Under the frozen soil of Antarctica, an international team of researchers from the paleobiology department of the Swedish Museum of Natural History, the University of Milan (Italy) and the Argentine Antarctic Institute have discovered an unusual prehistoric gem : the oldest sample of sperm of animals ever found. The finding has been published in the journal Biology Letters.
This fossil sperm unearthed in Antarctica is 50 million years old and belongs to a variety of worms, the clitelate annelids ( Clitellata ), better known as leeches, earthworms and derivatives.
The scientists, using the scanning electron microscopy technique , discovered inside a piece of only 1.5 millimeters of a broken cocoon, remains of different parts of the typical clitelate spermatozoa. a “network of intertwined cables” located within the wall of a worm cocoon, later revealed to be a surprisingly exquisitely preserved sample of clitoral annelid sperm .
Their examination has determined that these prehistoric sperm are very similar to the current ones, coming from the also Branquiobellid invertebrates that usually live as parasites of crayfish. The revelation of this similarity is at the moment a mystery and a surprise with respect to how these leeches evolved since it would suppose a true evolutionary revolution with respect to what we know so far, basically because the sperm has been discovered in the southern hemisphere, in the Antarctica, and this type of worms is characteristic of the fresh waters of the planet’s northern hemisphere.
Until now, the oldest sperm in the animal world was 40 million years old and came from a springtail ( Collembola ) that was discovered in a fossil state in a piece of amber.
