18 September 2015
  Science by Email  
News: Robot assassin protects the reef    

The crown-of-thorns is a venomous starfish that lives in the Great Barrier Reef. Growing up to massive lengths of 80 centimetres and having a body entirely covered in toxic spikes, the starfish is almost indestructible and is a vicious predator. They eat coral, the building blocks of the Great Barrier Reef. It’s said that one adult starfish can eat up to ten square metres of coral every year.

Recently populations of crown-of-thorns starfishes have been exploding and as a result the corals are in more danger than ever. The starfish are responsible for causing 40 per cent of all coral damage, making them one of the biggest threats to the Great Barrier Reef today.
But hope is not lost for the coral reef. Scientists Matthew Dunbabin and Feras Dayoub created an autonomous robot called COTSbot to minimise crown-of-thorns starfish populations and rescue the reef.
The robot is equipped with a number of thrusters and stereoscopic cameras, allowing it to search for the venomous starfish and kill them. Matthew and Feras trained the COTSbot through various YouTube videos, as well as thousands of images of the starfish by divers currently doing manual injection of the starfish on the Great Barrier Reef.
The COTSbot was trained for six months, to the point where it can identify crown-of-thorns starfish on its own. Once the starfish has been identified, the robot then injects it with bile salts, a protein that kills the starfish. The COTSbot can inject up to two hundred starfish and remain in the water for up to eight hours. Scientists hope that the COTSbot will be able to help protect corals and save the Great Barrier Reef.


More information

New robot fights crown of thorns starfish
A robot’s eye view

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Crown of thorns starfish on reef with target and needle.
Credit: Feras Dayoub, QUT
CSIRO Children’s books  
Phasmid book cover.

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Try this: Cool crystals  
Filling a cup with water from the tap.
Put the Epsom salt, hot water and food colouring into a cup and stir until dissolved.
Pouring Epsom salts into cup of blue water.
It is OK if Epsom salts are not entirely dissolved. Place the cup into the refrigerator for three hours.
Crystals forming in a cup of blue water.
After three hours you should be able to see crystals at the bottom of your cup.
Blue crystals in the bottom of a cup.
Carefully pour the water into the sink to get a better look at your crystals.

You will need

  • Cup or mug
  • ½ cup Epsom salt
  • ½ cup hot water
  • Food colouring (optional)
  • Spoon
  • Refrigerator

What to do

  1. Put the Epsom salt and hot water in the cup.
  2. If you want colourful crystals, add two drops of food colouring.
  3. Stir the solution in the cup for five minutes until most of the Epsom salt has dissolved. It is okay if the salt has not entirely dissolved.
  4. Once the salt has dissolved, place the cup into the refrigerator for three hours.
  5. After three hours, you should be able to see crystals at the bottom of your cup. Carefully pour the water into the sink to get a better look at your crystals.
  6. When you are finished, you can dispose of the crystals in the garbage and wash the cup well.

What’s happening?

Epsom salts dissolve in hot water. In chemistry terms, our solvent is water and our solute is Epsom salt, also known as magnesium sulfate.
Once you place the cup into the cool environment of the refrigerator, the warm solution inside the cup gets colder. Cold substances have less energy than hot substances, so the salt molecules don’t move around as much and they start to connect. Magnesium sulfate joins together in an ordered pattern, causing crystals to form.

More information

What are crystals?

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    Quiz questions    
  1. True or false? A lobster’s blood is blue when exposed to oxygen.
  2. Which element makes up majority of air in our atmosphere?
  3. Where are most of Earth’s active volcanoes located?
  4. What is the name of Neptune’s largest moon?
  5. What is the largest muscle in the human body?

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Double Helix magazine is looking for new questions for our Q&A section – Microscope. We take a close look at small questions full of big ideas. If you have a nagging little query that needs an answer, send it in!
Email with your question.


See it!

Astronaut Scott Kelly takes amazing photos while aboard the ISS.

Do it!

Ever want to study the stars? Here are ten steps you can take to become an awesome astronomer!

Watch it!

Different cultures have different stories about the stars. Here is a South African story about the constellation we call Orion.
Screenshot of the constellation Orion.
    Quiz answers    
  1. True. A lobster’s blood is blue when exposed to oxygen.
  2. Nitrogen makes up about 78% of air.
  3. Most of the active volcanoes on Earth are located in the Ring of Fire around the edge of the Pacific Ocean.
  4. Triton is Neptune’s largest moon.
  5. The gluteus maximus, or the buttocks muscle, is the largest muscle in the human body.