Intriguing Insect Fossils Protected in Brownish-Yellow Amber
LMU Zoologists Have Uncovered Examples of Ancient Amber– Insect Larvae with Unusual Morphologies and Larvae of Early Flying Insects
Every fossil is a time capsule. However, unlike numerous other finds, insects encapsulated in amber are often flawlessly preserved. According to Professor Joachim T. Haug, LMU zoologist, often, their exterior morphology is well preserved as if they had been sealed in synthetic resin.
Now, he and his colleagues have acquired new insights into the evolutionary history of insects from specimens caught in natural tree resins 100 million years ago in forests in what is now Myanmar.
Amongst the finds are fossil lacewing larvae whose morphology differs noticeably from that of the ‘typical’ insect larva. Their most distinctive attributes are their elongated appendages– specifically, the mouthparts called stylets, which resemble hypodermic needles.
“As in the case of all modern-day species of lacewings, these larvae were most likely predators. However, we know absolutely nothing about their prey,” says Haug. Modern species eat aphids, immobilizing them by injecting them with venom, feeding on their contents. Nevertheless, the cuticle of aphids is so soft that much smaller-sized sucking appendages would suffice to permeate them.
Haug suggests that the long stylet may have served as a means of maintaining their wounded victims at a distance up until the toxin began to work. However, since the most extreme examples of extended appendages were discovered in currently extinct species. He and his colleagues assume that this body configuration may have proven to be an evolutionary stalemate.
The fossil larvae shed light on ecology and developmental biology
Since that lacewings are currently relatively rare, the degree of species richness of the lacewing group discovered amongst the amber-encased fossils from Myanmar suggests that the group was more diverse in the Cretaceous Period.
In turn, this indicates that these insects played a much more conspicuous ecological part back then. “They were perhaps an essential constituent of the food cycle, considering that they successfully changed virtually inedible materials into nutritious food for birds,” claims Haug.
The fossils likewise clarified another element of insect evolution. Previously, it has been assumed that the relative length of structures such as antennae, sensory organs, and legs undergo developmental constraints. In most insect larvae, these body structures are generally significantly shorter than in the fully grown adult, and– generally speaking– the larva is a more worm-like form of life.
However, many of the lacewing larvae found in amber, antennae, mouthparts, and legs tend to be noticeably elongated. “This demonstrates that, from the perspective of developmental biology, there are no strictly defined restrictions to the lengths of such structures,” Haug mentions.
The nature of the environment
However, one other facet of insect evolution continues to puzzle developmental biologists. Did the first insects capable of flight spend their larval lives on land or in the water? Joachim Haug and his group discovered a hint to the solution in 99-million-year-old brownish-yellow from Myanmar– a specimen of the fossil dragonfly varieties Arcanodraco filicauda.
They analyze the morphology of this discovery as showing that the earliest flying insects spent the preliminary stages of their life cycle in water. Additional evidence supports this idea.
Dragonflies, mayflies, and stoneflies represent ancient family trees of flying insects– and their modern descendants invest the larval stage (which can last for several years) in water before they undertake metamorphosis and take to the air as– short-lived– adults.
“It looks as if the earliest flying bugs were extremely depending on an aquatic environment for recreation,” says Haug. Probably the first successful take-off from the surface area of a fish pond was accomplished with the help of wings that worked as sails.
Read the original article on Sciencedaily.
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