Austrothelphusa transversa facts for kids
Quick facts for kids Austrothelphusa transversa |
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The Austrothelphusa transversa, also known as the freshwater crab, inland crab, or tropical freshwater crab, is a special type of freshwater crab. It lives only in Australia. This crab is very good at surviving dry conditions and droughts. This is why it can be found in many different parts of Australia.
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About the Inland Crab
The scientific name for this crab is Austrothelphusa transversa. Over time, scientists have changed its name and group several times. This happened because some original samples were lost. Also, it was hard to tell similar crabs apart. Now, with modern testing, it is part of the Austrothelphusa group. There are six other species in this group.
What Does It Look Like?
The inland crab's shell, called an carapace, can be different colors. It might be brown, maroon, or grey. Sometimes it's just one solid color. The shell is quite smooth. It can grow to about 5 cm (2.0 in) (2 inches) across.
Like other decapods (a group of ten-legged creatures), this crab has two claws. One claw is usually longer than the other. It also has four pairs of legs. Its body shape is generally round.
Where It Lives
The inland crab lives only on the Australian mainland. You can find it across the north-western half of Australia. This includes the dry inland areas of central Australia. It also lives in the tropical and sub-tropical rivers of northern Australia.
You will mostly find the inland crab in rivers, creeks, and waterholes that dry up. These are common in Queensland (QLD) and the Northern Territory (NT). You can also find smaller groups in north-eastern Western Australia (WA) and South Australia (SA). Some live in parts of north-western New South Wales (NSW).
How It Behaves
Sleeping Through Droughts
The inland crab has a special way to survive long dry periods. It goes into a deep sleep called aestivation. It builds deep burrows (tunnels) in clay or mud banks. It stays there, waiting for the rain to return. When the creeks and rivers fill up again, the crab comes out.
Building these burrows is very important for its survival. The burrows help the crab find moist soil closer to the underground water. This keeps them alive during the dry winter months. This is similar to what the common yabby does. These burrows are usually about 50–100 cm (20–39 in) (20–40 inches) deep. The crab puts a plug over the top of the burrow. This creates a sealed room that traps moisture. This helps the crab stay alive for a long time without water.
What It Eats
When the wet season brings water back to the rivers, there's lots of aquatic life. This includes algae and fish. The inland crab is an omnivore, meaning it eats both plants and animals. It mainly eats the algae that grows in the rivers when the water returns. The inland crab is also an opportunistic scavenger. This means it will eat decaying animals it finds.
Living on Land and Water
The Austrothelphusa transversa has special gills. These gills can work like lungs when the crab is out of water. This allows it to be amphibious, meaning it can live both in water and on land. Many other crustacean species also have this ability.
This adaptation helps the crab leave the water to control its body temperature. This is called thermoregulation. Small pools of water can get too hot or too cold during the day. So, the crab can leave the water and find shelter. It might hide among roots, fallen leaves, or other debris.
How It Reproduces
Female crabs carry their fertilized eggs under their abdomen (tail part). This part is tucked under the main body. A female can lay anywhere from 100 to 350 eggs. She holds onto the eggs as they develop. She also keeps the young crabs until they are small juveniles. Then, she releases them into the nearby area. They then have to find food and survive on their own.
It is believed that mother crabs hold onto their young during the aestivation period in the burrows. They release the young crabs when they come out of aestivation. This gives the young crabs the best chance to survive. They are released when waterways have returned and there is plenty of food.
Protecting the Inland Crab
The IUCN says the Austrothelphusa transversa is of 'Least Concern'. This means it is not currently at high risk of disappearing. It lives in several protected areas, like Sturt National Park. Its wide distribution is why it's considered 'Least Concern'. However, scientists are still studying it. They want to know if it will stay at this level in the future. Recent studies suggest that because it is so widespread, there might be more types of this crab than we currently know.
What Threatens Them?
Some things are threatening the inland crab. These include city growth and changes to natural rivers. When people change the natural flow of creeks or replace riverbanks with concrete, it hurts the crab. This makes it harder for them to burrow and aestivate.
Other threats include long periods of drought, farming activities, and climate change. These factors could mean the inland crab faces even longer times without water in the future.
