Scientists figure out how a 100-million-year-old shrimp reproduced

(ORDO NEWS) — Shrimp are, in fact, small crustaceans that live in both fresh water and sea water. They reproduce sexually – the female mates with the male, after which caviar develops, from which small shrimp appear. However, scientists have found that shrimp did not always develop in this way.

After examining a 100-million-year-old freshwater shrimp fossil, they concluded that females could do without males. Moreover, this species of shrimp generally consisted only of females.

The method of reproduction they used is called parthenogenesis, that is, one of the types of asexual reproduction. This method of reproduction has been known for a long time, but it is extremely rare in the animal kingdom.

New freshwater shrimp fossil

A new species of extinct freshwater shrimp, dubbed Koonwarrella peterorum, was identified by scientists from forty different fossils found in the Kunwarra seam. It is a paleontological monument that belongs to the Aptian era, that is, the period from 125 to 113 million years ago.

The Kunwarra reservoir is famous for its abundance of various fossils, among which are the feathers of avian dinosaurs, bony fish, and invertebrates, including shrimp, which were only females.

The fossils are held in the paleontological collections of the Melbourne Museum in Victoria, Australia. I must say that shrimp 100 million years old are very different from those that we eat. They are much more reminiscent of modern sea monkeys (Artemia salina), a type of crustacean related to Artemia.

Scientists figure out how a 100 million year old shrimp reproduced 2
Visually, the ancient shrimp looked like brine shrimp

The shrimp left their mark in the 1 centimeter long sediment. The oblong imprint suggests that these crustaceans had elongated bodies with several pairs of legs. Therefore, visually, they resemble a fern leaf, or even a toilet brush.

Scientists figure out how a 100 million year old shrimp reproduced 3
100 million year old shrimp fossil

How fossil shrimp reproduced

Emma Van Hout, a student at New York University SUNY Fredonia, took up the study of a new species of shrimp. She analyzed the fossils to determine their potential place on the evolutionary tree.

However, she had to face a problem – most species of invertebrates are classified according to male morphology. The fact is that a hundred males of most of their species have different characteristics by which scientists distinguish one species from another.

“The males have these big prehensile antennae used for sexual reproduction, as well as male genitalia. But none of the 40 samples Van Hout examined had any of these characteristics,” Van Hout said.

Van Hout clearly identified egg sacs in all the fossils. As a result, I came to the conclusion that this group of shrimp consists exclusively of females.

After other explanations were ruled out, such as hermaphroditism, where an individual has female and male reproductive organs, the only logical explanation was that the fossil shrimp was parthenogenetic.

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Whiptail lizard that reproduces by parthenogenesis

Parthenogenesis – reproduction without fertilization

Parthenogenesis is the development of an embryo from an unfertilized egg. This phenomenon occurs in nature in plants and animals, but is extremely rare.

Whiptail lizards are known to develop in this way. There are also species that reproduce both through parthenogenesis and sexually. These include Californian condors, which we talked about earlier. True, the chicks born of the “immaculate conception” do not live long.

In terms of fossils, Koonwarrella peterorum is the first case of parthenogenesis discovered by scientists. Moreover, for the first time, scientists have discovered parthenogenesis in freshwater.

One reason why asexual reproduction is so rare is that species always pass on their genes, whether good or bad, experts say. With traditional breeding in animals, potentially harmful genes can be “screened out”.

However, parthenogenesis can give shrimp an advantage when it comes to settling in new places, such as small isolated ponds. Finally, let me remind you that last year, scientists investigated another, no less interesting find – a fossil of a giant sea scorpion aged 435 million years.


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