Tag: Spain

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A GUT FULL OF SAND

UNEARTHING THE PECULIAR EATING HABITS OF A TRIASSIC MAYFLY SPECIES

During the summer months, the beaches of Mallorca offer an irresistible draw for tourists and palaeontologists alike. Visitors to the small Spanish island find themselves lured by its glittering seas, captivating coastline, and tasty white sands…

…well, tasty for some, at least!

Coastal cliffs near Estellencs (Mallorca, Spain). Palaeontologists working here discovered fossils of Triassic mayfly nymphs with unusual gut contents. (photo: Balearic Museum of Natural Sciences)

Following recent fossil excavations near the the coastal town of Estellencs in southwest Mallorca, palaeontologists have discovered evidence of a species of mayfly with a pretty peculiar diet. The mayflies in question lived 240 million years ago in bodies of water associated with ancient floodplains. Some of the juvenile mayflies (nymphs) were so well-fossilised that it has been possible to study the contents of their guts. A research team, led by Dr Enrique Peñalver, and featuring OUMNH’s own Dr Ricardo Pérez-de la Fuente, discovered that the mayflies’ digestive tracts contained a mixture of detritus (the decomposed remains of other organisms) and particles of a type of rock known as claystone. The most likely explanation for this strange food-pairing? It seems that the nymphs actually survived by eating muddy sediments that had settled to the bottom of the swampy-waters they lived in – yum!

If you’ve ever tried eating a sandwich on the beach, you’ll be familiar with the feeling of sand in your teeth. The sharp crunch of mineral sediment is worth the sacrifice for the delicious, digestible portion of your sandwich – the bread and fillings. Animal digestive systems are unable to extract energy from inorganic mineral matter, like sand. Instead, we rely on organic material for nutrition, i.e. matter derived from plants and other animals. It seems that the Triassic mayfly nymphs found in Mallorca would have munched through large quantities of sediment; digesting the organic detritus it contained, and excreting the inorganic remainder.

One of the numerous Early Triassic mayfly nymphs from Mallorca preserved with gut contents. These inclusions result from the original sediment the nymphs fed on (cololite, labelled here with arrows). Image adapted from Peñalver et al. (2023).

Sediment-based diets are extremely rare among living insect species. A handful of modern mayfly species have been observed to munch on the muddy sediment that surrounds the openings of their tunnels, but this is a very rare occurrence. Sediment is a pretty challenging food source, and it’s hard to say why insects may have relied more heavily on it in the ancient past. It is possible that the mayflies found in Mallorca adopted their diet as a result of the Permian mass extinction, which killed off more than 80% of all the species on Earth, ‘just’ five million years prior. With fewer choices of organic material available to eat, perhaps the mayflies were left without a better choice? Or maybe they were simply exploiting new environmental niches that opened up in the aftermath of this catastrophic event?

One of the reasons why it is so difficult to theorise about the evolution of species following the Permian mass extinction is the dearth of fossil evidence dating from the period. Luckily, the coastal cliffs of Mallorca can offer us a rare, exciting glimpse into some of the ecosystems that existed ~247 million years ago. The research team behind the Mallorcan mayfly discovery have also used fossils from the same site to describe the world’s oldest-known dipteran (a group of insects including flies, mosquitoes, gnats, and midges), naming the species Protoanisolarva juarezi. These flies would have lived on land, in back swamp areas, rather than in the water. However, much like the Triassic mayfly nymphs, they would have fed on detritus, and played a key role as recyclers of organic matter in these ancient ecosystems.

The larva of the oldest-known gnat, 247 million years old, was found near Estellencs in Mallorca. (Image: CN-IGME CSIC).

It is by paying attention to tiny insect fossils like these that we might hope to find answers to one of the biggest questions in palaeontology: how did life rebuild in the aftermath of our planet’s worst mass extinction? And what might this teach us about ecosystem responses to future mass extinction events?

By Ella McKelvey, Web Content and Communications Officer

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A grasp of the past

by Ricardo Perez-De-La Fuente, research fellow

Few creatures look weirder – or are cooler, in my opinion – than mantidflies. There are around 400 species of these small predatory insects known worldwide – a scarce diversity by insect standards.

Like praying mantises, mantidflies have long ‘necks’ and forelegs armed with powerful spines and other structures used to hunt their prey with a sudden lethal grasp. The unfortunate victims become immobilised until they are meticulously eaten alive – not the best way to spend your last minutes on Earth!

Mantidflies belong to the Neuroptera order of insects and so aren’t actually related to praying mantises, but to insects such as lacewings and antlions.

A new paper that a colleague and I have published presents a new fossil mantidfly from Spanish amber that is important in understanding the evolution of their gripping – or raptorial – forelegs. The finding is presented in the open access journal Scientific Reports today.

Although the discovery has just been published, we excavated the new fossil during the scorching summer of 2010 in Teruel, northeastern Spain.

Amber excavations are very romantic – while they take place we carefully store the amber, piece by piece, into muddy plastic bags, remaining oblivious of what creatures are being unearthed because the amber surfaces have become opaque during fossilisation. Later, in the laboratory, the surfaces of the amber pieces are polished and screened for inclusions. Then a first glimpse is gained into what has remained frozen in time for millions of years.

It is only when the amber inclusions are carefully examined and studied that the implications of the specimens that were dug up years earlier start to be revealed. In this case, a specimen that was preserved in fragments, nothing spectacular at first look, ended up being truly exceptional.

Foreleg of Aragomantispa lacerata, showing powerful spines and other structures adapted to strike and hold prey.

Extinct true mantidflies, particularly those preserved in amber, are extremely rare. Our new fossil, pictured above at the top of the article, is 105 million years old, from the Cretaceous period. It currently stands as the oldest true mantidfly known in amber. The new extinct species, named Aragomantispa lacerata, has allowed us to compare the structures of the raptorial forelegs between extinct and extant mantidflies with an unprecedented detail.

Comparison between the foreleg spine-like structures of the new fossil mantidfly (up), with those from a close modern species (bottom).

Present-day mantidflies have forelegs with spines that bear minute cones at their tip. These cones are sensory organs that elicit the striking reflex and feel the prey’s movements once captured and restrained by the mantidfly’s tight embrace.

The forelegs of Aragomantispa lack these cones at the spines’ tip, instead having larger, icicle-shaped tips. We do not know how sensitive the mantidfly forelegs were in the Cretaceous, but the spines of at least some of these insects seem to be not as specialised as those from their present-day relatives.

Some mantidflies have smaller, reclined hair-like structures forming an edge on the leg’s surface opposing the spines. These reinforced edges create a scissor effect that stuns prey when the forelegs strike. Although Aragomatispa has these structures on the forelegs, they are also different in shape to those found on extant mantidflies.

Reconstruction of Aragomantispa lacerata striking at a hypothetical prey on a fern in the Cretaceous Spanish forest.

The fossil record offers the only direct means to assess when and how the traits characteristic of a given animal group originated in time. However, this kind of fossil evidence appears very occasionally. Our discovery shows that the foreleg spine-like structures of recent mantidflies were not fully developed in at least some of their Cretaceous ancestors.

The most exciting part is to think that this story and literally thousands more lie waiting to be discovered – or otherwise forgotten forever – buried underground.