CHROMOSOMES OF THE CARIBBEAN FRUIT FLY (DIPTERA: TEPHRITIDAE)
VARSOVIA E. CEVALLOS AND JAMES L. NATION
Department of Entomology & Nematology, University of Florida, Gainesville, FL 32611-0620
Larval tissues of Anastrepha suspensa
(Loew) (Diptera: Tephritidae) were examined to determine the optimal tissue and stage for chromosomal preparations and to determine the karyotype. Tissues were dissected in saline, stained in 2% aceto-orcein for 45 minutes, and squashed on a coverglass by thumb pressure. The compound eye imaginal discs from 6-dayold larvae yielded the best preparations of dividing cells. Mitotic figures also can be obtained from larval brain tissue, ventral nerve cord, and leg imaginal discs. In larvae 6 days old, many cells in the tissues examined were dividing. Cell division appears to be synchronized in the different tissues examined, with most cells in interphase or dividing at the same time during all instars. The male is heterogametic (XY) and the female is homogametic (XX). The chromosome number is 12 (10 autosomes + XX or XY). There are 3 pairs of subtelocentric and 2 pairs of submetacentric chromosomes. The X chromosome is subtelocentric and the Y chromosome is submetacentric. The two X chromosomes tend not to pair like the other chromosomes, and in males the Y chromosome often sticks to the short arm of the X chromosome.