Genetic linkage map of the Screwworm Fly (Cochliomyia hominivorax) (2n = 12)

The North American Screwworm fly (Cochliomyia hominivorax) is a Dipteran parasite of mammals, including humans and cattle. The eggs are laid in open wounds, and the screwworm larvae that hatch out eat the necrotic tissue, which can cause severe illness (myiasis) or death to the host. Eradication measures have included large-scale release of sterile male flies, and identification of insecticide-resistance genetic markers. As there are multiple strains of screwworms, biochemical markers can also be used to identify which strain is present in a particular area.

Phenotypic markers are shown shaded in blue, biochemical (allozyme) markers are unshaded. Numbers indicate percent recombination between markers.

Note for example the close linkage between the locus for the enzyme phosphoglucomutase (Pgm) and the phenotypic le and wh loci: presence of the latter in heterozygous recessive form can be monitored by screening for the Pgm allele. Note also that markers separated by ~50% recombination (Gpd - re, Cw - ye) will be difficult to distinguish from unlinked markers (50% recombination). Note also that each of the five autosomes are each about 100 cM long.

Figure ©2002 by Griffiths et al.; all text material ©2012 by Steven M. Carr