Gastrotrich facts for kids
Quick facts for kids Gastrotrichs |
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| Darkfield photograph of a gastrotrich.. | |
| Scientific classification | |
| Kingdom: | |
| Subkingdom: | |
| Superphylum: |
Platyzoa
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| Phylum: |
Gastrotricha
Metschnikoff, 1864
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The Gastrotricha, often called hairy backs, are tiny animals. You need a microscope to see them! They are usually between 0.06 and 3.0 millimeters long. These creatures live in many places. You can find them in fresh water and in the sea.
Sea species often live between tiny bits of sand and mud. Land species live in the thin water layers around soil grains. There are about 700 different kinds, or species, of gastrotrichs known.
Body and Features
Gastrotrichs have bodies that are symmetrical on both sides. This means if you cut them down the middle, both halves would look the same. Their bodies are clear, and they have a flat underside. Many kinds have two short parts that stick out from their back end.
Their bodies are covered with tiny hairs called cilia. These cilia are especially thick around their mouth and on their bottom side. The two parts sticking out from their back end have special "cement glands." One gland makes a sticky glue. Another gland makes a substance that unglues them. This helps them stick to things and then let go easily.
Like many tiny animals, gastrotrichs move mostly by using water pressure inside their bodies. They have a set number of cells when they are adults. They grow bigger by their cells getting larger, not by making more cells.
Because they are so small, gastrotrichs do not need special organs for breathing or for moving blood around. They likely get rid of waste through their body surface. Their nervous system is quite simple. They have a small "brain" made of two nerve clusters, one on each side of their throat. From these clusters, a single nerve cord runs down their body.
Their main sense organs are the bristles and tiny hair tufts on their body. Some gastrotrichs also have simple light-sensing cells in their brain. These are like very basic eye spots.
Reproduction and Life Cycle
Gastrotrichs are special because they are hermaphrodites. This means each animal has both male and female parts. After they make sperm, they use a special organ on their tail to pass it to another gastrotrich. The eggs are fertilized inside the body. Then, the eggs are released when the body wall breaks open.
Many species of gastrotrichs can reproduce all by themselves. This is called parthenogenesis. In these species, the male parts of their body do not work, or they are not even there.
Some gastrotrichs can lay special eggs that can wait for a long time. These eggs can survive when it is dry or cold. When conditions are good, these species lay normal eggs. These eggs hatch in about one to four days. The young gastrotrichs that hatch look like tiny versions of the adults. They usually become ready to reproduce in about three days. In a lab, gastrotrichs can live for up to ten days.
Images for kids
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Lepidodermella squamata (a type of Chaetonotida)
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Diplodasys rothei
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A & B = Macrodasyida C, D, E & F = Chaetonotida
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Ptychostomella sp., a type of Macrodasyida
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See also
In Spanish: Gastrotricha para niños
