World’s oldest sperm is discovered inside a female crustacean that mated and was then trapped in amber 100 million years ago
- The ‘spectacular find’ is inside an ostracod, a tiny mussel-like marine creature
- Experts said that the ostracod belongs to a new species, ‘Myanmarcypris hui’
- It would have lived in the coastal and inland waters of what is today Myanmar
- The discovery is shining light of the evolution of reproduction and giant sperm
The earliest known sample of sperm has been discovered inside a female crustacean that was preserved in amber shortly after mating some 100 million years ago.
Dubbed a ‘spectacular find’, the specimen from Myanmar’s Hukawng Valley is an ostracod — a type of microscopic crustacean that resembles a mussel.
In fact, the specimen belongs to a previously-unknown species, which the researchers have named Myanmarcypris hui.
M. hui would have lived along the coasts and inland waters of prehistoric Myanmar, surrounded by trees that produced huge quantities of the resin that forms amber.
The discovery provides ‘an extremely rare opportunity’ to learn more about the evolution of the reproductive process in animals, the researchers said.
Before now, the oldest-known fossilised animal sperm was thought to have been found in a 50-million-year-old worm cocoon recovered from Antarctica.
The earliest known sample of sperm, pictured, has been discovered inside a female crustacean that was preserved in amber shortly after mating some 100 million years ago
In their study, geobiologist Renate Matzke-Karasz of the Ludwig-Maximilians-Universitaet in Munich and colleagues analysed 39 specimens of ostracods that had been trapped in a tiny piece of amber — using X-ray scans to reconstruct them in 3D.
The researchers identified ripe giant sperm stored in a pair of sperm receptacles inside the female ostracod — kept waiting ready for her eggs to mature, in what could also be the earliest direct evidence of a completed insemination.
While the majority of the male members of animal species — humans included — produce large quantities of very small sperm as to increase the chance of fertilisation, there are exceptions.
Some creatures — such as fruit flies and modern-day ostracods — produce a small number of oversized sperm, each of which sport tails several times longer than the actual animal itself.
In these cases, chances of fertilising an ovum can increase with the size of the sperm cell, the researchers explained.
Knowing more about how giant sperm cells evolved could shed light on what the researchers describe as an ‘ancient and advanced instance of evolutionary specialisation’.
In their study, geobiologist Renate Matzke-Karasz of the Ludwig-Maximilians-Universitaet in Munich and colleagues analysed 39 specimens of ostracods that had been trapped in a tiny piece of amber — using X-ray scans to reconstruct them in 3D, as pictured
Myanmarcypris hui — two of which are pictured here mating in this artist’s impression — would have lived along the coasts and inland waters of prehistoric Myanmar, surrounded by trees that produced huge quantities of the resin that forms amber
‘The most significant part of our story is that we can now show that using giant sperm for reproduction is something that can last long in Earth history,’ Dr Matzke-Karasz told the PA news agency.
‘Previously, we were not sure if animals that ‘switched’ to using these giant sperm at a certain point in their evolutionary history [were] doomed to become extinct very quickly,’ she explained.
‘After all, these are enormous costs for the animals — large sperm must be produced, the reproductive organs are much bigger than in other species, they take up a lot of space in the animal and mating lasts long.’
‘This is a lot of biological energy that must be allocated to reproduction — so you might think that this doesn’t make sense from an evolutionary standpoint.’
‘But in ostracods, it seemed to work for more than 100 million years,’ she added.
‘From an evolutionary point of view, sexual reproduction with the aid of giant sperm must, therefore, be a thoroughly profitable strategy.’
The full findings of the study were published in the journal Proceedings of the Royal Society B.
FOSSILS IN BURMESE AMBER
Amber, often used in jewellery, is fossilised tree resin, and the oldest dates back more than 300 million years.
In the past few years the Hukawng Valley in northern Myanmar, formerly Burma, has yielded numerous finds.
In January 2017, researchers discovered a 100-million-year-old insect preserved in amber which bore a passing resemblance to ET.
Its features were so odd and unique that researchers placed in into a new scientific order of insects.
The creature had a triangular head and bulging eyes, which is different from any other known species of insect.
The eyes on the side of its head would have given it the ability to see at almost 180 degrees by simply turning its head to the side.
Because of its uniqueness, the insect was assigned its own brand new scientific classification order – called Aethiocarenodea.
In June 2017, researchers revealed a stunning hatchling trapped in amber, which they believe was just a few days old when it fell into a pool of sap oozing from a conifer tree in Myanmar.
The incredible find showed the head, neck, wing, tail and feet of a now extinct bird which lived at the time of the dinosaurs, 100 million years ago, in unprecedented detail.
Researchers nicknamed the young enantiornithine ‘Belone’, after a Burmese name for the amber-hued Oriental skylark.
The hatchling belonged to a group of birds known as the ‘opposite birds’ that lived alongside the ancestors of modern bird.
Archaeologists say they were actually more diverse and successful – until they died out with the dinosaurs 66 million years ago.
They had major differences from today’s birds, and their shoulders and feet had grown quite differently to those of modern birds.
In December 2017, experts discovered incredible ancient fossils of a tick grasping a dinosaur feather and another – dubbed ‘Dracula’s terrible tick’ – swollen after gorging on blood.
The first evidence that dinosaurs had bloodsucking parasites living on them was found preserved in 99 million-year-old Burmese amber.
The newly-discovered tick dates from the Cretaceous period of 145 to 66 million years ago.