Cherax tenuimanus facts for kids
Quick facts for kids Cherax tenuimanus |
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The hairy marron (also called the Margaret River marron) is a special type of crayfish found only in Southwest Australia. It's one of two kinds of crayfish known as marron in that area. This amazing creature lives in a small part of the Margaret River region.
Sadly, the hairy marron is currently listed as critically endangered. This means it's at a very high risk of disappearing forever. The main reason for this is another type of crayfish, the smooth marron (Cherax cainii), which was brought into the hairy marron's home. Scientists are looking for ways to help the hairy marron survive. For example, some studies show that adding a special supplement called mannanoligosaccharide (Bio-Mos) to their food can make them healthier and help them live longer.
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What Does the Hairy Marron Look Like?
The hairy marron can be many colors, from olive green to brown or even black. Female marrons sometimes have cool red or purple spots on their undersides. Adult hairy marrons can grow quite large, usually between 30 to 40 centimeters long.
Their body has two main parts: a head and a chest area, both covered by a hard shell called a carapace. Their body then stretches into a strong tail. They have five pairs of legs. Two of these pairs are pinchers! The bigger pinchers are used for catching food and defending themselves. The smaller pair helps them carefully handle their food.
You can tell a hairy marron apart from a smooth marron by the tiny, hair-like bristles that sometimes cover its shell and other body parts. These bristles can be hard to see on younger marrons.
What Do Hairy Marrons Eat?
Hairy marrons are omnivores, which means they eat both plants and animals. Their diet mostly includes small invertebrates (like insects without backbones), fish eggs, tiny fish larvae, and algae. Sometimes, they might even eat their own young!
Where Do Hairy Marrons Live?
Hairy marrons live only in freshwater. They need clear, oxygen-rich water, like the kind found in the Margaret River in Southwestern Australia. Because of competition with the smooth marron, their home range has shrunk. Now, they are mostly found in just three main pools in the upper part of the river.
Scientists don't know the exact perfect conditions for hairy marrons in the wild because there are so few of them left. However, studies done in special tanks (called aquaculture settings) show they do best in water that's about 25 degrees Celsius. They also prefer water with a certain amount of salt, at least 100 milligrams per liter. Hairy marrons also like places with debris or other structures. They use these as hiding spots or even as food if the material is organic.
Hairy Marron Life Cycle
Hairy marrons start to mate when they are about two or three years old. Their mating season usually happens between July and October. When it's time to reproduce, the female marron carries 200 to 400 eggs inside her for almost six months. Very large females can even produce up to 800 eggs!
After this, the female lays her eggs on tiny leg-like structures under her tail called swimmerets. The male then passes a sperm packet to the female, which she uses to fertilize the eggs. The eggs stay under the female's tail for several weeks. They hatch around or just after the end of the mating season. The baby marrons, called juveniles, stay attached to their mother's swimmerets until they've eaten all the yolk from their yolk sacs. This usually happens by November or December, when they are big enough to find their own food.
The smooth marron has a similar way of reproducing. However, there's some evidence that their breeding season starts earlier than the hairy marron's. This difference in timing might give the young smooth marrons a head start. They can grow larger before the young hairy marrons, which gives them an advantage in finding food and space.
The Smooth Marron Invasion
One of the biggest dangers to hairy marron in the wild is the smooth marron. The smooth marron was introduced into the Margaret River in the 1980s. From 1980 to 1992, the smooth marron slowly took over the lower parts of the river. By the year 2000, hairy marron were completely gone from the middle part of the river. Since then, smooth marron have always been found living alongside hairy marron in the upper parts of the Margaret River.
Scientists believe that smooth marron were first introduced in the lower parts of the river. From there, they spread to the middle and upper regions over time. They replaced the hairy marron through different ways, including competition for food and space, and even by interbreeding.
Hybridization: Mixing Species
In the past, hairy marron and smooth marron were thought to be two completely different species based on how they looked and their genetics. However, more recent research has found that they can actually breed with each other! And when they do, they can produce healthy babies that can also reproduce. This has led to a debate among scientists about whether they are truly separate species or not.
Even though they can interbreed, some scientists think there might be something that makes it harder for them to do so easily. This idea comes from research suggesting that interbreeding happens less often than it would if they were the same species.
Helping the Hairy Marron
Raising hairy marron in special farms (called aquaculture) is a small industry in Australia. The Australian Government is also using these farms to run a special breeding program. The goal is to raise hairy marron in captivity to help save the species.
Between 2013 and 2017, people tried to regularly remove smooth marron from the few pools where hairy marron lived. But it was decided that this wasn't helping enough to save the wild populations. Now, conservation efforts are focused on making the captive breeding program bigger. They are also looking for other safe places where the marron raised in captivity could be released back into natural water systems.
