Amber is the perfect time capsule. In the golden gloop are ancient life-forms transported from eternity to the present day. They are preserved in incredible detail in all of their bizarreness and glory.
Although the ethical issues surrounding Burmese amber mining and sale are complex, amber deposits found in Myanmar still represent a treasure trove of scientific discoveries, showing how diverse life was almost 100 years ago.
Scientists report that sometimes what they look like can be quite the opposite of what we expect. This is what a new study shows. It documents "extreme morphologies in fossilized larvae" of ancient Neuroptera lacewings.
Along with other Neuropterans, Lacewings are part of the superorder Holometabola (aka Endopterygota). In this superorder, the insect goes through holometabolism, a complete metamorphosis. The insect's body develops and transitions from one life stage to another.
"The niche differentiation between the larva and adult of Holometabola is responsible for the enormous evolutionary and ecological success of Holometabola," says Joachim Haug, a paleobiologist from Ludwig Maximilian University of Munich.
(Haug et al., Scientific Reports, 2021)
Above: Cretaceous Lacewing Larvae have elongated stylets and appendages.
There is a common belief among biological circles that larvae of holometabolans, the immature forms, of insects, are worm-like creatures. They have not had the chance to develop pronounced features like eyes, antennae and mouthparts.
Researchers write that "holometabolan larvae may be something like early-hatched embryos and thus possess a type of morphology that is 'not yet ready'."
"All of these ideas indirectly suggest that holometabolan larvae are constrained in their ability to evolve morphologically varied forms."
This line of thinking is challenged by some very old lacewing larvae that were trapped in time during the late Cretaceous (about 100million years ago). It could be us, not the lacewings' protruding, who are being constrained in our thinking.
Haug and his colleagues discovered many lacewing larvae specimens in amber deposits from the Hukawng Valley of Myanmar. They had a variety elongated antennae and jawbones.
Particularly, the lacewing larvae that were studied showed straight venom-injecting and piercing sucking mouthparts. These protruded from the jaw and are known as a "stylet".
(Haug et al., Scientific Reports, 2021)
Above: Cretaceous Lacewing Larvae have elongated stylets and appendages.
Haug suggests that the long stylet could have been used to keep their wounded victims away from the toxin until it began to take effect. However, the hypothesis is hard to verify 100 million years later.
"As with all modern species, lacewings, these larvae probably preyed on their prey, but we don't know much about them."
Even though we don't know for certain how these body parts functioned in the Cretaceous, enough evidence is available to refute the argument that creatures such as lacewings only get prominent body features when they are adults.
Haug and his colleagues suggest that the "general" pattern of holometabolan larvae is not a reflection of scientific ignorance about larval forms and how complex they can be.
We can see a rare example that this complexity was preserved 100 million years ago.
This evolutionary loss could help us understand the immature holometabolans better, but it doesn't mean that we should undervalue them. Evidence of absence is not evidence of absence.
Scientists explain that there is no major constraint that prevents holometabolan larvae from developing such structures.
"[The examples here] again demonstrate that if you only consider modern-day fauna, it will give the impression that there are certain morphological and developmental constraints, but these are actually artifacts of 'filtering his history.
These findings are published in Scientific Reports.
