Smalleye pygmy shark facts for kids

The smalleye pygmy shark (Squaliolus aliae) is a tiny, lesser-known shark. It is part of the Dalatiidae family. You can find it in the deep parts of the ocean near countries like Japan, the Philippines, and Australia. This shark lives very deep, usually between 150 and 2,000 meters (about 490 to 6,560 feet) below the surface. It moves up and down in the water every day, staying deep during the day and swimming closer to the surface at night. The smalleye pygmy shark is one of the smallest shark species in the world. It only grows to about 22 centimeters (8.7 inches) long. It has a dark, body shaped like a cigar, with small eyes. It also has a small spine in front of its first dorsal fin (the fin on its back). Its belly glows with special light-making organs called photophores. These lights might help it hide from other animals that want to eat it. This shark eats small sea creatures like squid, krill, shrimp, and tiny bony fishes. It gives birth to live young, just like some mammals. The International Union for Conservation of Nature says this shark is of "Least Concern". This means it is not currently in danger of disappearing.

Finding the Smalleye Pygmy Shark

The very first smalleye pygmy shark ever found was a female. She was about 18 centimeters (7.1 inches) long. Fishermen caught her near Donggang, Taiwan, in 1958. A scientist from Taiwan named Teng Huo-Tu studied this shark. He named it alii after a woman. Later, the name was changed slightly to aliae in science books.

Where Does This Shark Live?

The smalleye pygmy shark makes its home in the western part of the Pacific Ocean. You can find it in different places, including the waters off southern Japan, the Philippines, and northern and eastern Australia. This shark likes to live in the upper and middle parts of the ocean, not too far from land. It lives at depths from 150 to 2,000 meters (about 490 to 6,560 feet).

Daily Deep-Sea Travels

This shark goes on a daily journey up and down in the water. This special movement is called a diel vertical migration. During the day, it stays in the deeper, darker parts of the ocean. When night arrives, it swims up to shallower areas.

What Does the Smalleye Pygmy Shark Look Like?

This shark is one of the smallest sharks alive. It grows to a maximum length of about 22 centimeters (8.7 inches). Its body looks like a cigar, which means it's long and rounded. It has a round, pointed snout (its nose area). Its eyes are quite small and are shaped differently from other similar sharks.

Shark Teeth and Gills

The smalleye pygmy shark has many rows of teeth. It has 20 to 27 rows of teeth on its upper jaw. On its lower jaw, it has 18 to 23 rows. The teeth on its upper jaw are thin and stand straight up. The teeth on its lower jaw are wider and sharp like knives. They fit together to make a strong cutting edge, which helps it eat. This shark also has five pairs of very small gill slits, which it uses to breathe underwater.

Fins and Skin

This shark is special because it has a spine on its first dorsal fin (the fin on its back closest to its head). However, it does not have a spine on its second dorsal fin. The first dorsal fin is tiny. Its pectoral fins (the fins on its sides) are short and rounded. It does not have an anal fin (a fin on its underside near the tail). The caudal fin (tail fin) is wide and shaped like a triangle. Its skin is covered in flat, scale-like structures called dermal denticles.

Glowing Belly

The smalleye pygmy shark is dark brown to black in color. Its fins are a bit lighter at the edges. Its underside is covered with special organs called photophores. These organs can make light, which makes the shark's belly glow.

Life Cycle and What It Eats

Scientists do not know much about the daily life of this tiny shark. It mostly eats small animals that live in the middle of the ocean. These include squid, krill, shrimps, and small bony fishes like lanternfish.

How It Hides

The glowing organs on its belly might help it hide from predators. This is called "counter-illumination." The shark's light matches the dim light coming from above. This makes its outline harder for predators below to see, helping it blend in.

Reproduction

Like other sharks in its family, the smalleye pygmy shark gives birth to live young. This is called aplacental viviparous reproduction. The young sharks are born small, less than 10 centimeters (3.9 inches) long. Male sharks become adults when they are about 15 centimeters (5.9 inches) long.

Smalleye Pygmy Sharks and People

People do not often catch the smalleye pygmy shark. This is because it is so small. It also has no real value for fishing. Because it lives in many different places and is not often caught by fishing, the IUCN says it is of "Least Concern". This means it is not in danger of disappearing.