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In fact, it is the oldest fossil in which sperm are uniquely identified. Additionally, this example represents a previously unknown species of crustacean that was named Myanmarcypris hui. M. hui were shellfish, as evidenced by a pair of lime valves that form a carapax, resembling a shell of bivalve mollusks.
“This find provides us with an extremely rare opportunity to learn more about the evolution of these organs,” says Renate Matzke-Karasz, a geobiologist at the Ludwig-Maximilians University (LMU) in Munich, who played a key role in the morphological analysis of fossils. .
During the Cretaceous, mollusks lived in coastal and inland inland waters, dominated by trees that excreted many resins. These just described examples are among the many organisms trapped in the clans of this adhesive.
In recent years, amber found in Kachin province has provided impressive fossil treasures, including frogs and snakes, as well as parts of dinosaurs believed to be (according to new evidence, this specimen belonged to an unusual lizard). During the last 5 years, hundreds of unknown species based on such inclusions have been described. In fact, many of them have forced evolutionary biologists to reconsider the hypotheses of conventional phylogenetic and ecological relationships.
New shellfish samples were analyzed using 3D computer X-ray reconstructions. These images have revealed amazing details of the anatomy of these animals, from small limbs to reproductive organs. And in a female sample, Matzke-Karasz and his colleagues discovered mature sperm. These cells were discovered in paired sperm traps where they are kept after copulation to be released when the female’s eggs mature.
“This female was supposed to be in the resin shortly after mating,” says He Wang of the Chinese Academy of Sciences in Nanjing. X-rays also show sperm pumps and a pair of penises inserted by male shellfish into female double gonopores.
Discoveries in Burmese amber provide an unparalleled opportunity to observe unexpectedly ancient and advanced cases of evolutionary specialization. “The complexity of the reproductive system of these species raises the question whether such investment in giant sperm is an evolutionarily stable strategy,” says Matzke-Karasz.
In most animal species, males (including humans) secrete large numbers of very small sperm. Relatively few animals, including some species of fruit flies and, of course, shellfish, have taken a different approach. They secrete a small number of large sperm, the movable rods of which are several times longer than the animal itself.
“To show that the use of giant sperm is not simply an outlandish turn of evolution, but a strategy that provides an advantage that allows the species to survive for a long time, we must determine when such a mode of reproduction occurred,” says Matzke-Karasz .
Fossilized semen is extremely rare. Before the new discovery, the oldest sperm were 17 million years old, and the previous record age, 50 million years, belonged to the worm species. The new findings are at least twice this age.
The fact that giant sperm in animals were already developed 100 million years ago suggests that this reproductive strategy may be successful for a (very) long time, Matzke-Karasz notes. “It’s a really impressive record for a trait that requires a lot of effort from both men and women. So, evolutionarily, sexual reproduction with such giant sperm must be a truly successful strategy. “
Prepared by the Ludwig Maximilian University of Munich, scitechdaily.com
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