Bursting into life

By Ricardo Pérez-de la Fuente, Museum Research Fellow

One of the earliest and toughest trials that all organisms face is birth. In egg-laying animals, the egg shell that has protected the embryo during its early development ultimately becomes a hard barrier between the animal and its life out in the world. The bursting of the egg is literally a threshold moment, and there are many ways to crack an egg…

Some animals break the egg membranes using dissolving chemicals; others physically, mechanically tear their way through the shells. Among the latter, a great diversity of animals use specialised devices called egg bursters. These vary greatly among the many arthropods and vertebrates that use them, but perhaps the most famous example is the ‘egg tooth’ that is present on the beak of newborn chicks.

Four complete Tragychrysa ovoruptora newborns preserved together with egg shell remains and one egg burster. Modified from the open access Palaeontology paper.

My colleagues and I have found an exceptional fossil in 130 million-year-old Lebanese amber. Inside, trapped together are newborn larvae from Green Lacewings, the split egg shells from where they hatched, and the minute egg bursters that the hatchlings used to crack the egg. This is a first: no definitive evidence of these specialised egg-bursting structures had been reported from the fossil record of any egg-laying animals, until now.

The finding has been recently published as open access in the journal Palaeontology. Because multiple newborns were ensnared and entombed in the resin simultaneously, the fossil larvae have been described as the new species Tragichrysa ovoruptora, meaning ‘tragic green lacewing’ and ‘egg breaking’. A sad event, indeed, taking place in an ordinary day 130 million years ago in the Cretaceous forests of Lebanon, yet a happy circumstance now that we can take a privileged glimpse into the adaptations and behaviours of these fascinating tiny creatures.

The hatchlings from modern Green Lacewings open a slit on the egg with a ‘mask’ bearing a saw-like blade. Once used, this ‘mask’ is shed together with the embryonic cuticle and is left attached to the empty egg shell.

With the help of Amoret Spooner, Collections Manager at the Museum, egg clutches from modern green lacewings were found in the Museum collections. These eggs happened to have the intact egg bursters still attached to them, and proved to be crucial to understand that we had the same structures preserved in the amber together with the newborn larvae.

Two Tragychrysa ovoruptora newborns preserved together with egg shell remains and two visible egg bursters (right inset). Modified from the open access Palaeontology paper.

Green Lacewing larvae are small predators that often carry debris as camouflage, using their sickle-shaped jaws to pierce and suck the fluids of their prey. Whereas the larvae trapped in amber differ significantly from modern-day relatives, in that they possess long tubes instead of clubs or bumps for holding debris, the studied egg shells and egg bursters are remarkably similar to those of today’s green lacewings.

The larvae were almost certainly trapped by resin while clutching the eggs from which they had freshly emerged. Such behaviour is common among modern relatives while their body hardens and their predatory jaws become functional. Indeed, the two mouthparts forming the jaws are not assembled in most of the fossil larvae, which indicates, together with the large relative size of the head and legs, that they were recently born.

Detail of a head with the jaws still dislodged, indicating that the larva was recently hatched when it was ensnared by amber and the jaws had not yet had time to fully assemble.

It may seem reasonable to assume that traits controlling a life event as decisive as hatching would have remained largely unchanged during evolution. In fact, we see in very closely related insect groups different means of hatching that can entail the loss of the egg bursters. So the persistence of a hatching mechanism in a given animal lineage through deep time can’t be determined without direct proof from the fossil record.

Reconstruction of two Tragichrysa ovoruptora newborns clutching the eggs from where they recently hatched, moments before they were trapped by resin. Larvae colour and egg stalks are conjectural. Extracted from the open access Palaeontology paper.

This new discovery shows that the mechanism green lacewings use to crack the egg was already established 130 million years ago. Overall, it represents the first direct evidence of how insects hatched in deep time, egg-bursting their way through into life.

