Scientists have discovered a 100 million year old amber that contains the oldest animal sperm sample in history, each of which is surprisingly long. More impressively, a sperm (larger than human sperm) belonged to a crustacean smaller than a sesame seed.
The amber piece contains ancient crustaceans.
Only 0.6 millimeters long, this ancient bivalve is part of a tiny crustacean called Ostracod, known for possessing sperm larger than itself. It sounds ridiculous, but when the microscopic cells curl, tangle together into a small cell, the sperm can easily enter the female body and block the sperm trying to conceive. other.
The researchers used microscopic CT scanners and found 39 ancient crustaceans fit in a piece of amber. Even more surprisingly, these individuals still had fertility traits like today’s Ostracod class, which included giant sperm, mating lobes, and sperm pumps. In particular, scientists also discovered sperm in the female body.
“The fact that the female’s sperm receptor is in a state of enlargement due to the fact that she has received a large amount of spermatozoa indicates that mating takes place not long before the animal is trapped in amber“, The researchers wrote in the report.
Although measuring single cells is impossible, scientists can still make the judgment about sperm size: they are at least 0.2 mm long, which is a quarter of the size of the human body. object.
It is also the oldest animal sperm sample ever discovered. There have been fossils dating back longer, carrying evidence of large genitals, but science has never had any sperm samples.
Ancient sperm in the female.
In 2014, archaeologists discovered fossils of Ostracod-class animals dating back 16 million years, among them were sperm samples up to 1.2 mm long. But this newly discovered fossil in Myanmar is “older” to 83 million years.
Over such a long period of time, the reproductive morphology of the Ostracod class did not seem to have changed much. As the study authors put it, they are “Great example of evolutionary stasis“.
Most likely, while the Ostracod mating, they use their fifth limb to grip the female. Once they are in place, they use a tube to deliver their immobile sperm into the female. Scientists assume that once the sperm reaches its reservoir, they will proceed to rearrange the tangled body to begin fertilization.
Miraculously, the smallest creatures that produce the largest sperm in the animal kingdom. Scientists think that when the female can mate with other males, having large sperm will help to maintain a higher race. However, large spermatozoa also has certain disadvantages.
First, the “tools” for creating, transmitting and receiving sperm would have to be larger. When the organism is inherently small, having large sex organs will limit the area to develop of other organs. Science is not sure why there are creatures with these strange features and where the “giant genitals” appear, research is difficult when direct evidence rarely appears. Crustacean fossils abound, but soft tissue is rare to find.
That is yet another reason why the new discovery is special: not only is the amber preserving soft tissue from many organisms that lived hundreds of millions of years ago, but also evidence of similarities between Ancient and modern crustaceans.
“In the fossil sample of the Ostracod layer, the lobule, pump sperm, semen penis of the male and the sperm receiving area of the female, filled with giant sperm, have not changed for 100 million years.“, The authors conclude.