Jurassic insect carried eggs on its legs, fossils show

Insects that lived 160 million years ago carried clusters of eggs that hung from their legs like grapes hanging from vines. Scientists recently discovered evidence of this parenting behavior in remarkably well-preserved fossils that may be the first example of brood care – in which a parent protects its eggs or young offspring by carrying them – in a species of insect. .

The researchers excavated the insect fossils from the Haifanggou Formation, a fossil-filled rock deposit near the village of Daohugou in northeast China. A wide variety of fossils have been recovered from the site in the past, including the preserved remains of feathered dinosaurs, ancient mammals, giant fleas and long-horned scorpionflies.

In a study published Wednesday, July 13 in the journal Proceedings of the Royal Society B: Biological Sciences (opens in a new tab)the researchers analyzed nearly 160 fossils Karataviella popovi, an extinct species of water bug with oar-like hind legs. The fossils – which the study’s authors called “exceptional” – are 163.5 million years old, meaning they date to the mid-Jurassic period (201.3 million to 145 .5 million years).

Among these fossils, the team identified 30 adult female specimens with a cluster of eggs anchored to their left “mesotibia”, the middle leg of their left leg trio. The densely packed eggs were arranged in five or six staggered rows, with six to seven eggs per row, each attached by a short “egg stalk”. Each egg measures approximately 0.04 to 0.05 inches (1.14 to 1.20 millimeters) in diameter – quite a hefty size considering that K.popovi adults are only about 0.5 inches (12.7 mm) long.

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example of a fossilized Karataviella popovi specimen with eggs on its leg

A group of eggs can be seen on one of the extended legs of this Karataviella popovi specimen. (Image credit: Courtesy of Diying Huang)

K.popovi the females likely laid the eggs directly on their legs by first secreting a sticky mucus and then performing “specific abdominal flexion movements” to expel the eggs onto the appropriate limb, the authors hypothesized. of the study. “The unoccupied right midtibia could have been used to maintain balance when swimming and feeding,” they wrote in their report.

The water bugs’ massive eggs likely contained plenty of nutrients for their offspring – but laying large eggs also comes at a cost, the authors noted. Large eggs are more difficult to aerate with oxygen than small eggs, due to their low surface area to volume ratio. It may be that by carrying eggs on their legs and letting the eggs jiggle gently on their stalks, K.popovi maximized the flow of oxygen from the surrounding water to their developing offspring.

“To our knowledge, carrying a cluster of eggs on [one] The leg is a unique strategy among insects, but is not unusual among aquatic arthropods,” that is, crustaceans, the study authors wrote. the evolutionary and adaptive importance of brood care in insects.”

Originally posted on Live Science.