Chimaeras are interesting fish that live in the depths of the seas, carrying a web of lines on their surface that resembles seams. These lines often cause parts of other creatures to appear as if they were put together, almost reminiscent of the Chimera in Ancient Greek mythology.
Notable features of a chimaera include large eyes and a broad snout in front of them. This nose has an interesting structure resembling a duck's beak. Some species of chimaera are also called "ratfish" because their bodies are arranged in a long, rat-like tail, with fangs reminiscent of mouse teeth. Others are known as "rabbit fish", and in some species the tip of their snout has a curved structure resembling the trunk of a miniature elephant, hence the name "elephant fish".
Chimaera are known for their large pectoral fins that allow them to fly through the water. Many species carry a sharp venomous spine in front of the first dorsal fin on top of their bodies. The chemicals released by this spine are considered mildly toxic to humans and can cause painful injuries.
Biological Classification of Chimaeras
Chimaera are related to sharks, but they have distinctive features and often look quite different from sharks. Both chimaeras and sharks have cartilaginous skeletons, and according to the traditional classification, all cartilaginous fish belong to the class Chondrichthyes. This class is divided into two subclasses: the Elasmobranchii subclass, which includes sharks, skates, and rays, and the Holocephali subclass, which includes chimaeras.
The subclass Holocephali includes only one order called Chimaeriformes.
Chimaera Features
The large eyes of the ratfish allow them to absorb light to the maximum in deep, dark waters. The eyes contain a membrane called the tapetum lucidum, which reflects light back to the retina, creating a luminous effect in dark environments. This feature can help with food hunting, especially in dim light.
Fish have three pairs of dental plaques in their mouths that help them effectively grind their crustacean prey. The lateral lines form the lateral line system that detects vibrations and movements in the water. On the front and bottom of the head, the line turns into a series of dots, which are the sensory structures that detect electric fields.
Where Does the Chimaera Live and What Does It Eat?
Most chimaera species live in the deep sea and are therefore often difficult to observe. However, the spotted ratfish is usually found in shallow waters and is more easily observed. These species are usually seen in groups, but they can also hunt individually. They tend to feed at night in conditions such as a lack of beneficial light. Their mouths point downward, which helps them gather food from the seafloor.
Fish usually detect their prey by smell. They also have the ability to detect weak electric fields, which helps them hunt for food, especially in dim light conditions.
Mating and Egg Production
Chimaeras work like any other cartilaginous with an internal fertilization system. The male has appendages called "clasper" next to his pelvic fins to insert sperm into the female fish's body. The male mousefish has an appendage called the "tentaculum" on its forehead, which is used to hold the female in place during mating.
The female mousefish produces a spindle- or spoon-shaped egg capsule that is about 5 centimeters long and has a leathery texture. It takes about 18 to 30 hours to eject the egg, and some of that time allows the capsule to hang by a filament from the female's body. Eventually, this capsule falls to the seaweed or ocean floor and sticks to its surroundings. The egg laying rate is low because a female lays only two eggs, although more than one spawning event can occur in a year.
The young fish are approximately 5 centimeters long when they emerge from the capsule. In the first months after their debut, these youngsters develop very slowly and are unable to leave the capsule for up to a year.
