Argyropelecus affinis facts for kids
Quick facts for kids Argyropelecus affinis |
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Argyropelecus
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affinis
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The Argyropelecus affinis is a fascinating type of ray-finned fish. It belongs to a group often called "hatchetfish" because of their unique shape. You can find this fish in the warm, tropical, and subtropical parts of the Atlantic, Indian, and Pacific Oceans. People sometimes call it the Pacific hatchetfish, deepsea hatchetfish, or slender hatchetfish. It lives in the mesopelagic zone, which is a deep part of the ocean. This fish either stays at one depth or makes short daily trips up and down in the water.
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About the Slender Hatchetfish
The Argyropelecus affinis is a small fish. It can grow up to about 70 millimeters (or 2.7 inches) long. It looks very flat from side to side, almost like a hatchet blade.
What it Looks Like
This fish has a mouth that points upwards. Its eyes are also like tubes and point straight up. This helps it spot food or dangers above it in the dim ocean. It has a small spine near its gill cover.
Its fins are quite simple. The top fin (dorsal fin) has 9 soft rays. It also has a small, fatty fin called an adipose fin. The side fins (pectoral fins) have 11 or 12 rays, and the bottom fins (pelvic fins) have 6. The fin on its underside (anal fin) has 13 rays. It also has some short spines on its belly.
Inside, this fish has a well-developed swim bladder filled with gas. This helps it control its depth in the water. Its back is dark, and its sides are shiny silver. It has darker spots along its side. Its scales can fall off easily. Adult fish have special rows of photophores on their underside. These are organs that produce light.
Where it Lives and What it Likes
The slender hatchetfish lives all around the world in the warmer parts of the Atlantic, Indian, and Pacific Oceans. It is very common off the coast of West Africa. You can also find it as far south as Madagascar.
Its Ocean Home
This fish usually lives in the mesopelagic zone. This part of the ocean is sometimes called the "twilight zone." It's where some sunlight can still reach, but it's mostly dim.
During the day, you'll find most of these fish deeper down, usually between 350 and 600 meters (about 1,150 to 1,970 feet). But at night, many of them move up to shallower waters, between 170 and 400 meters (about 560 to 1,310 feet). This movement is called a diel vertical migration. It means they travel up and down each day.
What the Slender Hatchetfish Eats
Adult Argyropelecus affinis are not picky eaters. They feed on tiny creatures that float in the ocean, known as plankton. Their diet includes things like salps, krill, arrow worms, copepods, and ostracods.
Smaller hatchetfish mostly eat copepods and ostracods. The special light-producing organs on their belly start to fully develop when they are about 14 millimeters (or 0.55 inches) long.
Its Special Eyes
The eyes of Argyropelecus affinis have yellow pigments in their lenses. These pigments help to absorb certain types of light. Scientists are still studying exactly what these pigments do. However, by absorbing some light, the fish's eyes might be less sensitive to very bright light.
Its Conservation Status
The Argyropelecus affinis is a very common fish. It is found in large numbers across its wide ocean home. There are no known major threats to this species. Because of this, the International Union for Conservation of Nature has listed its conservation status as "least concern". This means it is not currently at risk of disappearing.
