanism is of XX:XY type. The X-chromosome is the largest of all and in the spermatogonial metaphase plate, it is markedly bent. The Y-chromosome is medium sized and rodshaped. Metrical study of fifteen metaphase I plates reveals two very long, ten medium and two very short chromosomes. The m-chromosomes are the smallest of all. The X- and Y-chromosomes both possess euchromatic regions which form pairing segments at meiosis. Anaphase I results in two types of daughter nuclei, one with X- and the other with Y-chromosome. Anaphase II is equational for the sex and all other chromosomes.