Longhead catshark facts for kids
Quick facts for kids Longhead catshark |
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Apristurus
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longicephalus
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| Range of the longhead catshark | |
The longhead catshark (Apristurus longicephalus) is a special type of catshark. It's also called the smoothbelly catshark. These sharks live in parts of the Indo-Pacific Ocean, from Mozambique all the way to southern Japan and northern Australia.
You can find them deep underwater, usually between 500 and 1,140 meters (about 1,640 to 3,740 feet) deep. The longhead catshark can grow up to 59 centimeters (about 23 inches) long. It's easy to spot because of its super long and thin snout. It also has a short belly and long fins, especially its anal and tail fins. A cool fact about this shark is that a big part of its front underside doesn't have the rough, tooth-like scales called dermal denticles.
This shark lays eggs, which is called being oviparous. It's also the only known cartilaginous fish (fish with skeletons made of cartilage, like sharks and rays) that is usually hermaphroditic. This means most of these sharks have working body parts for one gender and undeveloped body parts for the other.
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Discovering the Longhead Catshark
The very first longhead catshark ever studied was caught in Tosa Bay, Kōchi Prefecture, Japan. This happened on May 12, 1972. The shark was 38 centimeters long. At first, scientists thought it was a young male. But later, they realized it was a female that also had some male features.
A scientist named Kazuhiro Nakaya officially described this new species in 1975. He wrote about it in a science magazine called Memoirs of the Faculty of Fisheries, Hokkaido University. Later, in 1999, Nakaya and another scientist, Sato, grouped this shark with other long-snouted catsharks.
Where Longhead Catsharks Live
Longhead catsharks are found in many different places across the Indo-Pacific region. However, their sightings are spread out, meaning they are not found everywhere in between. They have been seen in the East China Sea, southern Japan, the Seychelles, the Philippines, Mozambique, New Caledonia, and northern Australia. In Australia, they've been spotted near Townsville, Ashmore Reef, and North West Cape.
These sharks live on the continental slope, which is the sloping part of the ocean floor that goes from the edge of the continent down to the deep sea. They prefer depths between 500 and 1,140 meters (1,640 to 3,740 feet). They probably spend most of their time near the bottom of the sea.
What the Longhead Catshark Looks Like
The longhead catshark can grow up to 59 centimeters (about 23 inches) long. It has a soft, very thin body. Its head is quite long, making up about a quarter of its total body length. The snout is flat and bell-shaped, and it gets much narrower in front of the nostrils. The snout itself is about 12% of the shark's total length.
Its nostrils are slanted and split into two openings. Small, oval eyes face slightly upwards. They have simple eyelids called nictitating membranes. Behind each eye, there's a small hole called a spiracle. The mouth is short and wide, with grooves at the corners. This shark has many rows of teeth, usually 36 to 44 in the upper jaw and over 45 in the lower jaw. Each tooth is spaced out and has three or five points, with the middle point being the longest. It has five short gill slits, with the last two pairs located above the base of its pectoral fins.
The first dorsal fin (on its back) is rounded and sits over the back part of its pelvic fins. The second dorsal fin is similar in shape but much bigger than the first. It's located over the back half of the anal fin. The pectoral fins (side fins) are medium-sized and wide. The rounded pelvic fins are also medium-sized and are quite close to the pectoral fins. The anal fin is long and angled, and it's separated from the caudal fin (tail fin) by only a deep notch. The tail fin is narrow and makes up about one-third of the shark's total length. It has a clear lower part and a small notch near the tip of the upper part.
The shark's skin feels velvety because of its tiny, spaced-out dermal denticles. Each denticle has a ridge in the middle and three points at the back. A large area of skin on its throat, gills, around its pectoral fins, and along its belly is smooth and doesn't have these denticles. The edges of its fins are also smooth. This shark is dark brown to blackish. The smooth skin patches and the inside of its mouth are black.
Life and Reproduction
The longhead catshark has a unique digestive system. Unlike other Apristurus species, its duodenum (part of the small intestine) is almost as long as its spiral valve intestine. Scientists are still trying to figure out why this is. We don't know much about what these sharks eat.
This catshark is special because it's the only known cartilaginous fish that is usually hermaphroditic. This means about 85% of these sharks have working reproductive parts for one gender, but also undeveloped parts for the other gender. Scientists are still studying why this happens.
The longhead catshark lays eggs. Only one partial egg case has ever been found. It had thin, curly parts on its back corners. Male longhead catsharks become ready to reproduce when they are about 42 to 49 centimeters (16.5 to 19 inches) long. Females are ready when they are around 51 centimeters (20 inches) long.
Longhead Catsharks and Humans
The longhead catshark isn't usually caught for food or other products, so it doesn't have much economic value. However, it might sometimes be caught by accident by fishing boats, which is called bycatch.
Even if deep-sea fishing becomes more common, this shark might be able to avoid being caught. It can probably swim to even deeper waters to stay safe. Because of its small size and the deep waters it lives in, the longhead catshark doesn't pose any danger to humans. For these reasons, its conservation status is listed as "Least Concern," even though we don't have a lot of information about its population numbers.
