V. Loeschcke et al., CHROMOSOMAL VARIATION, SEGREGATION AND SEX DETERMINATION IN HYDROTAEA-MERIDIONALIS (DIPTERA, MUSCIDAE), Hereditas, 118(3), 1993, pp. 229-234
In addition to five pairs of euchromatic chromosomes common to all ind
ividuals, three different morphological types of heterochromatic chrom
osomes were found in Hydrotaea meridionalis: two acrocentric chromosom
es of different length and a smaller submetacentric chromosome that oc
cur in different combinations. The most common type, the larger of the
acrocentric chromosomes, occurred as a pair in 149 out of 197 larvae.
Mother-offspring combinations revealed that the larvae progeny of sev
eral mothers carried morphologically only the common karyotype. Despit
e existing morphological variation in karyotypes the same karyotypes w
ere found in male and female adult flies. This observation is interpre
ted by an autosomal sex-determining mechanism. As there was also found
a sex-specific karyotype in males, a simple hypothesis to explain the
observed distribution of karyotypes among sexes is suggested: one mal
e locus located on one of the autosomes with a dominant heterogametic
sex determination mechanism. Only in homozygous recessives for that lo
cus is sex determined by the independent XX/XY sex-determining system.