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← Theoretical B

Q17 — Incompatible Insect Technique and Wolbachia-Induced Cytoplasmic Incompatibility

Theoretical B Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Ecology

The incompatible insect technique (IIT) controls harmful insects by inducing mating incompatibility with the use of Wolbachia bacteria. Wolbachia kills embryos only when an infected sperm fertilizes an uninfected egg, while other combinations show no developmental issues. Aedes albopictus is a mosquito species with males as active gamete dispersers. A study on IIT effectiveness began with collecting Wolbachia-free fertilized eggs from the wild. After being reared in the lab, newly hatched mosquitoes were irradiated to sterilize only females. All mosquitoes were then infected with Wolbachia and released into experimental sites, while control sites received wild-type mosquitoes. Hatched eggs were counted, with their spatial distribution shown in Figure 1.

A satellite/aerial photo with a red polygon marking the experimental release site and a blue polygon marking the control site, overlaid with yellow circles of varying size marking hatched-egg counts. Figure 1. Spatial distribution of hatched eggs. The red polygon marks the experimental site, and the blue polygon marks the control site. Yellow circles indicate the number of hatched eggs (larger circles denote more eggs).

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. The average lifespan of males of Aedes albopictus positively correlates with the effectiveness of IIT.
B. Reducing the initial irradiation dose can lead to resistance against the Wolbachia strain in successive mosquito generations.
C. When 50% of males and females are infected (1:1 sex ratio), 75% of matings produce no offspring due to cytoplasmic incompatibility.
D. Mosquito migration from control site to experimental site is the most likely explanation of the hatched eggs found in the experimental site.
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Question reproduced from IBO 2024, Theoretical Exam Part B, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF