Amber fossil reveals new clues to ancient cockroach ecology

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Studying the sensory organs of a 100 million year old cockroach offers new insights into how the species may have lived.


Photo of the entire amber-covered fossil specimen of Huablattula hui, a Cretaceous cockroach (Ryo Taniguchi, et al. The Science of Nature. September 28, 2021).

Researchers from Hokkaido University have revealed new information about an extinct cockroach species by studying the sensory organs of a specimen preserved in fossilized tree resin known as amber. Their findings, which were published in the journal The Science of Nature, suggest that extinct cockroach species may have had more diverse habitats and behaviors than their living relatives.

Animals rely heavily on their sensory organs to detect information about their environment, such as detecting food, habitats, predators, and mates. These organs are therefore crucial for their survival and evolution.

“Fossils provide the only direct source of evidence for tracing the diversity and evolution of sensory organs. However, insect organs are rarely preserved in sediment because they are so small and fragile,” says Ryo Taniguchi, a researcher in the Department of Natural History Sciences at Hokkaido University. “One way to solve this problem is to study exceptionally well-preserved fossil material from amber.”

The Hokkaido team, together with colleagues from Fukuoka University, analyzed the sensory organs of an extinct male cockroach species called Huablattula hui. They studied a specimen preserved in a piece of Myanmar amber believed to be around 100 million years old.

They used a combination of techniques, including photography, microscopy, X-ray CT scans, 3D modeling and thin sectioning, to observe the cockroach in high resolution and compare its characteristics to those of other species.

“The cockroach specimen was remarkably well preserved and showed many morphological features in great detail,” says Taniguchi.

The researchers found that, compared to dark species alive today, H. hui had relatively large, well-developed eyes. H. hui also had fewer receptors on its antenna to detect information such as smells, physical contact and temperature. Taken together, these observations imply that the species was active in bright, open environments during the day, unlike many extant cockroach species that live in dark habitats, such as forest floors, caves, or nocturnal environments.


Huablattula hui has larger eyes (left) and fewer antennal sensilla (right, asterisks) compared to modern cockroach species. This indicates that they were active in bright, open environments during the day (Ryo Taniguchi, et al. The Science of Nature. September 28, 2021).

They also found that the species has a large number of sensory receptors on its antennae that resemble those used by male mantis to detect sex pheromones. The number and pattern of the receptors suggests that H. hui may have used them to communicate between the sexes.

Taken together, these observations indicate that cockroaches living during the Cretaceous period, 145 to 66 million years ago, may have inhabited a wider range of environments than related species alive today.

This work shows that the study of amber animal fossils is a powerful tool for understanding the evolution of sensory systems.

Original article:

Ryo Taniguchi, et al. Reconstruction of the ecology of a Cretaceous cockroach: destructive and high resolution imaging of its microsensory organs. The science of nature. September 28, 2021.

DOI: 10.1007/s00114-021-01755-9

Funding:

This work was supported by the Kuribayashi Scholarship and Academic Foundation (2020-2-6), the Japan Society for the Promotion of Science (JSPS; JP20J00159, 19H02010) and the Canon Foundation (2019-4).

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