World’s first case of parthenogenesis in crocodiles (Source: Pixabay) © ANSA/Ansa
First case of a female crocodile succeeding in laying eggs without mating with a male, one of which contained a fetus genetically almost identical to the mother. The discovery, published in Biology Letters by a group of American researchers, raises the possibility that this unusual reproductive modality could even date back to the time of the dinosaurs.
Reproduction without fertilization (parthenogenesis) has been documented in more than 80 species of vertebrates, including snakes, sharks and lizards, but has never been observed in crocodiles. What left researchers speechless was an 18-year-old female Crocodylus acutus kept at a reptile park in Costa Rica. After 16 years in captivity, without ever having met a male, she managed to lay 14 eggs, seven of which appeared to be fertile, were laid in the incubator. After waiting three months, hatching did not occur and the eggs were analyzed to check their contents. One contained a complete but non-viable fetus.
Genetic analyzes showed that it was a female whose DNA was 99.9% identical to the mother’s DNA. In practice, in the absence of a male to mate with, the female crocodile would have fused two of its cells: an egg cell (which contained half of its chromosomes) and another type of cell endowed with a bisected chromosome assembly (this is the case ). the so-called “polar body”, a small cellular structure expelled from an ovum consisting of nuclear material and a small amount of cytoplasm). The merging of the two cells would have required even a minimal reorganization of the genetic material to fill the gaps created by the absence of the male genome: this would have resulted in the creation of an individual that was almost a clone of the mother.
With parthenogenesis documented in both crocodiles and birds, one can speculate that their common ancestor, the dinosaurs, may have possessed similar reproductive abilities.
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