Impact of multi-generational laboratory rearing on the development and viability of Cochliomyia hominivorax.

The screwworm fly, Cochliomyia hominivorax, is a significant pest in Brazil, posing threats to agriculture and public health. Laboratory rearing is crucial for developing control strategies like the sterile insect technique (SIT); but the effects of multi-generational rearing on the fly's biological parameters are not fully understood. This study investigated the impact of rearing C. hominivorax for 12 inbred generations on its morphometrics, reproductive capacity, and life expectancy. Specimens were collected at distinct developmental stages across 12 generations for morphometric analysis, and key viability traits were assessed through biological assays. Data were analyzed using linear mixed-effects models and Kaplan-Meier survival analysis. The results revealed that morphometric parameters and key reproductive traits (oviposition, egg weight, hatchability, and larval survival) remained stable across all generations (p > 0.05). However, a significant decline in adult life expectancy was observed (log-rank test, χ2 = 338.257, p < 0.001), becoming pronounced from the fifth generation onwards. Significant sexual dimorphism was also confirmed: males were larger and heavier (Mann-Whitney U = 9884.5, p < 0.001), while females exhibited significantly greater longevity (log-rank test, χ2 = 44.538, p < 0.001). Continuous laboratory rearing of C. hominivorax appears robust for maintaining physical and reproductive traits, but negatively impacts fitness-related traits like longevity, likely due to inbreeding. These findings provide a critical quantitative baseline for quality control in mass-rearing programs and highlight the need for strategies to manage genetic diversity in laboratory colonies to ensure their effectiveness for research and SIT applications.