One and done: The sperm-storing bug that settled in Florida

June 5, 2018
Stephenie Livingston
Institute for Food and Agricultural Sciences

The female cactus-feeding bug doesn’t need a male…for long.

After a single, quick mating session, the female cactus bug (Narnia femorata) — an insect that eats the fruit and pads of cacti — can store enough sperm inside her body to produce offspring for her entire lifetime, a new study shows.

So, what happens if she travels into new habitats? Well, she takes her luggage with her.

The study’s findings suggest a single female insect with the ability to store sperm can spark a colonization event or even invasive species outbreak, says study lead author Pablo Allen, an entomology postdoctoral researcher with the University of Florida’s Institute for Food and Agricultural Sciences.

Study authors, which included nine undergraduates, say the discovery may explain how the cactus bug recently spread through most of north-central Florida.

“Our work suggests that after only mating once, or for a brief period, a female cactus bug will be as productive as female insects that mate many times,” Allen said.

This discovery supports the idea that female insect fertility and mating habits should be more seriously considered by authorities developing pest management practices, which have focused on sterilizing males, Allen said. While the cactus bug has not been a problem in Florida, it has caused damage to the fruit industry in Mexico, where it eats the popular prickly pears (also called nopales).

To determine the viability of the cactus bug’s stored sperm, study researchers tracked the life-long fertility of females exposed to males for varying amounts of time. Egg production and fertility rates did not differ across experiments, suggesting that length of exposure to mates and number of mates has no effect on the female’s fertility or the number of babies she’ll have.

The study’s results offer clues as to the evolution of the sperm storage trait, which is common across a wide range of insects. Study authors suggest that environmental factors, like patchy distribution of male counterparts in space and time, resulted in some female insects evolving the ability to store sperm, Allen said.

In other words, mates can be hard to find for some bugs, so sperm is hoarded when found.

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