99 million-year-old bioluminescent beetle found preserved in amber | Paleontology



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Found in a piece of mid-Cretaceous amber in northern Myanmar, the wonderfully preserved male of Azari cretophengodes has a light organ on the abdomen which presumably served a defensive function.

An artistic reconstruction of Cretophengodes azari;  the female larviform in the background is reconstructed from the existing beetles Phengodidae and Rhagophthalmidae.  Image credit: Li et al., Doi: 10.1098 / rspb.2020.2730.

An artistic reconstruction of Azari cretophengodes; the female larviform in the background is reconstructed from the existing beetles Phengodidae and Rhagophthalmidae. Image Credit: Li et al., doi: 10.1098 / rspb.2020.2730.

Bioluminescence, the production of light by living organisms, has evolved more than 30 times independently on various branches of the tree of life, including algae, cnidarians, fish and marine worms.

On earth, light-producing beetles are the most common and abundant bioluminescent organisms. Their elaborate flash displays play a role in mating recognition as well as signaling, communication, and prey attraction.

The majority of these beetles – more than 2,300 species – belong to the megadiverse superfamily Elateroidea (fireflies, fire beetles, glowworms).

The evolution of bioluminescence in these beetles is associated with unusual morphological changes, such as soft body and neotenia (retardation or slowing of physiological development), but the fragmentary nature of their fossil record reveals little about the origin of these adaptations.

“Most light-producing beetles are soft-bodied and quite small, and therefore have low fossil counts,” said Dr Chenyang Cai, a researcher at the School of Earth Sciences at the University of Bristol. and the Nanjing Institute of Geology and Paleontology. and the Center of Excellence for Life and Paleoenvironment of the Chinese Academy of Sciences.

“However, the new fossil, found in amber from northern Myanmar, is exceptionally well preserved, even the luminous organ in its abdomen is intact.

“Elateroidea is one of the most heterogeneous groups of beetles and it has always been very difficult for entomologists to manage, especially because important anatomical innovations have evolved several times independently in independent groups,” said Dr Erik Tihelka, researcher at the School of Earth Sciences at the University of Bristol.

“The discovery of a new extinct elateroid beetle family is important because it sheds light on the evolution of these fascinating beetles.

General habit of Cretophengodidae and closely related representatives of Phengodidae and Rhagophthalmidae, under incident light: (a, b) Cretophengodes azari, dorsal and ventral views, respectively, with an arrowhead showing the photic organ;  (c, d) Zarhipis sp.  (Phengodidae), dorsal and ventral views, respectively;  (e, f) Rhagophthalmus sp.  (Rhagophthalmidae), dorsal and ventral views, respectively.  Scale bars - 2mm in (a, b, e, f) and 4mm in (c, d).  Image credit: Li et al., Doi: 10.1098 / rspb.2020.2730.

General habit of Cretophengodidae and closely related representatives of Phengodidae and Rhagophthalmidae, under incident light: (a, b) Azari cretophengodes, dorsal and ventral views, respectively, with an arrowhead showing the photic organ; (c, d) Zarhipis sp. (Phengodidae), dorsal and ventral views, respectively; (e, f) Rhagophthalmus sp. (Rhagophthalmidae), dorsal and ventral views, respectively. Scale bars – 2mm in (a, b, e, f) and 4mm in (c, d). Image Credit: Li et al., doi: 10.1098 / rspb.2020.2730.

A specimen of Burmese amber with Azari cretophengodes came from amber mines near Noije Bum hill in Kachin State in Myanmar.

The ancient beetle was so unique that researchers created a new family, Cretophengodidae, for it.

“The unique combination of characters in Azari cretophengodes is unknown in any currently defined beetle line, ”they said.

“Therefore, Azari cretophengodes deserves family status in Elateroidea. “

Azari cretophengodes also depicts a transitional fossil connecting the elateroid beetles with soft and hard bodies.

“The newly discovered fossil, preserved with living fidelity in amber, represents a missing relative of fireflies and the living families Rhagophthalmidae and Phengodidae,” said Dr Yan-Da Li, a researcher at Peking University and the Nanjing Institute of Geology and Paleontology and Center of Excellence in Life and Paleoenvironment of the Chinese Academy of Sciences.

“We believe that light production first evolved in the soft and vulnerable larvae of the beetle as a defensive mechanism to ward off predators.

“The fossil shows that during the Cretaceous period light production was also absorbed by adults,” said Dr Robin Kundrata, a researcher in the Department of Zoology at Palacký University.

“He could have been co-opted to perform other functions such as locating partners.”

The results were published in the Proceedings of the Royal Society B.

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Yan-Da Li et al. 2021. Cretophengodidae, a new family of Cretaceous beetles, sheds light on the evolution of bioluminescence. Proc. R. Soc. B 288 (1943): 20202730; doi: 10.1098 / rspb.2020.2730

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