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Coquita the Crocodile, Middle school

A wild American crocodile resting on a riverbank

Coquita the crocodile lived alone at a reptile park in Costa Rica for 16 years. She never met a male. Then she laid 14 eggs.

Could one of those eggs have a baby inside?

Video 1. Virgin birth in a crocodile

Coquita is an American crocodile who lived alone at a reptile park in Costa Rica for 16 years. In 2018 she laid 14 eggs, and one held a fully formed baby with no father’s DNA. Scientists call this parthenogenesis.

Video 2. Coquita’s virgin birth is not a clone

Coquita’s baby got all of its DNA from her, but the baby was not a clone. Her egg ended up with two matching copies of almost every gene instead of one copy from each parent. Where Coquita carried one working copy and one broken copy of a gene, her baby got two of the same.

The Parthenon in Athens
The Parthenon in Athens got its name from Athena Parthenos, “Athena the Virgin.”

Your word of the day is

par-theh-no-JEN-uh-sis

partheno-maiden, virginfrom Greek parthénos
-genesisorigin, birthfrom Greek génesis

An egg develops into a baby without sperm fertilizing the egg.

A drawing of a DNA double helix

Most babies get half their DNA from mom and half from dad. Coquita’s baby got all of its DNA from Coquita.

How was the DNA in Coquita’s baby different from your DNA?

A scientist loading DNA samples into a gel to test them

Some female reptiles can store sperm inside their bodies for years.

How could scientists prove Coquita’s baby didn’t come from old, stored sperm?

An American crocodile at a reptile park

Coquita’s baby was fully formed, but it didn’t survive to hatch.

What did scientists still learn from Coquita’s baby?

A crocodile lying still on rocks by the water

American crocodiles like Coquita are at risk of becoming endangered.

How could testing eggs from crocodiles that live alone help American crocodiles?

A close-up of a crocodile in the water

A mixed pair is two different copies of a gene, like one working copy and one broken copy.

How is Coquita’s baby different from a clone?

A chart of all the chromosomes in one human cell

Lesson complete

Today’s word

parthenogenesis

par-theh-no-JEN-uh-sis

A baby grows from an egg that was never fertilized, meaning no sperm ever joined the egg.

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Up nextunisexualSome species are all female and they still make babies
Sources
  1. Booth and others, Biology Letters, 2023
  2. Card and others, Scientific Reports, 2021 (king cobra)
  3. Vision and Change core concepts and competencies, as summarized in Brownell and others, CBE Life Sciences Education, 2014
  4. Word origins from Dictionary.com: parthenogenesis, homozygous, gene, hydrogen
  5. Mark Cartwright, “Parthenon,” World History Encyclopedia
  6. Spanish and French spellings from Wiktionary