phosphorusPyrrolizidine alkaloids are bitter, toxic, and difficult to pronounce. They are produced by several different types of plants and are one of the leading causes of accidental death in cattle.
Plants containing these alkaloids have made it clear they don’t want to be eaten, but that hasn’t stopped the Bella Moth (colorful ephemera). These sun moths specialize in alkaloid-rich leaves and seeds of rattlesnake plants. They then use toxins to protect their eggs and deter predators later in life. They even use it to create pheromones that attract the opposite sex.
Exactly how the bella moth and related species evolved the ability to safely consume pyrrolizidine alkaloids remains unknown.
In a new study published in the Proceedings of the National Academy of Sciences, researchers sequenced the bela moth genome, which they used to identify specific genes that may confer immunity to these toxins. They also sequenced the genomes of 150 museum specimens, some of which were more than a century old, to determine the origins of the bella moth and its close relatives. Finally, they combed through genetic data for clues that could help explain how the Bella moth’s intricate wing patterns evolved over time—the first study of a moth or butterfly to use dried specimens from museum collections.
“We have successfully demonstrated that you can use museum specimens to answer genetic questions that typically require complex laboratory techniques,” said study co-author Dr. Roberto M., Collections Coordinator of the McGuire Center for Lepidoptera and Biodiversity at the Florida Museum of Natural History. Andrei Sourakov said. “This opens a window for future studies of this type.”
Eggs are particularly vulnerable to predation. To prevent them from being eaten, Bella moths inject toxic alkaloids into their eggs.
Bella moth caterpillars are brightly colored and full of toxins.
Bella moths accumulate most of their toxins while eating plants as caterpillars. They retain this toxin during pupal metamorphosis and adulthood.
Bella moths have an ancient and unique wing pattern symmetry that makes them easily distinguishable from their close relatives.
Sourakov, who has been studying the bela moth for 15 years, said sequencing the species’ genome was a natural next step from the research he has conducted so far. Many of the insights he gained during that time came from his work with undergraduate and high school students, helping them conduct short experiments, analyze data for science fairs, and interpret results in peer-reviewed papers.
In one such project, a student set out to determine the average lifespan of an adult bela moth and accidentally stumbled across the Methuselah of the moth world. “To our surprise, their lifespan was up to 50 days, four to five times longer than ordinary moths,” Surakov said.
Longevity is not a crucial trait for most moth species. Many reproduce once and soon die from aging or predation. But Bella moths are not restricted by the latter, making it more likely that genes conferring longevity will be beneficial and passed on to the next generation.
“It makes sense for things that are chemically protected to live longer because even if they are caught, the predator usually lets go and the moths can keep flying around.”
Bella moths live in much of eastern North America, Central America, and the Caribbean, and are usually active during the day. Bella moths do not use darkness as cover to hide from predators, instead focusing on being seen. Their wings are covered in dazzling pink, pearly, onyx and sulphur-yellow scales, allowing birds and predatory insects to easily spot them from a distance. Any predator unlucky enough to catch a butterfly moth will quickly correct its mistake.
“Banana spiders will pick them out of their webs,” Surakov said, adding that wolf spiders and birds will go to great lengths to avoid them. “When they are caught, they produce a foul-tasting frothy liquid made almost entirely of alkaloids.”
When ready to mate, females release a cloud of aerosolized alkaloids derived from the plants they ate as caterpillars. Males are attracted to the scent and follow its source. There, they perform a brief but complex ritual, gently touching the female’s head with two fluffy and retractable structures that closely resemble dandelions. Each filament in these structures contains pyrrolizidine alkaloids.
When male bella moths try to attract a mate, they inflate two retractable air sacs called coremata.
If bella moths realize they are in danger, they emit a foamy toxin from their upper thorax to fight off predators.
The alkaloids are found in the stems and leaves of bella moth host plants (called rattleboxes), but are particularly concentrated in the seeds that the caterpillars specifically seek out.
If the female believes that the male has stored a sufficient quantity and quality of alkaloids, the pair will mate. When finished, the male leaves behind a parting gift called a seminal vesicle, which contains sperm and, yes, more alkaloids. The female uses this substance and her own reserves of alkaloids to inject toxins into the eggs she lays. This kind of biparental egg protection is rare among insects. In fact, when this was first observed in Bella moth adults in 1989, it was the only known example of a male moth or butterfly investing chemical resources into its offspring.
Bella moths are able to avoid the adverse effects of pyrrolizidine alkaloids by using a special enzyme to oxidize the molecule, rendering it harmless. However, if a predator eats a moth, the process is reversed and the alkaloids regain their potency.
Pyrrolizidine alkaloids likely first evolved as a defense mechanism in plants and then became commercially available to moths. Surakov and his colleagues wanted to know how the bella moths acquired this detoxifying enzyme and how they maintain it through a millions-year arms race between plants and moths.
The authors found that the bella moth possesses not one but two copies of the gene encoding its unique detoxifying enzyme. They may have acquired the second trait through a process of gene duplication, in which other species, including many plants, evolve new traits.
They also found two copies of some genes involved in antioxidant production and defense. Surakov suspects these genes may be involved in the Bella moth’s ability to detoxify alkaloids and its extraordinary longevity.
“Certain types of stress in biological systems can lead to longer lifespans. The interaction of bela moths with alkaloids may be not only the reason for their longevity, but also one of the mechanisms behind it.”
Jing Zhang, Qian Cong, Jinhua Shen, Leina Song and Nick Grishin of UT Southwestern Medical Center and Winnie Halllwachs and Daniel Janzen of Penn State are also study authors.
The research was funded in part by the Welch Foundation (grant numbers: I-2095-20220331 and I-1505), the National Institutes of Health (grant number: GM127390), and the Texas Cancer Prevention and Research Institute (grant number: RP210041).
Source: Andrei Surakov, asourakov@flmnh.ufl.edu
Media Contact: Jerald Pinson, jpinson@flmnh.ufl.edu, 352-294-0452
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Image Source : www.floridamuseum.ufl.edu