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Spotted ratfish

life science Maturity 5-7 Next article →

The spotted ratfish, known scientifically as Hydrolagus colliei, is a unique cartilaginous fish.

Hydrolagus colliei 03
Hydrolagus colliei 03

It belongs to a group called chimaeras. These animals are found in the northeastern Pacific Ocean. Their range stretches from Alaska down to Baja California. They are most common in the Pacific Northwest. These fish are not typically eaten by humans. They are also not caught for commercial fishing. They are important to study because they show how different fish families evolved.

The ratfish has a very distinct body structure. Its skeleton is made of cartilage rather than bone. This makes the body flexible. The fish has a duckbill-shaped snout and a face that looks like a rabbit. Large pectoral fins extend from its sides. These fins look like airplane wings. The fish uses them to swim in barrel rolls and corkscrew turns. This movement is often called aquatic flight.

Hydrolagus colliei1
Hydrolagus colliei1

A long, pointed tail makes up almost half of its total length. This tail resembles the tail of a rat. The skin is smooth and lacks scales. It is silvery-bronze with gold, blue, and green shades. White spots cover its back, which gives it its name.

Feeding is a specialized process for the spotted ratfish. It has a small mouth and a snout shaped like a duckbill. Unlike sharks, which have replaceable teeth, the ratfish has permanent teeth. These teeth are mineralized, plate-shaped structures.

Hydrolagus colliei teeth
Hydrolagus colliei teeth

They stay in the mouth for the fish's entire life. These plates help the fish grind up crunchy prey. The ratfish has the largest biting force in the Holocephali group. This allows it to eat large, hard foods. It uses its sense of smell to hunt at night. Its diet includes crabs, clams, shrimp, worms, and sea stars.

Reproduction in ratfish is a slow and careful process. They are oviparous, which means they lay eggs.

Hydrolagus colliei1
Hydrolagus colliei1

Spawning peaks between spring and autumn. A female releases up to two fertilized eggs every 10 to 14 days. The extrusion process can take 18 to 30 hours. The actual laying of eggs can last 4 to 6 days. The eggs are held in leathery cases. Each case has a filament to attach it to the sandy or muddy seafloor. This prevents the eggs from floating away. It can take up to one year for the eggs to hatch. When they do, the young are about 10 centimeters long.

Male spotted ratfish have unique physical features for mating. They possess pelvic claspers to move sperm to the female.

Highlighted Frontal Tenaculum of Spotted ratfish Chimaera
Highlighted Frontal Tenaculum of Spotted ratfish Chimaera

They also have a unique organ called a cephalic clasper. This is a club-like organ located on the head near the eyes. It is not found in any other vertebrate. The tip of this organ is fleshy and has small, sharp barbs. During courtship, the male may use this to clamp onto the female's pectoral fin. Because of this, females often have scars or scratches on their bodies. Males are also significantly smaller than females.

Spotted ratfish live in specific environments to survive. They prefer the seafloor in sandy, muddy, or rocky reef areas. Most live in deep water, but they move to shallower areas in the north. They also move between depths based on the seasons. In spring and autumn, they move closer to the shore. In summer and winter, they move to deeper water. They prefer water temperatures between 4 and 12 degrees Celsius. They can be found at various depths, but they are most common between 200 and 500 meters.

Hydrolagus colliei 03
Hydrolagus colliei 03

Even though they live in the deep, they are well-known to science. Scientists have even kept and bred them in public aquaria. This is difficult because they need low light and low temperatures. They are also known for their large, emerald green eyes. These eyes can reflect light just like a cat's eyes. This helps them see in the dark. While they are generally not aggressive, they have a defense mechanism. A venomous spine is located on the leading edge of their dorsal fin. This spine can cause painful wounds to humans or animals.

Holocephali skull structures
Holocephali skull structures
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🖼️ Images & Media (5)
File:Hydrolagus colliei 03.jpg
Hydrolagus colliei 03.jpg
File:Hydrolagus_colliei_teeth.jpg
Hydrolagus_colliei_teeth.jpg
File:Holocephali_skull_structures.png
Holocephali_skull_structures.png
File:Hydrolagus colliei1.jpg
Hydrolagus colliei1.jpg
File:Highlighted Frontal Tenaculum of Spotted ratfish Chimaera.png
Highlighted Frontal Tenaculum of Spotted...
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