Further Observations on the Somatic Chromosome Cytology of Some Mosquitoes (Diptera: Culicidae)1

Abstract

The morphology of mitotic chromosomes from brain tissues of young fourth-instar larvae was studied in 6 mosquito species: Eretmapodites chrysogaster Graham, Aedes (Ochlerotatus) sierrensis (Ludlow), A. (Stegomyia) mascarensis MacGregor, A. (S.) polynesiensis Marks, A. (S.) simpsoni (Theobald), and A. (S.) vittatus (Bigot). As with other mosquito species (particularly culicines), differences between individual karyotypes were rather small. In all of these the diploid chromosome number was 6, the complement consisting of 2 relatively large pairs and 1 slightly shorter pair. In several species, prophase chromosomes were frequently polarized; these may possess distinctive, and therefore mappable, chromomere patterns in some species. Among the chromosomal aberrations observed in A. simposoni were a trisomic cell, probably resulting from mitotic nondisjunction, and a rather pronounced heteromorphism of the smallest chromosome in 1 cell. As aedine mosquitoes have more-or-less similar karyotypes, and as their salivary gland chromosomes have not been mapped thus far, examination of the chromosomes of intra- and interspecific hybrids is greatly needed.