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Unusual Parasitic Wasp Discovered in 99-Million-Year-Old Amber: A bizarre trapping mechanism in a newly identified parasitic wasp dating back to the Cretaceous period has been revealed through specimens preserved in amber, offering insights into ancient insect evolution and behavior. This remarkable find sheds light on the diverse strategies employed by insects in prehistoric ecosystems.
Ancient Wasp with Venus Flytrap-like Abdomen Unearthed
Researchers have examined 16 specimens of a diminutive wasp, encased in amber from Myanmar, that lived approximately 99 million years ago during the age of dinosaurs. This previously unknown species, scientifically named Sirenobethylus charybdis, possessed a peculiar structure on its abdomen resembling a Venus flytrap. This biological marvel, detailed in the journal BMC Biology, likely functioned to ensnare other insects, effectively conscripting them as hosts for its offspring.
Lars Vilhelmsen, a wasp expert and curator at the Natural History Museum of Denmark, initially mistook the abdominal expansion for an air bubble when observing the first specimen. “Initially, observing the tip of the abdomen, I assumed it was simply an air pocket, a common occurrence in amber specimens,” Vilhelmsen stated. However, further examination of multiple specimens confirmed it to be an integral part of the ancient creature.
Vilhelmsen, along with colleagues from Capital Normal University in Beijing, determined the structure’s mobility. Its varied positions across different specimens indicated it was not fixed. “The lower flap of the structure was observed in both open and closed states, confirming its capacity for movement and suggesting a grasping function,” Vilhelmsen clarified.
Analogous to a Venus Flytrap
The research team drew parallels between the wasp’s trapping mechanism and the Venus flytrap, a carnivorous plant known for its snap-trap leaves. “To understand the function of a 100-million-year-old insect, we explore contemporary insect fauna for similar features. We searched for analogous structures within wasps and other insect groups,” Vilhelmsen explained.
“Surprisingly, no insect analog exists. We had to venture outside the animal kingdom, into botany, to find a remote resemblance to this extraordinary adaptation,” he added.
A detailed view of Sirenobethylus charybdis showcasing the Venus flytrap-esque structure on the wasp’s abdomen. – Qiong Wu
Parasitic Strategy: Host Manipulation
The scientists believe the wasp’s grasping structure was not designed for killing. Instead, they propose a strategy where the wasp would deposit eggs into the captured insect before releasing it. Subsequently, the parasitoid larvae would develop within or upon the unwitting host’s body, ultimately consuming it, according to Vilhelmsen. The host insect was likely of comparable size and capable of flight, he speculated.
While not identical, analogous parasitic behaviors are present in modern wasps. Cuckoo wasps, for instance, deposit eggs in other wasp species’ nests, where their larvae then devour the host’s young after hatching.
Amber Fossils: Windows to the Past
Amber fossils provide an exceptional, three-dimensional glimpse into deep time. Beyond plant and floral specimens, amber has preserved a diverse array of ancient life, including a dinosaur tail, crab, hell ant, spider mother with young, and a firefly, all entombed within ancient tree resin.
A fossil enthusiast acquired the amber containing Sirenobethylus charybdis from the Kachin region of Myanmar, near the Chinese border, years prior and gifted it to Capital Normal University’s Key Laboratory of Insect Evolution and Environmental Changes in 2016, the report stated.
Amber fossils have become increasingly significant in paleontology recently. However, ethical concerns have surfaced regarding the origin of amber from Myanmar. Following the 2021 military coup, some paleontologists advocate for a moratorium on researching amber originating from this region.
An artist’s depiction of Sirenobethylus charybdis exhibiting its unique grasping mechanism. – Xiaoran Zuo
“Cretaceous Weirdo” and Fossil Significance
Phil Barden, an associate professor at the New Jersey Institute of Technology, specializing in amber fossils, described Sirenobethylus charybdis as a “Cretaceous weirdo,” adding to the expanding catalog of insects from that era exhibiting “adaptations beyond the scope of creatures living today.”
Barden, who was not involved in the study, highlighted the find’s importance: “Despite approximately one million known insect species and their diverse living forms, the fossil record continues to reveal astonishing and unexpected novelties that surpass imagination,” he conveyed via email.
However, Barden noted that the Venus flytrap hypothesis remains “somewhat speculative, though plausible.”
“Evidence suggests the abdominal components possessed a clear range of motion. Furthermore, numerous setae, or hairs, appear strategically positioned to detect and potentially immobilize hosts,” Barden observed.
He suggested alternative functions for the biological structures, such as prey detection within soil or even wasp larvae transport.
Barden questioned the evolutionary necessity of this grasping mechanism: “Extant parasitoid wasp species effectively immobilize hosts without abdominal clasping. Why couldn’t these ancient wasps rely on stings or mouthparts for host capture, like their modern counterparts?”
Vilhelmsen emphasized the egg-laying organ’s proximity to the trap-like structure as a crucial factor in their interpretation. Nevertheless, due to all examined Sirenobethylus charybdis specimens being female, the researchers could not exclude a potential role in mating, according to the study’s findings.
Vilhelmsen concluded, “This discovery is truly unique and unexpected – something beyond my anticipation, a complete surprise. It is absolutely a remarkable find.”