Australian weasel shark facts for kids
Quick facts for kids Australian weasel shark |
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Hemigaleus
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| Species: |
australiensis
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| Range of the Australian weasel shark | |
The Australian weasel shark (Hemigaleus australiensis) is a type of shark that lives in the ocean. It belongs to a group called "ground sharks." These sharks are not very common. They live in shallow waters off northern Australia. You can find them as deep as 170 meters (558 feet).
Younger sharks like sandy areas with seagrass. As they get older, they move to coral reefs. This shark is slim and can grow up to 1.1 meters (3.6 feet) long. It has curved, sickle-shaped fins. The tips of its second dorsal fin and upper tail fin are often dark. Its upper teeth are wide and have strong jagged edges on one side. A clear line, called the lateral line, runs along its body. This line helps the shark sense movement in the water.
The Australian weasel shark mainly eats octopuses and other creatures like squid (called cephalopods). It usually hunts near the sea floor. This shark gives birth to live young, just like mammals. The baby sharks grow inside the mother, connected by something like a placenta. They are born after about six months. Female sharks can have many babies, usually 1 to 19 pups, and often twice a year!
People catch these sharks when fishing for prawns or other fish. They are caught with trawl nets, gillnets, and longlines. However, not too many are caught, so their population is not in danger. Because of this, the International Union for the Conservation of Nature (IUCN) lists the Australian weasel shark as "Least Concern." This means it's not currently threatened.
Contents
Discovering the Australian Weasel Shark
For a long time, people thought the Australian weasel shark was the same as another shark called the sicklefin weasel shark. But in 1983, two scientists, John Stevens and Glen Cuthbert, thought it might be a different species.
Later, in 2005, three scientists named William White, Peter Last, and Leonard Compagno officially described it as a new species. They wrote about it in a science magazine called Zootaxa. They named it australiensis because it lives in Australia. The first shark they studied to describe the species was a male, 92 cm (36 inches) long. It was caught off Geraldton, Western Australia.
What Does the Australian Weasel Shark Look Like?
The Australian weasel shark can grow up to 1.1 meters (3.6 feet) long. It has a thin, sleek body and a head that is quite long with a rounded snout.
Eyes and Mouth
Its eyes are large and oval-shaped. They have special eyelids called nictitating membranes that can cover the eye for protection. Behind and above its eyes are tiny holes called spiracles. Its nostrils are large and have small, triangular skin flaps in front of them. The shark's mouth is short and curved, with grooves at the corners.
It has many rows of teeth: 28–30 rows in the upper jaw and 46–52 rows in the lower jaw. You can't see its teeth when its mouth is closed. The upper teeth are wide and angled, with jagged edges only on the back side. The lower teeth are thin and straight with smooth edges. It also has five pairs of short gill slits for breathing.
Fins and Skin
All of the shark's fins are somewhat curved, like a sickle. This is especially true for its narrow pectoral fins (the ones on its sides). The first dorsal fin (on its back) is medium-sized. It starts just behind the tips of the pectoral fins. The second dorsal fin is about two-thirds as tall as the first. There is no ridge running along its back between the two dorsal fins.
Its pelvic fins (near its belly) are wide and a bit bigger than the anal fin (near its tail). The anal fin has a strong notch in its back edge and is placed slightly behind the second dorsal fin. The part of the body before the tail, called the caudal peduncle, has a crescent-shaped notch. The tail fin is not symmetrical. It has a well-developed lower part and a long, narrow upper part with a notch near the tip.
The lateral line is very noticeable and curves downward below the second dorsal fin. The shark's skin is covered in tiny, overlapping scales called dermal denticles. Each scale has five ridges that lead to small teeth. The shark is light grey to bronze on top. The tips of its second dorsal fin and upper tail fin are darker, but this might be hard to see in bigger sharks. Its underside is off-white, and the first dorsal fin has a pale back edge.
Where Does the Australian Weasel Shark Live?
The Australian weasel shark lives on the continental shelfs off northern Australia. This area stretches from Geraldton in Western Australia to Brunswick Heads in New South Wales. There might be some in Papua New Guinea, but this has not been fully confirmed. This shark is naturally quite rare.
It usually swims close to the sea floor. You can find it in shallow waters near the shore, all the way down to 170 meters (558 feet) deep. Young sharks and smaller adults prefer sandy areas with seagrass. Larger adult sharks are more often found around coral reefs.
Life and Habits of the Australian Weasel Shark
The Australian weasel shark mostly eats octopuses, like those from the Callistoctopus group. It might swallow them whole or pull off their arms first. As the shark gets older, octopuses become even more important to its diet. Sharks over 90 cm (35 inches) long eat almost nothing else! This change in diet comes with a move to coral reefs. This might help older and younger sharks avoid competing for the same food.
Sometimes, especially for smaller sharks, bobtail squids are a small part of their diet. Very rarely, they might eat other cephalopods, mud lobsters, crabs, or echinoderms (like sea urchins). This shark probably hunts mostly at dawn and dusk. It usually looks for prey that lives on the bottom of the ocean. But it will also swim higher into the water column if there's a chance, like when many broad squid gather together.
Reproduction
Like other sharks in its family, the Australian weasel shark is viviparous. This means the baby sharks grow inside the mother's body. They get food and oxygen through a connection similar to a placenta. Female sharks have one working ovary and two working uteruses.
The babies grow for six months. Females usually have two litters of pups each year. One litter is born around February, and the other around September. The number of pups in a litter can be from 1 to 19, but on average, it's about 8 pups. The baby sharks lose their external gills when they are about 13 cm (5 inches) long. They get their color by the time they are 23 cm (9 inches) long. They are born when they are about 30 cm (12 inches) long. Males become ready to have babies when they are about 60 cm (24 inches) long. Females are ready when they are about 65 cm (26 inches) long.
Australian Weasel Shark and Humans
The Australian weasel shark is harmless to humans. People often catch them by accident when fishing for prawns or other fish off northern Australia. They are caught using large nets called trawls. Some are also caught in gillnets and on longlines.
This shark has a good number of babies, and not too many are caught by fishing. So, its population is not seriously affected. Because of this, the International Union for the Conservation of Nature (IUCN) has listed the Australian weasel shark as "Least Concern." This means it is not considered an endangered species.
See also
In Spanish: Hemigaleus australiensis para niños
