Astyanax abramis facts for kids

Quick facts for kids Astyanax abramis
Scientific classification
Genus:	Astyanax
Species:	abramis

Astyanax abramis is a small freshwater fish. It lives in rivers across much of South America. You can find it in places like the La Plata, upper Amazon, and Meta River basins. This fish has a somewhat diamond-shaped body that is flattened from side to side. Its scales are mostly silver, with hints of blue or green on its back.

Sometimes, A. abramis is called a cryptic species. This means it might actually be several different species that look very much alike. They are so similar, scientists haven't fully described them all yet. A. abramis is also part of a group called a species complex. This group includes other fish like Astyanax bimaculatus and Astyanax lacustris. These fish are very closely related and look quite similar. The Astyanax group has many species, and it's common to find these "hidden" species or complexes within it.

What Does Astyanax abramis Look Like?

Astyanax abramis is a small fish. The longest one ever found was about 14.0 cm (5.5 in) long. It weighed about 29.70 grams. Its body is flat on the sides and shaped a bit like a diamond. This fish is silvery, with a green or blue shine on its back.

It has a dark spot near its tail, starting at the base of the tail fin. This spot goes all the way to the end of the tail fin. Its fins are mostly clear, but they can have a slight red, orange, or yellow color.

Special Markings and Features

There is a dark spot on each side of the fish, behind its head. This spot is shaped like a horizontal oval. This area also has two brown vertical bars. A black stripe runs along its side, just above its lateral line. This stripe starts at or just behind the dark oval spot.

A. abramis has one spine and 10 rays in its dorsal fin. It also has 30 to 34 rays in its anal fin. It has 42 to 48 scales along its lateral line. This helps tell it apart from a similar fish, A. lacustris, which has fewer scales (36 to 39). Its scales are generally small. A. abramis does not have teeth in its upper jaw (maxillary teeth). This helps identify it from other similar fish. However, it does have teeth in its premaxilla (front part of the upper jaw). Scientists believe it can replace missing teeth one by one.

How Males and Females Are Different

It's hard to tell male and female A. abramis apart just by their body shape. However, male fish have small hooks or barbs on their anal-fin rays. Females do not have these hooks. Also, there are usually more female fish than male fish.

How Scientists Classify Astyanax abramis

When A. abramis was first described, it was named Tetragonopterus abramis. An English scientist named Leonard Jenyns gave it this name in 1842. He used fish collected by the famous natural historian Charles Darwin in the 1800s. At one point, it was called a different species, Bertoniolus paraguayensis. But now, scientists agree it's the same as A. abramis. In 2016, its classification as a valid species was confirmed.

The Astyanax group has three main subgroups. These are Astyanax strictu sensu, Poecilurichthys, and Zygogaster. A. abramis belongs to the Poecilurichthys subgroup.

Many species in the Astyanax group are considered cryptic. This means they look so much alike that they are currently considered one species. But they actually cannot reproduce with each other. A. abramis is one of these cryptic species. It is also part of the Astyanax bimaculatus species complex, along with Astyanax lacustris.

When Jupiaba abramoides was first described, scientists thought it was closely related to A. abramis. That's why its name includes "oides," which means "having the shape of." The original name for J. abramoides was actually Astyanax abramoides.

What Does the Name Mean?

The specific name "abramis" refers to a European fish called Abramis brama. This fish has a similar body shape to A. abramis. The genus name "Astyanax" comes from a character in an ancient Greek story, Homer's Iliad. Astyanax was the son of Hector, a famous warrior from Troy. It's not clear why the fish group was named after him. It might be because of the large, armor-like scales of another fish in the group, A. argentatus.

A common name for A. abramis, and many other Astyanax species, is "lambari."

Where Does Astyanax abramis Live?

Astyanax abramis can be found in the La Plata basin. It also lives in the upper Amazon and Meta River basins. This fish prefers still water environments, like ponds or slow-moving parts of rivers. Still water often has less oxygen. Because of this, A. abramis has developed ways to adapt to low-oxygen conditions. It can even change its body shape a little to help.

Its home stretches across several countries. These include Brazil, Argentina, Bolivia, Uruguay, and Paraguay. You can find it in specific rivers and areas like the Juramento, Yabotí, and Parana rivers.

How Astyanax abramis Lives and Behaves

When there's very little oxygen in the water, A. abramis can grow temporary skin extensions. These might help it breathe better by taking oxygen from the water's surface. Scientists have seen similar changes in other fish that live in low-oxygen places. This ability to breathe at the surface helps many fish survive in tough environments.

Astyanax abramis lives in the same places as its close relative, A. lacustris. It also shares its habitat with other similar fish. These include A. puka, A. asuncionensis, A. eigenmanniorum, and A. lineatus. They all live together in rivers like the Juramento River. A. abramis eats many different things, including other fish. So, it probably doesn't live with very small fish.

Astyanax abramis can also get parasites. A type of parasitic worm called Procamallanus (Spirocamallanus) hilarii has been found in A. abramis. This worm is found in many different fish species in South America.

Reproduction and Life Cycle

Astyanax abramis has two main times of the year when it reproduces. These are in April and October. These months usually have warmer water temperatures and more rain. In female fish, larger bodies are linked to larger ovaries. This means that during these active reproduction periods, you're likely to find more large female fish.

What Does Astyanax abramis Eat?

Astyanax abramis is a very flexible omnivore. This means it eats both plants and animals. It lives in areas that often have floods. During times when food is scarce, its intestines can grow larger. This helps it digest foods that are usually harder to break down, like plant material. Younger fish are smaller, so they don't have as much flexibility. They sometimes eat more meat than the adult fish.

Other studies suggest that young fish might eat more plants than adults. This likely depends on the environment. For example, if there are many plants along the river, A. abramis might eat more plants. This means what A. abramis eats can change depending on where it lives. Also, smaller adult fish tend to eat more meat than larger adults. This adds to the variety of their eating habits.

Is Astyanax abramis Endangered?

The IUCN (International Union for Conservation of Nature) has not yet checked on Astyanax abramis. However, it is found in many places and is easy to find. So, it is most likely a species that is not in danger. For example, in one study of fish in the Yabotí stream, A. abramis was the ninth most common species. The Yabotí stream is mostly inside the protected Yabotí Biosphere Reserve.

Images for kids

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  An Astyanax abramis fish.

See also

In Spanish: Astyanax abramis para niños