Genetic Sexing Strains of Mediterranean Fruit Fly (Diptera: Tephritidae): Optimizing High Temperature Treatment of Mass-Reared Temperature-Sensitive Lethal Strains

Abstract

Genetic sexing systems based on a temperature-sensitive lethality have been developed for mass-reared Mediterranean fruit fly, Ceratitis capitata (Wiedemann). This study shows that the timing of high temperature treatment (34°C) of eggs of temperature sensitive lethal ( tsl ) C. capilata affects the number and accuracy of production of males. High-temperature treatment during late embryogenesis (24-48 h after egg collection) produced more male flies compared with treatment during early embryogenesis (0 -24 h after egg collection). The principal impact of the heat treatment was on egg hatch. Treatment during early embryogenesis resulted in 38.2%hatch, whereas treatment during late embryogenesis resulted in 55.5%hatch. Treatment during late embryogenesis conserved nearly all potential males, produced >99.5% males, and will improve the economy of male production for large scale tsl C. capitata rearing. Results support the existence of a maternal effect during the first 24 h of embryogenesis. Lethality in males occurred during the early part of embryogenesis, when male embryos were still dependent on the egg cytoplasm for development. Heat treatment did not eliminate aneuploid individuals as expected, but it did reduce a proportion of them. Some aneuploid individuals pupated, although many failed to emerge as adults. The frequency of aneuploid individuals increased throughout consecutive larval collections, resulting in decreased emergence and decreased pupal volume. These data suggest that it is not economical to collect larvae after day 3 or 4.