Found in a piece of middle chalk stone from northern Myanmar, the wonderfully preserved male of Cretophengodes azari has a light organ on the abdomen that presumably served a defensive function.
An artistic reconstruction of Cretophengodes azari; the larviform female in the background is reconstructed based on the existing Phengodidae and Rhagophthalmidae beetles. Image Credit: Li et al., doi: 10.1098 / rspb.2020.2730.
Bioluminescence, the production of light by living organisms, has evolved 30 times independently on diverse branches of the tree of life, including algae, livestock, fish, and sea worms.
On land, light-producing beetles are the most widespread and abundant bioluminescent organisms. Their extensive flash exhibits play a role in recognizing size as well as in signaling, communicating and attracting prey.
The majority of these beetles – more than 2300 species – belong to the superfamily Elateroidea (fireflies, fire beetles, glowworms).
The evolution of bioluminescence in these beetles is associated with unusual morphological changes, such as soft body and neoteny (slowing or slowing down physiological development), but the fragmentary nature of their fossil record reveals little about the origin of these adaptations.
“Most light-producing beetles are soft and fairly small, and also have a rare fossil record,” 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, said. and the Center for Excellence in Life and Pale Environment of the Chinese Academy of Sciences.
“However, the new fossil, found in amber from northern Myanmar, is exceptionally well preserved, even the light 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 deal with, especially since important anatomical innovations have often developed independently in unrelated groups,” said Dr. Erik Tihelka, a researcher from the School of Earth Sciences at the University of Bristol.
“The discovery of a new extinct breeding family is important because it helps to shed the evolution of these fascinating beetles.”
Common habitat of Cretophengodidae and representatives of the closely related Phengodidae and Rhagophthalmidae, under incident light: (a, b) Cretophengodes azaridorsal and ventral views, respectively, with 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 – 2 mm in (a, b, e, f) and 4 mm in (c, d). Image Credit: Li et al., doi: 10.1098 / rspb.2020.2730.
A copy of Burmese amber with Cretophengodes azari derived from amber mines near Noije Bum Hill in Kachin State in Myanmar.
The ancient beetle was so unique that the researchers created a new family, Cretophengodidae, for it.
‘The unique combination of characters in Cretophengodes azari is unknown in a currently defined beetle line, ”they said.
“Therefore, Cretophengodes azari earns family status in Elateroidea. ”
Cretophengodes azari also represents a transitional fossil that connects soft and hard body beetles.
“The newly discovered fossil, preserved with fidelity in amber, represents an extinct relative of the fireflies and the living families Rhagophthalmidae and Phengodidae,” said dr. Yan-Da Li, a researcher at the University of Beijing and the Nanjing Institute of Geology and Paleontology and the Center for Excellence in Life and Pale Environment of the Chinese Academy of Sciences.
“We think light production initially evolved into soft and vulnerable beetle larvae as a defense mechanism to repel predators.”
“The fossil shows that during the Cretaceous, light production was also absorbed by adults,” said Dr. Robin Kundrata, a researcher in the Department of Zoology at Palacký University, said.
“It would possibly be co-opted to serve other functions such as tracking buddies.”
The findings are in the Proceedings of the Royal Society B.
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Yan-Da Li et al. 2021. Cretophengodidae, a new Cretaceous family, sheds light on the evolution of bioluminescence. Proc. R. Soc. B 288 (1943): 20202730; doi: 10.1098 / rspb.2020.2730