Australian scientists have made a world-first “very unusual discovery”.
Researchers at the University of Sydney have witnessed an Australian lizard lay three eggs first and then, weeks later, give birth to a live baby from the same pregnancy. In the past, this particular lizard has given birth to baby lizards rather than laying eggs.
It’s the first time such a strange event has been seen in a single litter of vertebrate babies, or animals with backbones.
The lizard is a three-toed skink. The species is one of only a handful of rare “bimodally reproductive” species. Bimodally means in two ways. Bimodally reproductive* means some individuals of the species lay eggs and others give birth to live babies.
But until now no vertebrate has ever been seen doing both in one litter.
“It is a very unusual discovery,” said Dr Camilla Whittington of The University of Sydney.
The three-toed skink is native to the east coast of Australia.
In the northern highlands of New South Wales the animals normally give birth to live young, but those living in and around Sydney lay eggs.
Previous research has shown that if a Sydney skink was taken north it would still lay eggs, while live bearers moved to Sydney would also continue to reproduce as they previously did.
“We were studying the genetics* of these skinks when we noticed one of the live-bearing females lay three eggs,” Dr Whittington said.
“Several weeks later she gave birth to another baby. Seeing that baby was a very exciting moment.”
Dr Whittington said there were at least 150 evolutionary* steps between egg laying to live-bearing of babies in vertebrates.
“The earliest vertebrates were egg layers, but over thousands of years, developing embryos* in some species were held inside the body for longer until some animals began to give live birth,” she said.
“People mostly think about humans and other mammals giving birth. But there are many species of reptile that give birth, too.”
Dr Whittington said the unusual observation in a single litter showed the three-toed skink was an ideal model for understanding pregnancy.
“It makes Australia one of the best places in the world to study the evolution of live birth because we can watch evolution in action,” she said.
“Put in the context* of evolutionary biology*, being able to switch between laying eggs and giving live birth could allow animals to hedge their bets* according to environmental conditions.”
She said it also made the skink, which looked like a baby snake with tiny legs, one of the “weirdest lizards in the world”.
The University of Sydney study was published in the journal Biology Letters this week.
More research into this small lizard will help us understand how and why species change the way they reproduce* as they evolve.
VIDEO: Chameleons like this one at Western Plains Zoo, Dubbo, NSW, have evolved to be able to swivel their eyes in any direction without moving their heads
- reproductive: relating to the process of having babies
- genetics: study of how things are inherited from parent to baby
- evolutionary: relating to the process a species changes to adapt to the environment
- embryos: unborn babies
- context: the situation or setting
- biology: science of living things
- hedge their bets: a saying meaning
- reproduce: make more, such as babies or copies of something
- What type of lizard is this story about?
- What university did this research?
- Are mammals the only group of animals that give birth to live young?
- What does “hedge your bets” mean?
- What would more research on the lizard help us understand?
LISTEN TO THIS STORY
1. WORLD FIRST!
What an exciting discovery! Pretend you are a television news reporter for a Kids News program.
Work with a partner to write a script for a segment on this amazing lizard. In your segment, make sure you explain what has happened and why it is significant. During the segment, interview a researcher from the university, asking them questions that help to clarify the story.
Practice presenting your news segment and perform it to your class when you are satisfied with it.
Time: allow 45 minutes to complete this activity
Curriculum Links: English, Science, The Arts — Drama, Media
The article suggests that being able to produce live young and lay eggs could mean these lizards can choose the best method of reproducing, depending on environmental conditions.
Think from a lizards’ perspective: which environmental conditions would be more conducive to live births and which would be better for egg laying? Giving birth to live young means the mother must carry the baby (babies) inside her for longer (and feed them etc) while laying an egg may mean that someone has to keep the eggs safe.
Draw up a two columned chart titled LIVE BIRTH and EGG LAYING
Under each write the benefits to the mother, the babies and the species as a whole for each type of birth.
Time: allow 20 minutes to complete this activity
Curriculum Links: English, Science
An adjective is a word used to describe a noun. Go through the text and highlight all the adjectives you can find. Are they well chosen? Could you choose better?
See if you can up-level 3 of the adjectives from the text.
HAVE YOUR SAY: What special skill that another species has would you choose for yourself? Fly? Breathe underwater? Hibernate? It can be anything another animal has evolved to be able to do that humans can’t.
No one-word answers. Use full sentences to explain your thinking. No comments will be shown until approved by editors.