LIFE SCIENCE

The Daohugou biota found the earliest insect motherhood


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Ecological restoration map of Kara’s bugs (sun jie)

Not only do insects have maternal love, but the adaptive behavior of insect maternal care dates back at least to the Middle Jurassic. This discovery was proved by the team of Huang Diying, a researcher at the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (hereinafter referred to as the Nanjing Institute of Paleontology), who advanced the direct evidence of insect breeding behavior by nearly 40 million years. On July 13, the results were published online in the Proceedings of the Royal Society B.

In the process of life evolution, parental care is an important adaptive behavior, which refers to the protection, care and feeding of eggs or offspring by both parents, etc., and has evolved independently many times in mammals, birds, reptiles, arthropods, especially social insects. Egg-carrying behavior is a form of parental care, usually the behavior of a single parent carrying eggs or larvae after spawning to provide protection, which can effectively improve hatching rates and offspring survival rates.

However, egg-carrying behavior is difficult to document in insect fossils. Huang Diying, a researcher at the Nanjing Institute of Paleontology, told China Science Daily: “At present, direct fossil evidence of eggs carried by Mesozoic insects has been found only in the Early Cretaceous Rehe biota and Burmese amber in the middle Cretaceous period. ”

In the middle and late Jurassic Daohugou biota, after a systematic study of the representative type of Cara scratch bug, Fu Yanzhe et al. identified 30 female adults carrying eggs in 157 cara scratch bug fossils, and used a variety of technical analysis methods to conduct a functional morphological comprehensive analysis of the cara scratch bug, revealing the unique egg carrying behavior of the middle and late Jurassic scratch bug.

The bugs here are common aquatic hemiptera insects found in freshwater ecosystems around the world. The eggs of the living scratch bugs are often attached through the stem to the leaves and stems of aquatic plants, stones, and even snail shells, turtle shells, and exoskeletons of crayfish. In the Daohugou biota, caraparticula is a larger individual, with a body length of about 11 to 15 mm, a head with 5 clusters of bristles, and a specialized forefoot tarsal node to form a mesh-like predatory device, reflecting a highly specialized predatory behavior.

It is understood that the Harvest Worm and the Cara Bug are both pioneers and representative creatures in the Daohugou biota, and their appearance, radiation, prosperity, decline and demise show a high degree of consistency. Through morphological measurements of more than 700 harvest eggs, the researchers speculated that a large number of seasonal harvest eggs may be a food source for Cala’s bugs.

According to Huang Diying, about 5 to 6 rows of closely arranged eggs with a length of about 6 to 7 1.14 to 1.20 mm in each row can be seen on the left midfoot tibia of some female individuals of Carla scratch bugs, which are attached to the tibia by the egg stalk. Female egg-carrying individuals have a thicker left midfoot tibia than the right midfoot tibia and males.

The researchers speculate that the predatory risks and cyclical food sources caused by the large number of salamanders in the Daohugou biota have exposed the cala crow bugs to great ecological pressure, and the egg-carrying behavior may reflect the adaptation of the cara salamander to the habitat ecological environment or the response to changes in the ancient lake ecosystem.

Huang Diying said: “The egg carrying behavior of Carla Bug can provide physical protection for eggs during the incubation process and effectively prevent egg drying and hypoxia, which is of great significance for its evolution and reproduction. But such acts of selfless maternal protection can come at a higher cost, such as increasing the risk of predation. ”

He also noted that the strategy of egg-bearing has not been found in other living and extinct insect groups, but is not uncommon in aquatic arthropods, whose fossil record dates back to the Early Cambrian Chengjiang biota. However, the behavior of carrying eggs with one side of the foot is an isolated case. The study highlights the diverse and well-known rearing strategies of Mesozoic insects, which helps to understand the evolutionary and adaptive significance of insect juvenile behavior. (Source: China Science Daily Shen Chunlei)

Related paper information:https://doi.org/10.1098/rspb.2022.0447



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