Female fruit flies cannot protect stored sperm from high temperature damage

Area of Science:

• Reproductive Biology
• Climate Change Ecology
• Insect Physiology

Background:

• Rising global temperatures pose a threat to population persistence.
• Heat-induced male sterility is a known consequence of climate change.
• The potential for female sperm storage to mitigate male infertility under heat stress remains under-explored.

Purpose of the Study:

• To investigate the capacity of female fruit flies to protect stored sperm from high-temperature stress.
• To compare the thermal tolerance of stored sperm in two fruit fly species: Drosophila virilis and Zaprionus indianus.

Main Methods:

• Exposing mated female fruit flies of two species to controlled high-temperature conditions.
• Assessing the fertility of stored sperm post-heat exposure through mating trials.
• Comparing fertility reduction in females versus direct heat damage to sperm in males.

Main Results:

• Sperm stored by female Drosophila virilis experienced near-complete sterilization at high temperatures.
• Sperm stored by female Zaprionus indianus showed only a slight reduction in fertility.
• Females of D. virilis recovered fertility upon remating, indicating sperm damage rather than female physiological damage.
• The temperatures causing fertility loss in mated females were lower than those damaging mature sperm in males.

Conclusions:

• Female sperm storage is unlikely to ameliorate climate change-induced male infertility.
• Female fruit flies are less effective than males at protecting sperm from heat stress.
• Female sperm storage exacerbates fertility costs of high temperatures, influencing population persistence during climate change.