Revealing a 100-million-year-old asexual shrimp species

Fossils of fairy shrimp from the Cretaceous period show that this species does not need a male to be able to reproduce normally.

Recently, researchers of freshwater fossils of the Cretaceous period in southern Australia have revealed a new species of extinct freshwater shrimp, the scientific name is Koonwarrella peterorum.

Fossil Koonwarrella peterorum, newly described freshwater shrimp with asexual reproduction

A special feature of this species is that the female is able to reproduce without sperm from the male - also known as asexual reproduction.

Accordingly, the female gives birth to an embryo on her own from an unfertilized egg. This extremely rare mode of reproduction is believed to exist in both plants and animals. Some species, such as the white-tailed lizard (Aspidoscelis uniparens) can even reproduce both asexually and sexually, according to a report in the 2021 Journal of Genetics.

Thomas Hegna, Associate Professor of Paleontology at the State University of New York (SUNY) said that this is the first time that asexual reproduction has been recognized in freshwater shrimp varieties, although there have been some previous studies. Saltwater shrimp varieties have this ability.

The new species was identified from 40 individual fossils at the Koonwarra Geo Reserve, a paleontological site dating from 125 million to 113 million years ago, and numerous fossils, including feathers of dinosaur.

Koonwarrella peterorum's oddities make it look less like modern shrimp, but more closely related to the sea monkey (artemia salina), a type of saltwater shrimp.

According to Hegna, one reason that asexual reproduction is so rare in animals is that the method is not completely optimal, always keeping the genetic code of the first offspring, regardless of whether they are good or bad. Meanwhile, sexual reproduction allows animals to separate good genes from bad ones, thereby directing them to become a more complete species.