Some moths use lethal toxins to deter predators and attract mates

Pyrrolizidine alkaloids, complex and toxic compounds produced by various plant species, have historically posed significant risks to cattle due to their lethal nature. Despite their toxicity and the clear signals from plants that contain these alkaloids discouraging consumption, bella moths (Utetheisa ornatrix) have uniquely adapted to not only consume these substances but also utilize them as a defense mechanism and a means to attract mates.

Genetic adaptations of bella moths 

In a new study led by the Florida Museum of Natural History, scientists have explored the genetic adaptations that allow bella moths to thrive on a diet rich in these dangerous compounds. 

The research, which involved sequencing the bella moth genome and analyzing genetic data from over 150 museum specimens, some over a century old, aimed to discover the evolutionary origins of bella moths and their close relatives, as well as the development of their distinctive wing patterns.

“We’ve managed to show that you can use museum specimens to answer genetic questions that normally require complicated laboratory techniques,” explained study co-author Andrei Sourakov, collections coordinator at the McGuire Center for Lepidoptera and Biodiversity. Sourakov, who has dedicated 15 years to studying bella moths, emphasized the significance of genome sequencing in advancing our understanding of these resilient insects.

Unique survival strategy of bella moths

The findings reveal that bella moths, which inhabit regions across eastern North America, Central America, and the Caribbean, exhibit a unique survival strategy by being conspicuously visible during the day instead of hiding from predators. 

Deterring predators 

Their vibrant wing colors serve as a warning about their toxicity, effectively deterring potential predators such as spiders and birds.

“Banana spiders will cut them out of their webs,” Sourakov said, adding that wolf spiders and birds will avoid them. “When caught, they produce foaming liquid that tastes bad made almost entirely out of alkaloids.”

Attracting mates

This defense mechanism is further found during mating, where females emit a plume of alkaloid-rich aerosols to attract males. 

The mating process involves the male moth transferring not only sperm but additional alkaloids to the female, which she uses to protect her eggs.

Complex evolutionary process 

The study not only sheds light on the unique dietary adaptations of bella moths but also underscores the broader implications of their survival tactics. The discovery that bella moths possess multiple copies of the gene responsible for their alkaloid detoxification enzyme suggests a complex evolutionary process that may have involved gene duplication, a phenomenon observed in various other species as well.

According to the researchers, the interaction with pyrrolizidine alkaloids could be a key factor behind the bella moth’s unusually long lifespan, as the stress imposed by these toxins may activate biological mechanisms that contribute to longevity.

“Certain types of stress on biological systems result in a longer lifespan. It could be that the interaction bella moths have with alkaloids is not only the reason why it makes sense for them to live long lives, but also one of the mechanisms behind it,” Sourakov speculated.

This study, published in the journal Proceedings of the National Academy of Sciences, both deepens our understanding of the complex interplay between bella moths and their toxic environment and opens new avenues for research into how other species adapt to and exploit toxic substances within their ecosystems.

More about bella moths 

Bella moths are strikingly colored moths found primarily in the Americas. Their vibrant wings are a mix of pink, white, and yellow hues with black spots, serving as a warning to predators about their toxicity. This toxicity is derived from their larval diet of plants in the Crotalaria genus, which contain poisonous alkaloids that the larvae retain into adulthood.

The bella moth’s life cycle is closely intertwined with its host plants. The female moth lays eggs on the underside of leaves, which hatch into larvae that feed on the toxic leaves, gaining their own chemical defenses against predators. This adaptation showcases a fascinating example of coevolution between the bella moth and the plants it depends on.

In addition to their ecological role, bella moths contribute to their ecosystem by participating in pollination. Their bright coloring not only warns predators but also attracts the attention of researchers and nature enthusiasts, making them a subject of interest in studies of evolutionary biology and ecology.

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