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The hatching mechanism of 130-million-year-old insects: an association of neonates, egg shells and egg bursters in Lebanese amber by Ricardo Pérez-de la Fuente, Michael S. Engel, Dany Azar and Enrique Peñalver is published as open access in Palaeontology this month.

Crafty camouflage

Last week we brought you snails that attach all manner of pebbles, fossils, corals and shark teeth to their shells. Today we give you a newly-discovered fossil green lacewing larva that attached pieces of soil to its body as an act of camouflage. Our research fellow Ricardo Pérez-de la Fuente, lead author of the new paper, explains…

Visual camouflage is one of the most successful survival strategies in nature. Camouflaging is usually defensive, allowing animals to be left unnoticed by their predators, but it can also be used aggressively by predators themselves to approach their prey undetected.

Some camouflaging animals can actively change their colouring to match that of the background ‒ a technique called crypsis. Others can make their bodies resemble elements of the environment, such as leaves or twigs, which is called mimicry.

Italochrysa italica, an extant green lacewing larva carrying a dense debris packet made of soil fragments. Taken from the open access publication Tauber & Winterton, 2014.

Yet another approach to camouflage involves collecting diverse materials from the environment and incorporating them on the animals’ bodies in order to better blend with the surroundings. This is known as debris-carrying, trash-carrying, or decoration, and it can be found across a wide variety of animals including sea urchins, gastropods, and arthropods, such as decorating crabs, or sand- and mud-covering spiders.

My colleagues and I have just published the discovery of a fossil green lacewing larva, pictured at the top of the article, that has been preserved carrying bits of soil that it used for camouflage and physical protection. It’s a new larval species just 1.5 mm in length, and is preserved in Early Cretaceous Lebanese amber. We have named it Tyruschrysa melqart after the Phoenician city of Tyre and its tutelary god Milk-Qart (if you want to learn the reasons behind this name check out our open access paper!).

Interpretative drawing of Tyruschrysa melqart: body in grey, ‘tubes’ with setae coloured according to which body part they are attached to, and soil debris in brown.

Green lacewing larvae are active predators that eat other insects such as aphids, using sickle-shaped ‘jaws’ to pierce their prey, suck out their fluids and liquefy their tissues; eating is easier when there is no need to chew! Some green lacewing larvae are debris carriers, entangling all kinds of debris among their velcro-like ‘hairs’ called setae, which extend from relatively short ‘bumps’ on their backs. This debris is carefully selected and gathered with meticulous head and body movements to form a so-called debris packet on the back of the insect.

‘Tubes’ bearing setae of Tyruschrysa melqart, with detail of their mushroom-shaped endings (bottom), used for anchoring bits of soil.

The new fossil and similar ones described from younger Cretaceous ambers differ from modern relatives because instead of short ‘bumps’ with setae on their backs they have relatively long ‘tubes’, giving them a bizarre appearance.

These tubes have setae with mushroom-shaped endings of a kind never seen before in extinct or living green lacewing larva species. The mushroom-shaped ending is a special adaptation to anchor debris, which in the case of Tyruschrysa melqart are fragments of soil.

Hallucinochrysa diogenesi, another Cretaceous green lacewing larva bearing long ‘tubes’ with setae on its back, but carrying a debris packet made of plant hairs (trichomes). Preserved in Spanish amber (105 million years old).

It was already known that Cretaceous green lacewing larvae like Tyruschrysa had long tubes on their backs and that they collected plant hairs and other plant material to construct their packet of debris. But thanks to the new discovery we now know that these immature insects also used bits of soil, and that in the deep past debris packets were probably as diverse as those we see today.

Green lacewing larvae have been gathering debris to camouflage and protect themselves for about 130 million years, giving rise to the different body adaptations we see amongst these fascinating tiny collectors.

‘A soil-carrying lacewing larva in Early Cretaceous Lebanese amber’ Ricardo Pérez-de la Fuente, Enrique Peñalver, Dany Azar and Michael S. Engel is published as open access in Scientific Reports this month.