Polytene chromosomes of the Old World screwworm fly (Chrysomya bezziana) and its evolutionary relationships with Lucilia cuprina and Cochliomyia hominivorax (Diptera: Calliphoridae)

Abstract

Standard polytene chromosome maps for the Old World screwsworm fly, Chrysomya bezziana, are presented. Good quality polytene chromosomes obtainable from pupal trichogen cells allow detailed analysis of autosomal euchromatin. The sex chromosomes are represented by irregular heterochromatic structures resembling those described previously in trichogen polytene chromosomes of the Australian sheep blowfly, Lucilia cuprina. A high degree of homology with the banding pattern of L. cuprina polytene chromosomes allowed direct recognition of approximately 60% of the L. cuprina complement in the C. bezziana maps. A further 13% may be homologous. The extensive homology observed is discussed in relation to the rate of chromosome rearrangement and conservation of karyotype elements in the evolution of Calliphorid flies. The observed conservation in polytene banding patterns should facilitate construction of phylogenies over a number of generic groups.Key words: Chrysomya bezziana, screwworm, polytene map, chromosome homology.